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User's Guide of SWAP version 2.0

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1. Section 1 Crop development If IDEV 1 specify LCC 168 Length of crop cycle 1 366 days I f IDEV 2 specify TSUMEA 1050 0 Temperature sum from emergence to anthesis 0 10000 C R TSUMAM 1000 0 Temperature sum from anthesis to maturity 0 10000 C R TBASE 0 0 Start value of temperature sum 10 20 C R
2. 0 1 cm R Section 6 Hysteresis of soil water retention function SWHYST 0 Switch hysteresis 0 no hysteresis 1 hysteresis initial condition wetting 2 hysteresis initial condition drying Tf SWHYST 1 or 2 specify TAU 0 2 Minimum pressure head difference to change wetting drying RARA KC Section 7 Similar media scaling of soil hydraulic functions SWSCAL 0 Switch similar media s
3. Section 4 Green surface area List specific leaf area ha kg R as function of development stage 0 2 R DVS SLA maximum 15 records SLATB 0 00 0 0020 2 00 0 0020 End of table SPA 0 0 Specific pod area 0 1 ha kg R SSA 0 0 Specific stem area 0 1 ha kg R SPAN 35 0 Life span of leaves at optimum conditions 0 366 d R TBASE 0 0 Lower threshold temperature for ageing of leaves 10 30 C R
4. Section 6 Conversion of assimilates into biomass CVL 0 685 Efficiency of conversion into leaves 0 1 kg kg R CVO 0 709 Efficiency of conversion into storage organs 0 1 kg kg R CVR 0 694 Efficiency of conversion into roots O kg kg R CVS 0 662 Efficiency of conversion into stems 0 1 kg kg R File wheatd crop detailed crop growth sections 2 6 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 9 RA
5. Section 1 Environment Project Hupsel Generic name for SWA SLT and HEA files A8 Path Path to data directory A50 CType 1 Switch computer type PC 1 VAX 6 Workstation 2 SWSCRE 1 Switch display progression of simulation run Y 1 N 0 How Wow Section 2 Time variables RUN ESRUN MA Y ER RE SWODAT 01 01 1980 Start date of simulation run give day month year 31 31 12 1980 1 End date of simulation run give day month year 31 0
6. Section 1 Top boundary and initial condition CPRE 0 Solute concentration in precipitation 0 100 mg cm3 R List initial solute concentration of each comp max 40 0 1000 mg cm3 R CMLI 0 0 4 0 0 Or 0 0 D s i 0 0 0 0 0 0 0x0 0 0 O 0 0 0 0 0 0 O 0 0 09 0 0 0 0 0 050 0 70 gt 0 0 0 0 0 0 0 0 KKK Ck Ck CK CK CK Section 2 Diffusion dispersion and solute uptake by roots DDIF Ds Molecular diffusion coefficient 0 10 cm2 day R LD
7. Section 4a Miscellaneous parameters WLACT 1123 0 initial surface water level ALTCU 1000 ALTCU cm R OSSWLM 2 5 criterium for warning about oscillation 0 10 cm R KKK Kk AAA AAA DA E RS Section 4b management of surface water levels NMPER 4 number of management periods 1 10 I For each management period specify IMPER index of management period 1 NMPER I IMPEND date that period ends dd daynumber 1 31 I 2 mm monthnumber 1 12 1 SWMAN type of water management 1 2 I 3 1 fixed weir crest 2 automatic weir WSCAP surface water supply capacity 0 100 cm d R WLDIP allowed dip of surf water level before starting supply 0 100 cm R INTWL length of water level adjustment period SWMAN 2 only 1 31 d R IMPER IMPEND SWMAN WSCAP WLDIP INTWL dd mm 1 31101 1 0 00 0 0 1 2 01 4 2 0 00 5 0 1 3 01 11 2 0 00 5 0 1 4 31 12 1 0 00 0 0 1 End of table
8. Section 3 Analytical function of Mualem Van Genuchten 1980 COFGEN1 0 01 Residual moisture content 0 0 4 cm3 cm3 R COFGEN2 0 43 Saturated moisture content 0 0 95 cm3 cm3 R COFGEN3 9 65 Saturated hydraulic conductivity 0 01 1000 cm d R COFGEN4 0 0227 Alpha main drying curve drying 0 0001 1 cm R COFGEN5 0 983 Exponent in hydraulic conductivity function 25 25 R COFGEN6 1 548 Parameter n 1 5 R COFGEN8 0 0454 Alpha main wetting curve 0 0001 1 cm R End of file KK KKK KKK KKK KKK KKK KKK KKK KK KKK RA File Sandt sol example of a file with soil hydraulic functions sections 1 3 60 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 13 Basic drainage drb SWAP allows for two different drainage routines The basic drainage routine meant for most field scale situations and the extended drainage routine meant for simulation of drainage at a regional level and surface water management If the user does not want to simulate surface water t
9. Wageningen 01 01 1980 14 00 3 0 Wageningen 01 01 1980 15 0 Wageningen 01 01 1980 17 00 Wageningen 01 01 1980 24 0 Wageningen 04 01 1980 06 00 Wageningen 04 01 1980 09 00 Wageningen 04 01 1980 10 00 Wageningen 04 01 1980 24 00 File wageniR 980 detailed rainfall data SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 129 4 5 Irrigation fixed irg Two different types of irrigation can be specified in SWAP The choice between the types depends on the economical and physical constraints of the irrigation area See Van Dam et al 1997 chapter 8 Either a fixed irrigation schedule can be specified or irrigation application can be calculated according to a number of criteria A combination of fixed and calculated irrigation is also possible An example of this would be a pre irrigation flooding the field before planting and later on irrigation based on crop development Fixed irrigation can be specified the whole year round irrigation scheduling can only be active during a cropping period Both types of irrigation may overlap but fixed irrigation has priority if irrigation is prescribed on a certain day no irrigation will be calculated for the same day This paragraph describe
10. SWOPT2 0 Switch use regional bottom flux Y 1 N 0 If SWOPT2 1 specify whether a sine or a table are used to prescribe the flux SWC2 2 Sine function 1 table 2 In case of sine function specify C2AVE 0 1 Average value of bottom flux 10 10 cm d R upwards C2AMP 0 05 Amplitude of bottom flux sine function 10 10 cm d R C2MAX 91 Daynumber with maximum bottom flux 1 366 d I In case of table specify date day month and bottom flux cm d upwards d2 m2 Qbot maximum 366 records T 0 19 5 6 0 20 JS 22 QUO End of table KK KKK KKK KK KKK KKK KK KKK KK KKK KK KKK KKK KKK KKK KK KKK ARA SWOPT3 0 Switch calculate bottom flux from deep aquifer 1 N 0 Tf SWOPT3 1 specify SHAPE 0 79 Shape factor to derive average groundwater level 0 1 R HDRAIN 110 0 mean drainage base used to correct groundw level 1 e4 0 cm R RIMLAY 500 Vertical resistance of aquitard 0 10000 d R AQAVE 140 0 Average hydraulic head in aquifer 1000 1000 cm R AQAMP 20 0 Amplitude hydraulic head sinus wave 0 1000 cm R AQTAMX 120 First daynumbe
11. CK Ck CK CK AR Section 11 Initial moisture condition SWINCO 2 Switch type of initial moisture condition 1 pressure head of each compartment is input 2 pressure head of each compartment is in hydrostatic equilibrium with initial groundwater table Tf SWINCO 1 specify initial h max 40 1 E10 1 E4 cm RJ 6 5 O 5 6 5 6 5 6 5 6 5 6 5 oO 5 oO 5 COO CD 6 5 6 5 6 5 6 5 6 5 6 5 6 5 6 5 If SWCRACK 1 specify also crit water content of each soil layer max 5 0 1 R Tf SWINCO 2 specify GWLI 75 0 Initial groundwater level 5000 100 cm R End of file KKK KK KKK KK KKK KKK KKK KKK KKK KK KKK KKK KK KKK KKK KK KKK KK RA File Hupsel swa examp
12. File wheatd crop detailed crop growth section 9 3 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 141 4 9 Detailed grass growth crp This grass crop model is a specialised form of the WOFOST crop model ignoring some of the parameters of the detailed crop model The following assumptions where made with respect to the grass cover the grass consists of the species perennial ryegrass the sward is regularly mowed and remains vegetative no grazing by cattle takes place the grassland is permanent As the grass grows continuously the crop development stage can not be used as time variable Instead the daynumber is used to define the change of variables over time It also means that the rate of development can be ignored and subsequently the parameters defining this development The grass model uses only the second growth stage which is the source assimilates limited growth stage 4 9 1 Section 1 Initial values The growth parameters needed are the initial crop weight the leaf area index and the maximum relative increase in LAI
13. Sg Oh 1 5 File hupsel swa example of a file with soil water and profile data section 1 3 54 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 11 4 Section 4 Spatial discretization SWAP allows for the definition of up to 5 soil layers Additionally the soil is subdivided in a maximum of 40 compartments which are used in the finite difference scheme Minimising the number of compartments will decrease calculation time but might increase the mass balance error For each soil layer the bottom compartment number should be defined The soil layers are numbered from top to bottom For each compartment the thickness in cm should be defined Note that for accurate calculation of top boundary fluxes the compartment thickness should be small 1 cm near the soil surface 4 11 5 Section 5 Soil hydraulic functions and maximum rooting depth Specify for each soil layer a file with soil hydraulic functions which are described in Par 4 12 Note that no file extension should be entered The depth at which rooting is limited by the soil profile should be entered here The program will also check the maximum rooting depth of the crop and will use the minimum of the two maximum depths as boundary when simulating root gro
14. Section 4 Decomposition SWDC 0 Switch consider solute decomposition Y 1 N 0 If SWDC 1 specify DECPOT 0 0 Potential decomposition rate 0 10 d R GAMPAR 0 0 Factor reduction decomposition due to temperature 0 0 5 C R RTHETA 0 3 Minimum water content for pot decomposition 0 0 4 cm3 cm3 R BEXP 0 7 Exponent in reduction decomposition due to dryness 0 2 R List the reduction of pot decomposition for each soil layer max 5 0 1 RJ FDEPTH T1 0 5 RS CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK RS Section 5 Transfer between mobile and immobile water volumes if present SWPREF 0 Switch consider mobile immobile water volumes Y 1 N 0 If SWPREF 1 specify KMOBIL 0 0 Solute transfer coef between mobile immobile parts 0 100 d R RS CK CK CK CK CK CK CK
15. Section 5 Assimilation KDIF 0 60 Extinction coefficient for diffuse visible light 0 2 R KDIR 0 75 Extinction coefficient for direct visible light 0 2 R EFF 0 45 Light use efficiency of single leaf 0 10 kg ha hr Jm2s R List max CO2 assimilation rate kg ha hr R as function of dev stage 0 2 R DVS AMAX maximum 15 records AMAXTB 0 00 40 0 1 00 40 0 2 00 20 0 End of table List reduction factor of AMAX R as function of average day temp 10 50 C R ADT TMPF maximum 15 records TMPFTB 0 00 0 01 10 00 0 60 15 00 1 00 25 00 1 00 354 00 0 00 End of table List reduction factor of AMAX R as function of minimum day temp 10 50 C R MDT TMNF maximum 15 records TMNFTB 0 00 0 00 3 00 1 00 End of table
16. Filename grass CRP Contents SWAP 2 0 Crop data of detailed grass model XX c Comment area c Te 3 o ck ck Section 1 Initial values TDWI 1000 0 Initial total crop dry weight 0 10000 kg ha R LAIEM 0 63 Leaf area index at emergence 0 10 m2 m2 R RGRLAI 0 0070 Maximum relative increase of LAI per day 0 1 m2 m2 d R CK CK CK CK
17. File hupsel hea heat flow data SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 179 4 17 Solute transport slt Input data for this option only need to be specified if the user has indicated simulation of solute transport in SWAP KEY section 5 Solute transport is simulated deterministically in SWAP by describing the physical processes The basic solute transport as used for salt transport employs the convection dispersion equation Options are provided for the user to include adsorption and decomposition of reactive solutes SWAP is focussed on the transport of salts pesticides and other solutes that can be described with relatively simple kinetics If detailed pesticide transport should be simulated SWAP can be used in combination with PESTLA Berg and Boesten 1998 If detailed nitrate transport should be simulated SWAP can be used in combination with ANIMO Groenendijk and Kroes 1998 4 17 1 Section 1 Top boundary and initial condition This section starts with the solute concentration in the precipitation In order to establish the initial conditions for the solute transport the user should specify the solute concentrations in mg cm of each compartment 4 17 2 Section 2 Diffusion dispersion and solute uptake by roots The user should specify
18. File hupsel dre extended drainage section 4c and section 4d surface water level is simulated weir characteristics as exponential function 4c or as table 4d SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 3 Section 4e automatic weir control LABEL4e 1 Do not modify For the periods when SWMAN 2 specify next two tables Table 1 IMPER index of management period 1 NMPER I DROPR maximum drop rate of surface water level 0 100 cm d positive R 5 if the value is set to zero the parameter does not play any role at all HDEPTH depth in soil profile for comparing with HCRIT 100 0 cm below soil surface R IMPER DROPR HDEPTH 2 0 0 5 st 3 0 0 0 End of table Table 2 IMPER index of management period 1 NMPER I IPHASE index per management period 1 10 I WLSMAN surface water level of phase IPHASE ALTCU 500 0 ALTCU cm R GWLCRIT groundwater leve
19. HLIM2L HLIM3H 200 C C O 6 C Section 9 Salt stress ECMAX 2 0 ECsat level at which salt stress starts 0 20 dS m R ECSLOP 0 0 Decline of rootwater uptake above ECMAX 0 40 dS m R ARA AR KC CK CC C CK CC CC Section 10 Interception COFAB 0 25 Interception coefficient Von Hoyningen Hune and Braden 0 1 cm R CA ck ck ck ck ck ck
20. RS 96 Section 4a Drainage to level 1 DRARES1 0 Drainage resistance 10 1E5 d R INFRES1 100 Infiltration resistance 0 LE5 d R SWALLO1 1 Switch for allowance drainage infiltration 1 Drainage and infiltration are both allowed 2 Drainage is not allowed 3 Infiltration is not allowed In case drainage fluxes should be distributed vertically in the saturated zone SWDIVD 1 in SWA specify the distance Ll between drainage canals 11 20 Drain spacing 1 1000 m R ZBOTDR1 90 0 Level of drainage medium bottom 1000 0 cm R SWDTYP1 2 Type of drainage medium 1 Drain tube 2 Open channel case SWDTYP1 2 Specify date day month and channel water level cm negative below field surface maximum 366 records mm LEVEL1 DU v9 0 jx GOO End of table CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK RS CK CK CK CK CK CK CK CK CK CK CK CK File Hupsel drb example of a input file with data on basic drainage section 3 4a 64 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 RS CK CK CK CK CK CK CK Section 4b Drainage to level 2 DRARES2 100 Drainage resistance 10 1E5 d R INFRES2
21. File hupsel dre extended drainage section1 characteristics of subsurface drainage systems 68 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 14 3 Section 2 surface water system This part of the module section 2 describes management and level of the surface water system The various options may have a strong impact on the way the interactions are simulated Any changes in the used option should therefore be followed by a complete go through of the input data file in order to check the consistency In order to help the user to do this the sections of the input file have been indexed and a flow chart is given in figure 6 Start section 2 ection 2a 3 Select system NSRE Section 2b urface water levels in primary water course WLP ection 2 Select control SWSEC Section 3 urface water levels in Secondary water course WLS Section 4 Miscellaneous parameters Type of water management Parameters for fixed or automatic weir Fig 6 low chart for inout data of surface water system in input file dre Section 2 contains the specification of the surface water system This section starts with a switch section 2a variable SWSRF for three modes to simulate the surface water system 1 no surface water system is simulated 2 surface water system is simula
22. File Irrig cap simulated irrigation section 1 general info 32 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 RA Section 2 Irrigation time criteria Choose one of the 5 options TCS1 1 Switch criterion Daily Stress Y 1 N 0 If TCS1 1 specify mimimum of ratio actual potential transpiration 0 1 R as function of development stage 0 2 R maximum 7 records DVS Ta Tp 0 0 0 95 2 0 0 95 End of table A X 1052 0 Switch criterion Depletion of Readily Available Water 1 N 0 If TCS2 1 specify minimal fraction of readily available water 0 1 R as function of development stage 0 2 R maximum 7 records DVS RAW OO 0 95 20 49595 End of table ox X TCS3 0 Switch criterion Depletion of Totally Available Water 1 N 0 15 7053 1 specify minimal fraction of totally available water 0 1 R as function of development stage 0 2 R maximum 7 records DVS TAW 0 0 0 50 2 0 0 50 End of table A X TCS4 0 Switch criterion Depletion Water Amount 1 N 0 If TCS4 1 spe
23. Section 2 Table of drainage 11 groundwater level relation In case drainage fluxes should be distributed vertically in the saturated zone SWDIVD 1 in SWA specify the distance L between drainage canals LM1 30 Drain spacing 1 1000 m R Specify drainage flux cm d R as function of groundwater level cm R negative below soil surface start with highest groundwater level GWL Q maximum 25 records 0 US ed 00 0 1 End of table CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK KKK RS CK CK CK CK CK File Hupsel drb example of a input file with data on basic drainage section 1 2 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 163 ADD DW CK CK CK CK CK CK KKK RS CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK Section 3 Drainage formula of Hooghoudt or Ernst IPOS 2 Position of drain 1 On top of an impervious layer in a homogeneous profile 2 Above an impervious layer in a homogeneous profile 3 At the interface of a fine upper and a coarse lower soil layer iS 4 In the lower more coarse soil layer 5 In the upper more fine soil layer Of the next parameters always specify BASEGW and KHTOP KHBOT and ZINTF in case 1205 3 4 or 5 X
24. List for each irrigation application max 50 records day month depth concentration sprinkling 0 or surface 1 application mm mg cm3 5 1 5 0 1000 0 1 End of file File hupsel irg fixed irrigation 30 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 6 Irrigation calculated cap In the previous paragraph par 4 5 a general description was given of the two options for irrigation This paragraph described the input data required for irrigation applications according to a number of criteria Scheduling irrigation can be a more optimal strategy if certain objectives need to be reached in crop production like economic returns or efficiency In order for the irrigation scheduling to be active the CAP file needs to be specified in the crop calendar file CAL 4 6 1 Section 1 General The water quality of the irrigation water and type of irrigation sprinkling or surface should be defined 4 6 2 Section 2 Irrigation time criteria Five different timing criteria can be chosen 1 Allowable daily stress This parameter determines the fraction 0 1 R of t
25. Section 7 Maintenance respiration Q10 2 0 Rel increase of respiration rate with temperature 0 5 10 C R RML 0 030 Rel maintenance respiration rate of leaves 0 1 kgCH20 kg d R RMO 0 010 Rel maintenance respiration rate of st org 0 1 kgCH20 kg d R RMR 0 015 Rel maintenance respiration rate of roots 0 1 kgCH20 kg d R RMS 0 015 Rel maintenance respiration rate of stems 0 1 kgCH20 kg d R List reduction factor of senescenc R as function of dev stage 0 2 R DVS RFSE maximum 15 records RFSETB 0 0 1 00 2 0 1 00 End of table RA C S CK C KC CK CK RA RRE Section 8 Partitioning List fraction of total dry matter increase partitioned to the roots kg kg R as function o
26. Section 1 Method SWSHF 2 Switch method iS 1 Use analytical method 2 Use numerical method DA E RS Section 2 Analytical method TAMPLI 10 0 Amplitude of annual temperature wave at soil surface 0 50 0 R TMEAN 15 0 Mean annual temperature at soil surface 5 30 C R DDAMP 50 0 Damping depth of temperature wave in soil 0 200 cm R TIMREF 90 0 Day number Jan 1 1 at top sine temperature wave 1 366 d I CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK RS CK CK CK CK CK RS CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK Section 3 Numerical method List initial temperature of each compartment max 40 10 40 C R TEMPI 6 0 5520 6 0 6 0 6 0 6 0 64 0 6 0 6 0 6 0 6 0 6 0 6 0 6 0 6 0 60 600 SN 6 0 6 0 6 0 6 20 6 0 6 0 6 0 6 0 6 0 6 0 6 0 6 0 6 0 5 6 0 6 0 64 0 539 of file
27. Section 2b Surface water level of primary system Only if SWSRF 3 then the following table must be entered Table with Water Levels in the Primary system max 52 no levels above soil surface for primary system DATE dd daynumber 1 31 1 mm monthnumber 1 12 I water level in primary water course ALTCU 1000 ALTCU 0 01 cm R WLP cm End of table Section 2c Surface water level of secondary system Tf SWSRF 2 3 then the variable SWSEC must be entered SWSEC 2 option for surface water level of secondary system 1 1 surface water level is input 2 surface water level is simulated Kk Kok Kok Kk Kok Kok Kok Kk Kok Kok KK
28. e Comment area NC C Rotation scheme Hupsel 1980 Specify for each crop maximum 3 CRPFIL Type CAPFIL EMERGENCE END crop START sch Crop data input file without CRP extension A8 Type of crop model simple 1 detailed 2 grass 3 Irrigation calculation input file with without CAP extension A8 Emergence date of the crop Forced end of crop growth Start of irrigation scheduling period CRPFIL Type CAPFIL EMERGENCE END crop START sch dl ml d2 m2 d3 m3 MaizeS 1 E 01 05 15 10 01 05 End of table File year80 cal crop rotation scheme 34 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 8 Detailed crop growth crp Depending on the availability of input date the user can choose between several crop models If the user has chosen the detailed crop model option in the crop calendar CAL then for each crop chosen by the user detailed crop growth data need to be specified for the WOFOST 6 0 model Note that although the user can choose to use ET Ref the user will need daily radiation and temperature data in order to
29. KU CK CK CK CK CK CK CK CK Section 6 Solute residence in the saturated zone SWBR Switch consider mixed reservoir of saturated zone Y 1 N 0 If SWBR specify CDRAIN solute concentration in groundwater 0 100 mg cm3 R If SWBR specify HAQUIF 5 Thickness saturated part of aquifer 0 10000 cm R POROS Porosity of aquifer 0 0 6 R KFSAT 0 Linear adsorption coefficient in aquifer 0 100 cm3 mg R DECSAT Decomposition rate in aquifer 0 10 d R CDRANI 5 Initial solute concentration in groundwater 0 100 mg cm3 R End of File File hupsel sit solute data section 3 6 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 183 JOC 11999 5 Program execution and output 5 1 Program execution The general input file Swap key must be present at the same directory as the executable SWAP All other input files should exist on the directory which has been specified in the file Swap key par 4 2 1 The output files will be written to this directory A
30. Final 71 63 cm 0 4605E 03 mg cm2 Initial 72 07 cm 0 0000E 00 mg cm2 Change 0 44 cm 0 4605E 03 mg cm2 Water balance components cm In Out Rain 66 01 Interception 4 52 Irrigation 0 50 Runoff 0 00 Bottom flux 0 00 Transpiration 26 60 Soil evaporation 14 43 Crack flux 0 00 Drainage level 1 21 39 Sum 66 51 Sum 66 95 Solute balance components mg cm2 In Out Rain O 0000E 00 Decomposition 0 0000E 00 Irrigation 0 5000E 03 Root uptake 0 0000E 00 Bottom flux 0 0000E 00 Cracks 0 0000E 00 Drainage 0 3950E 02 Sum 0 5000E 03 Sum 0 3950E 02 Output file Result inc Water balance increments cm period Date Day Rain Irrig Interc Runoff Transpiration Evaporation Drainage QBottom dd mm yyyy nr pot act pot act lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt 31 01 1980 31 4 690 0 500 0 000 0 000 0 000 0 000 0 564 0 546 3 316 0 000 29 02 1980 60 4 650 0 000 0 000 0 000 0 000 0 000 1 645 1 Del 0 000 31 03 1980 91 5 490 0 000 0 000 0 000 0 000 0 000 3 3 9 1 3 2 4 0 000 30 04 1980 121 4 060 0 000 0 000 0 000 0 000 0 000 6 376 2212103 3 049 0 000 31 05 1980 152 0 930 0 000 0 013 0 000 0 068 0 068 11 9985 AS OLY 0 220 0 000 30 06 1980 182 6 620 0 000 0 796 0 000 3 633 39 5 2 2 3 9 0 000 31 07 1980 213 14 570 0 000 1 424 0 000 VER 0 4 905 1 056 1 056 6 884 0 000 31 08 1980 24 1 640 0 000 Le UFO
31. Ck CK Section 12 Interception COFAB 0 25 Interception coefficient Von Hoyningen Hune and Braden 0 1 cm R ck ok ck ck ck ck ck Ck ck ck Ck Ck Ck Ck Ck CK ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck c oo ko ko ko ko ko ko ko ko ko ko ko ko ko ko ko ko ko Section 13 Root density distribution and root growth List relative root density 0 1 R as function of rel rooting depth 0 1 R x Rdepth Rdensity maximum 11 records RDCTB 0 0 Ta 1 0 O End of table HLIM3L 2 below which water uptake red starts at low Tpot 10000 100 cm R RDI 10 20 Initial rooting depth 0 1000 cm R RRI 1 2 Maximum daily increase in rooting depth 0 100 cm d R RDC 125 0 Maximum rooting depth crop cultivar 0 1000 cm R End of File
32. First month of the agricultural year January 1 12 2125 I Output interval ignore 0 0 366 I Switch reset output interval counter each year Y 1 N 0 Switch extra output dates are given in table Y 1 N 0 Hog wd oW W ll If SWODAT 1 table with additional output dates Date records of type dd mm yyyy max 366 1 31 1 12 1 3000 3I T 1980 1980 1980 1980 1980 1980 1980 1980 1980 1980 1980 31 1980 End of table Ne OP WWW w 00 w w WWD Ww OPPOP O File swap key with general information section 1 and 2 24 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 2 2 Section 2 Time variables Start and end of the simulation period must be specified The maximum length of the simulation period amounts 70 years A year in SWAP does not necessarily start on January 1 but rather on the first day of the month named first month of the agricultural year Note that input files with time dependent data except the meteo data files relate to an agricultural year Swap output can be
33. k k c Comment area S c Case Water and solute transport in the Hupsel area ie a catchment in the eastern part of the Netherlands xE c Example of the User s Guide reference situation 56 c A set of input data to explore SWAP RS CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK CK CK CK CK CK CK CK CK CK CK Section 1 Method DRAMET 2 Switch method of lateral drainage calculation 1 Use table of drainage flux groundwater level relation 2 Use drainage formula of Hooghoudt or Ernst 3 Use drainage infiltration resistance multi level if needed kkk ko ko
34. KK KK KK Kok Kk Kk Kok ok Kok Kk Kok kk kk kk SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 171 File hupsel dre extended drainage section 28 20 20 surface water system levels of primary and secondary water course BG XB X X gt KKK KKK KKK KKK KKK KKK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK CK CK CK CK CK Section 3 surface water level in secondary water course is input Table with Water Levels in the Secondary system max 52 DATE dd daynumber 1 31 I mm monthnumber 1 12 I WLS water level in secondary water course ALTCU 1000 ALTCU 100 cm R DATE WLS xdd mm cm End of table File hupsel dre extended drainage section 3 surface water level in secondary water course BG XB X X KG CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK CK CK CK KKK KKK KK KKK KKK KKK KKK KKK KKK KKK CK CK CK CK CK CK Section 4 surface water level is simulated
35. Section 2 Light extinction IDEV 1 Length of crop cycle 1 fixed 2 variable DIF 0 6 Extinction coefficient for diffuse visible light 0 2 R DIR 0 75 Extinction coefficient for direct visible light 0 2 R K K File maizeS crp simple crop growth sections 1 2 48 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 10 3 Sections 3 LAI or soil cover To divide potential evapotranspiration over the potential crop transpiration and potential soil evaporation the user should specify either the leaf area index LAI or the soil cover fraction SC as a function of development stage DVS 4 10 4 Section 4 Crop factor or crop height the reference evapotranspiration is input see also par 4 2 3 and 4 3 then crop factors may be used If daily meteorological data are used as input then either crop factors of crop height may be used to determine potential transpiration 4 10 5 Section 5 Rooting depth Rooting depth RD is given as a function of DVS for a maximum of 36 data pairs 4 10 6 Sect
36. SWOHR 1 option for type of discharge relationship 1 2 I 2 1 exponential relationship 5 2 table XB X X gt KKK KKK KKK KK KKK KKK KKK KKK CK CK CK CK CK CK CK CK CK CK CK KKK KKK CK CK CK CK CK CK CK CK CK CK CK CK File hupsel dre extended drainage section 4 surface water level is simulated miscellaneous and management parameters 72 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Section 4c exponential discharge relation weir characteristics If SWOHR 1 and for ALL periods specify SOFCU 0 Size of the control unit 0 1 100000 0 ha R IMPER index of management period 1 NMPER I HBWEIR weir crest levels above soil surface are allowed but simulated 0 surface water levels should remain below 100 cm above soil surface 5 the crest must be higher than the deepest channel bottom of the Secondary system ZBOTDR 1 or 2 ALTCU ZBOTDR ALTCU 100 cm R 3 If SWMAN 2 HBWEIR represents the lowest possible weir position ALPHAW alpha coefficient of discharge formula 0 1 50 0 R
37. RARA CK Section 6 Partitioning List fraction of total dry matter increase partitioned to the roots kg kg R as function of time 0 366 d R TIME FR maximum 15 records FRIB 1 0 0 30 366 0 0 30 End of table A gt List fraction of total above ground dry matter incr part to the leaves kg kg R as function of time 0 366 d R TIME FL maximum 15 records FLTB 1 0 0 60 366 0 0 60 End of table List fraction of total above ground dry matter incr part to the stems kg kg R as function of time 0 366 d R TIME FS maximum 15 records FSTB 1 0 0 40 366 0 0 40 End of table KKK KK KKK KK KKK KKK CK KKK KK KKK KKK KK KKK KK KKK KK KKK KK KKK KKK Section 7 Death rates PERDL 0 050 Maximum rel death rate of leaves due to water stress 0 3 d R List relative death rates of roots kg kg d as function of time 0 366 d R TIME RDRR maximum 15 reco
38. Hupsel In this way the boundary conditions are the same as the first year except that the bromide tracer is only applied the first year Specify the generic name for the output files for the year 1981 as Result2 c Execute a simulation d Verify results Verify leaching of bromide for 1980 and 1981 files Result bal and Result2 bal How much bromide leached to the drains on 31 December 1981 Answer Year Bromide leached Unit 1980 39 5 mg cm 1981 197 1 mg cm The bromide leaches very slowly to the ditches Although at the start of the first year 500 mg cm bromide has been applied to the field after two year only 39 5 197 1 236 6 mg cm bromide has leached to the ditches 6 2 9 2 Influence of an impervious soil layer The residence time of pesticides and nutrients in the vadose zone is very important for decomposition and uptake by roots In the saturated zone mainly dilution of solutes occurs The residence time of solutes in the saturated zone however can be considerable In the reference case par 6 1 an impermeable layer occurs at 2 m depth which results in a relatively small residence time During this second part the sensitivity of the bromide breakthrough to the impermeable layer depth will be analysed You will be using the results of the previous paragraph as reference a Change input 1 Two files need changes File Hupsel drb section 3 variable BASEGW change the depth of the impermeable layer BAS
39. array with spacing between channels drains m lower threshold daylength pre anthesis development h optimum daylength pre anthesis development h COFAB COFANI COFGEN COFQHA COFQHB COFRED COSLD CPEVA CPOND CPRE CPTRA CQBOT CQCRACK CQDRA CQDRAIN CQDRAR CQDRD CQROT CQTOP CRACKC CRACKW CRALEV CREF CREF CRUNO CVL CVO CVR CVS CWOUT CWSUPP D DAY DAY1 DAY2 DAYL DAYLP DAYNR DAYSTA DDAMP DDIF DECPOT DECSAT DECTOT DIAMPOL DIFDES DIMOCA DISNOD DistDrain DLC DLO 114 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 array with H values of C h table cm daynumber of day with no conversion potential transpiration cm actual transpiration cm array with depth of drainage base per level cm method to calculate drainage flux array with drainage resistances d array with maximum drop rate of surface water level cm d depth of the root zone cm negative current timestep d daily total gross assimilation kg ha d previous time step d maximum value of timestep allowed d minimum value of timestep allowed d AFGEN table average temp C gt daily increase temperature sum C time step modification due to solute transport d development stage at harvest array with thickness of compartments cm Ecsat level below which no salt stress occurs dS m decline root water uptake above ECMAX 40 dS m
40. average distance between water level in piezometer located in deep aquifer and ground surface cm negative when water level is below surface level angular speed water level fluctuations radians d 9 first time the water level reaches its highest position daynumber nett rain flux at short time interval cm d atmospheric evaporative demand cm d total daily shortwave radiation J m d 1 2 second Angstrom coefficient base of phreatic aquifer cm beginning of agricultural year daynumber since January 1 beginning of agricultural year yearnumber dry soil bulk density g cm 7 array with beta coefficient of weir discharge formula exponent in reduction transformation due to dryness array with compartment at the bottom of each soil layer begin of simulation daynumber calendar year begin of simulation year number initial solute concentration in aquifer mg cm cumulative actual soil evaporation cm cumulative gross irrigation depth cm cumulative gross rainfall cm crop height m AFGEN table development stage gt crop height cm array with solute concentration in immobile soil water mg cm solute concentration of irrigation water mg cm array with total concentration solved absorbed in mobile volume mg cm water storage in cracks during previous time step cm array with average solute con
41. lt Fig 2 Main structure of Swap 2 0 20 LJ SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 3 2 General data flow The main module of the model Swap consists of 7 submodels figure 3 Meteo Crop detailed non grass detailed grass and simple Soil Irrigation and Timer Sub models are divided into parts for initialisation rate calculation integration and termination The sub models perform calls to subroutines of which an overview is given in Annex B In order to facilitate tailored use of SWAP by researchers Annex C contains the main variables of the program Each submodel requires specific input In detail this will be explained in the next chapter An overview of the general data flow is given in figure 3 A summary of required input and output data is given in respectively annex E and F Apart from one general input file all files have variable file names and fixed file extensions In figure 3 the file extensions are given between brackets The general input file Swap key contains the switches that arrange the various simulation options Meteorological data can be supplied as daily data or in a separate file as short term rainfall data to allow the calculation of surface runoff Values of crop parameters enter the corresponding sub model for Crop growth which can either be a detailed mechanistic model Wofost for annual crops or grassland or a simple empirical crop model Up to three crops per year are supported in any co
42. 28 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Filename Wageni 980 Contents SWAP 2 0 Meteo data of Wageningen weather station AR Comment area CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK Station DD MM YYYY RAD Tmin Tmax HUM WIND RAIN ETref nr nr nr kJ m2 E 6 kPa m s mm mm Kock Kk Kok Kok Kk kk Kk KK KKK Kok KK a KK Kk kk IK EK Wageningen 1 1 1980 2540 eu 1 4 2 2D Care SO Wageningen 1980 9920 EO T4 5 cu Wageningen 1980 SLU 8 49 5 Wageningen 1980 740 y 66 5 Wageningen 1980 990
43. Precipitation incl irrigation water flux md Evaporation flux by interception md Actual evaporation flux by bare soil md Evaporation flux by ponding md Potential evaporation flux by soil md Potential transpiration flux md Flux of surface RUnof md GroundwAter level at end of time interval m surface Storage by ponding at soil surface at end of time interval m surface The variables h ingdra are given for the compartments 1 numnod with one exception for ing which is given for the h numnod theta numnod ingrot numnod ing numnod 1 0 gt 4 4 lt 0 0 1 0 0 4 gt 0 0 4 gt compartments 1 numnod 1 Suction pressure head of soil moisture negative when cm unsaturated Volume fraction of moisture at end of time interval m m Actual transpiration flux md Flux incoming from above compartments 1 numnod 1 md downward positive The presence of values for variables ingdra1 ingdra4 is determined by the variable nrlevs The value of nrlevs determines the ingdra 1 numnod ingdra 2 numnod ingdra 3 numnod ingdra 4 numnod JJ 0 0 4 lt 0 0 4 lt 0 0 4 lt 0 0 4 lt number of drainage systems for which flux densities must be given Flux of drainage system of 1st order canal md Flux of drainage system of 2nd order ditch md Flux of drainage system of 3rd order trench md Flux of drainage system of 4th order tube drain md 124
44. SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Salt stress Interception Root density distribution Water in soil profile swa Ponding Reduction soil evaporation Time discretization flow equation Spatial discretization Files with soil hydraulic functions Maximum rooting depth Hysteresis of soil water retention function Similar media scaling Preferential flow due to soil volumes with immobile water Preferential flow due to cracks Vertical distribution drainage flux Initial moisture condition Soil hydraulic functions sol Soil water retention function Unsaturated hydraulic conductivity function Basic drainage drb Table of drainage flux groundwater level Drainage formula of Hooghoudt or Ernst Drainage and infiltration resistances Extended drainage dre Drainage characteristics Surface water level of primary and or secondary system Simulation of surface water level Weir characteristics Bottom boundary conditions bbc Heat flow hea Analytical or numerical method Solute transport slt Top boundary and initial condition Diffusion and dispersion Solute uptake by roots Adsorption Decomposition Transfer between mobile and immobile water volumes Residence in saturated zone SC DLO TECHNICAL DOCUMENT 53 DOC 11999 5 Annex E Summary of input data General information Swap key Environment Time variables Meteorological data In and output files for the sub runs Processes w
45. Section 1 drainage characteristics RSRO 0 5 drainage Resistance of Surface RunOff 0 001 1 0 d R NRSRF 2 number of subsurface drainage levels 1 5 1 Table with physical characteristics of each subsurface drainage level LEVEL drainage level number 1 NRSRF I SWDTYP type of drainage medium open 0 closed 1 e TY spacing between channels drains 1 1000 m R ZBOTDR altitude of bottom of channel or drain ALTCU 1000 ALTCU 0 01 cm R GWLINF groundw level for max infiltr 1000 0 cm rel to soil surf R RDRAIN drainage resistance 1 100000 d R RINFI infiltration resistance 1 100000 d R x Variables RENTRY REXIT WIDTHR and TALUDR must have realistic values when the type of drainage medium is open second column of this table SWDTYP 0 For closed pipe drains SWDTYP 1 dummy values may be entered RENTRY entry resistance 0 10 d R REXIT exit resistance Oras Os a R WIDTHR bottom width of channel 0 100 cm R TALUDR side slope dh dw of channel 0 01 5 R LEV SWDTYP L ZBOTDR GWLINF RDRAIN RINFI RENTRY REXIT WIDTHR TALUDR 1 0 250 0 1093 0 350 0 150 0 4000 0 0 8 0 8 100 0 1 5 2 0 200 0 1150 0 300 0 150 0 1500 0 0 8 Gado 1000 145 End of table
46. light use efficiency single leaf kg ha h m s entrance resistance of the drain tube d path to project data directory end of simulation run daynumber calendar year end of simulation run yearnumber potential evaporation rate from a bare soil mm d potential transpiration rate from a dry crop mm d potential transpiration rate from a wet crop mm d switch indicating 11 flow through cracks has to be considered array with reduction factor of potential transformation rate for each layer total instantaneous gross assimilation rate kg ha h switch indicating presence of a crop array describing how hydraulic properties of each soil layer are specified VanGenuchten parameters or with a table flag indicating last timestep of a day flag indicating timestep correction due to detailed rainfall data flag indicating how actual soil evaporation is obtained AFGEN table development stage gt fraction of total above ground dry matter increase partitioned to the leaves flag indicating profile is totally saturated array with drainage infiltration flux per drainage level cm d DMCH DNOCON DPTRA DQROT DRAINL DRAMET DRARES DROPR DRZ DT DTGA DTMI DTMAX DTMIN DTSMTB DTSOLU DVSEND DZ E ECMAX ECSLOP EFF ENTRES ENVSTR ERUND ERUNY ESO ETO EWO F FCRACK FDEPTH FGROS FLCROP FLGENU FLLAST FLRAIC FLREVA FLTB FLTSAT FluxDr
47. rare 5 Wageningen 1980 1090 5 2 OS Wageningen Wageningen Wageningen Wageningen Wageningen Wageningen Wageningen Wageningen Wageningen Wageningen Wageningen 450 J0U 00 00 00 rn 00 00 100 Hs O1 N 00 A ANN A 00 1000 0 C 300 COESO 0 P n N ww 00 r2000 I2 OO OS OOO 62 10 c0 BRO Ul XO XO XO LO XO XO XO LO LO LO dO File Wageni 980 daily meteorological data RS CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK Filename Wagenir 980 Contents SWAP 2 0 detailed rainfall data of weather station Station DD MM YYYY HR MN Rain Units nr nr DI nr mm
48. 0 100 C R ADT DTSM maximum 15 records DTSMTB 0 0 00 30 00 30 00 45 00 30 00 End of table DVSEND 2 00 development stage at harvest 0 3 0 R Section 3 Initial values TDWI 210 0 Initial total crop dry weight 0 10000 kg ha R LAIEM 0 1370 Leaf area index at emergence 0 10 m2 m2 R RGRLAI 0 0070 Maximum relative increase of LAI per day 0 1 m2 m2 d R
49. CC Section 9 Death rates PERDL 0 030 Maximum rel death rate of leaves due to water stress 0 3 d R List relative death rates of roots kg kg d as function of dev stage 0 2 R DVS RDRR maximum 15 records RDRRTB 0 00 0 00 0 0 00 1 5001 0 02 2 00 0 02 End of table List relative death rates of stems kg kg d as function of dev stage 0 2 R DVS RDRS maximum 15 records RDRSTB 0 00 0 00 Te DO 0 00 1 5001 0 02 2 00 0 02 End of table Ck CK KK KKK KKK KKK KK KKK KK KKK KK KKK KKK KK KKK KK KKK KKK KKK KKK KK KKK KK KKK KKK KKK KK KK KKK KKK RA Ck CK KKK KK KKK KKK KK KKK KK KEK KKK KKK KKK KK KKK KK KKK KK KKK KK KKK KK KEK KKK KKK KK KKK KKK KK o Section 10 Crop water use HLIM1 10 0 No water extraction at higher pressure heads 100 100 cm R HLIM2U 25 0 h below which optimum water extr starts for top layer 1000 100 cm R HLIM2L 25 0 h below which optimum water extr starts for sub layer 1000 100 cm R HLIM3H 320 0 h below which water uptake red starts at high Tpot 10000 100 cm R O h HLIM4 8000 0 No water extraction at lower pressure heads 16000 100 cm R RSC 70 0 Minimum cano
50. KVTOP and KVBOT in case IPOS 4 or 5 GEOFAC in case IPOS 5 BASEGW 2 Level of impervious layer 1E4 0 cm 2 neg below soil surf KHTOP 25 0 Horizontal hydraulic conductivity top layer 0 1000 cm d KHBOT 10 0 horizontal hydraulic conductivity bottom layer 0 1000 cm d KVTOP 5 0 Vertical hydraulic conductivity top layer 0 1000 cm d KVBOT 10 9 Vertical hydraulic conductivity bottom layer 0 1000 cm d GEOFAC 4 8 Geometry factor of Ernst 5 55500 ZINTF 150 Level of interface of fine and coarse soil layer 1E4 0 cm Always specify LM2 11 Drain spacing 1 1000 m R WETPER 30 0 Wet perimeter of the drain 0 1000 cm R ZBOTDR 80 0 Level of drain bottom 1000 0 cm R neg below soil surface ENTRES 20 0 Drain entry resistance 0 1000 d R DA RS Section 4 Drainage and infiltration resistance NRLEVS 2 Number of drainage levels 1 5 I
51. Y 11 00 9 2 00 Impermeable Boulder clay Y Fig 7 The schematisation of the Hupsel reference case Table 3 Maize crop data for the reference situation in the Hupsel catchment Development Stage 0 0 0 3 0 5 0 7 1 0 1 4 2 0 Leaf Area Index 0 05 0 14 0 61 4 1 5 0 5 8 5 2 Soil Cover 0 05 0 2 0 5 1 0 1 0 Crop Height cm 1 15 40 140 170 180 175 Rooting depth cm 5 20 50 80 90 100 88 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 6 1 2 Solute On 5 January 5 mm KBr is applied with a concentration of 1000 mg cm The dispersion length equals 5 cm Molecular diffusion is neglected as it is much smaller than mechanical dispersion at the prevailing soil water fluxes In case of bromide adsorption and decomposition are zero which makes bromide very suitable for tracer studies 6 1 3 Heat Heat transport is numerically simulated using the measured daily air temperature as top boundary condition and zero flux as bottom boundary condition 6 1 4 Output of reference situation The simulation period lasts from 1 January to 31 December 1980 The simulated water and solute balance are printed at the end of each month The monthly output includes the simulated soil profile data on water content pressure head solute concentration and soil temperatures The following output files are generated and listed in annex A Result wba Water balance with cumulative data Result inc Water balanc
52. BETAW beta coefficient of discharge formula 0 5 3 0 R IMPER HBWEIR ALPHAW BETAW 1 1114 0 30 1 5 2 1110 0 350 1 4765 3 117040 59 1 4765 4 1114 0 3 0 1 4765 End of table 96 CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK 9 9 9 CK 9 9 KU KK 9 9 9 KK KU 9 KG KG BG X X X Section 4d table discharge relation LABEL4d 1 Do not modify If SWOHR 2 and for ALL periods specify IMPER index of management period 1 NMPER I ITAB index per management period 1 10 I HTAB surface water level ALTCU 1000 ALTCU 100 cm R first value for each period ALTCU 100 cm QTAB discharge 0 500 cm d R should go down to a value of zero at a level that is higher than the deepest channel bottom of secondary surface water system A A A X F F TMPER ITAB HTAB OTAB End of table
53. Goto Drainage basic Load file Hupsel drb Change the horizontal hydraulic conductivity of the top layer from 25 to 2 5 cm d c Execute a simulation d Verify results Verify runoff transpiration drainage and groundwater levels at 31 March 31 July and 30 September for the simulations with the sand and the clay soil Answer Fluxes Sand Clay Unit Runoff 0 0 12 6 cm year Potential transpiration 29 6 29 6 cm year Actual transpiration 26 6 22 5 cm year Drainage 21 4 11 9 cm year Groundwaterlevels Sand Clay Unit 31 March 70 0 29 2 cm 31 July 78 5 65 6 cm 30 September 131 5 162 1 cm Although daily values for precipitation are used runoff occurs at the clay soil The higher groundwater levels in the clay soil during the growing season cause less root water uptake at the deeper soil layers and thus less actual transpiration In the second half of the year the groundwater levels decline because less water percolates to the groundwater SC DLO TECHNICAL DOCUMENT 53 DOC 11999 5 6 2 6 Hysteresis of retention function During this exercise you will include hysteresis of the retention function and check its effect on the soil water balance a Initialise with reference situation described in par 6 1 execute INITIAL BAT b Change input 1 Choose the hysteresis option by changing in the soil water file Hupsel swa section 6 the variable SWHYST As we start the simulation in a wet period during winter we should start from the ma
54. O EDS C SO DUO CY 2C VC Lp 144E 183E 232E 289E 348E 429E 412E 274E 130E 494E 01 148E 01 353E 2T03E SLIGE 129E 7728 0002 0002 0002 NNNNDNDNDNDNRRRP O O Or OQ OO OD O c O 109E 0 974E 860E 745E 630E 516E 401E 287E SIV2E SE 56 206 66 201 76 198 86 195 96 193 106 191 116 190 C C5 C C 6 6 O CO C Cy C3 C C OO Oi OO C OO 0 00 OO DIO O 26 CS C C9 C XC XC 0 cC C O A CX uu Ot 2 c0 C O 10 00 00 O O Ot O OD OO CY SCC O 10 10 00 CO CO CX CO CX CO 2 2 CO CD CO CO C CO CX CX CX CX O D O CO CO CO CO CO ds do 5 do do do ds ds HHP PH ds 4s YN VDA AD AD 1 01 41 44 C GG C CX CX 6 OO C3 C OC CN FOO 6 0 O C CY OO Gi 0 Cy C O OOo CCo 0O0OOO OO OOO LD 62 62 62 62 62 62 62 62 62 6 62 62 6 ODO DOO OD OO ta OOOO O OO O OO OO OOO 6 62 6 HO 6 6 60 62 6 6 6 OO OO Cd Q CD C9 00 00 CD OO 6 0 O 0 CO OO CO CD CD CD CO 62 62 CO CO CO DO CO COD D pes bp Es Es pa N N N OO O 0 0 CO O C 65 65 65 6 0 01 01 OF U1 OT O1 Ui gi 0 OT 01 01 O01 OT 01 OT 01 O O 6 6 6 CO 0 0 0 0 0 00 OO DO C2 0 0 0 O 0 O 00 OO CO CO O O OD WWWW C
55. Soil and Irrigation Chapter 6 describes an application and contains exercises to explain program use The application refers to water and solute transport on a maize field in the Hupsel catchment Exercises indicate the effect of different meteorological years irrigation different crops soil texture hysteresis of the retention function scaling of the soil hydraulic functions and different root density distributions Also the effect of errors in soil profile description and of preferential flow on bromide leaching to surface water is shown The final exercise applies to drainage design In the annexes the SWAP subroutines and the main program variables are listed SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 19 gt 11999 1 Introduction Knowledge of water flow and solute transport processes in the vadose zone is essential to derive proper management conditions for plant growth and environmental protection in agricultural and environmental systems Numerical models are widely used as helpful tools to gain insight in the processes occurring in these complex systems and to analyse optional management scenarios One of these numerical models is SWAP Soil Water Atmosphere Plant the successor of the agrohydrological model SWATR Feddes et al 1978 and some of its numerous derivatives The experiences gained with the existing SWATR versions were combined into SWAP which integrates water flow solute transport and crop growth according to cur
56. canopy that intercepts precipitation transpires and shades the ground To facilitate the user in making choices when applying simple crop growth a flowchart is given in figure 4 The development stage of the crop can be either controlled by the temperature sum or can be linear in time section 1 Instead of leaf area index soil cover fraction may be used to divide potential evapotranspiration into potential transpiration and potential evaporation section 3 Aerodynamic properties section 4 are used to calculate potential transpiration If the reference evapotranspiration is input see also par 4 2 3 and 4 3 then crop factors may be used If daily meteorological data are used as input then either crop factors of crop height may be used to determine potential transpiration Etar a IDEY Emp IDEV 2 ayp edion 11 ru ME T ot rop oole moerature surn ght Extinction ardor 2 am 7 1 7 ia 2 P pr Bak sires Data on Sal Stress section 3 Interception section M nox dansrty distribution senor 117 1 End Fig 4 Flow chart for input data on simple crop growth SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 147 4 10 1 Section 1 Crop development Crop development can be either modelled linearly fixed length of the crop cycle or can be controlled by the temperature sum variable length of the crop cycle In the case of a fixed crop cycle only the toal length of the crop cycle
57. e the dispersion length D v for which Jury et al 1991 indicated a value between 0 5 and 2 cm in case of packed laboratory columns and a value between 5 and 20 cm for field conditions e the molecular diffusion coefficient in the order of 0 012 cm day which is generally much smaller than the dispersion coefficient and in most field conditions can be neglected e the solute uptake factor K for the roots if K gt 1 solutes are taken up at a higher rate than would follow from soil water uptake rate by roots times the solute concentration 4 17 3 Section 3 Adsorption If the user wants to consider solute adsorption implying delay of solute breakthrough because part of the solute is adsorbed to the soil particles the user should supply the following parameters e Freundlich coefficient in case of linear adsorption this parameter is equal to the slope of the adsorption desorption curve e Freundlich exponent this parameter determines whether the adsorption is non linear In case of linear adsorption the user should specify a value of 1 e reference value of the solute concentration which is used to make the Freundlich exponent dimensionless 4 17 4 Section 4 Decomposition Solute decomposition is calculated from a potential solute decomposition rate which applies to soil from the plow layer at 20 C and at a suction h 100 cm The potential decomposition rate is reduced under the influence of temperature soil water conten
58. notably the SWA file soil water flow data the SLT file solute transport data and the HEA file heat flow data The variable Path indicates the directory where the user wants to store the input and output files An example is ciSwaplexamplel or example If no characters Path are given then the program will assume that all input files are located at the current directory the directory from which the model is executed Output files will also be written to the directory specified with the variable Path XM KKK KKK KKK KKK KKK KKK KK KK KK KK KKK KKK KKK KK KKK KKK KKK KKK KKK KKK Filename SWAP KEY Contents SWAP 2 0 General input data AAA KK KKK KKK KKK KKK KKK KKK KK KK KK KK KK KKK KK KK KK KKK KKK KK KKK KKK KKK KKK KK Comment area C Case Water and solute transport in the Hupsel area XG a catchment in the eastern part of the Netherlands TO C Example of the User s Guide reference situation EC C A set of input data to explore SWAP
59. 0 000 9516 9 062 0 757 0 757 0 006 0 000 30 09 1980 274 2 740 0 000 0 829 0 000 7065 OS 0 484 0 484 0 000 0 000 31 10 1980 305 6 740 0 000 0 383 0 000 14991 1499 1 180 1 152 0 000 0 000 30 11 1980 335 5 260 0 000 0 000 0 000 0 000 0 000 1 274 1 192 0 000 0 000 31 12 1980 366 5 620 0 000 0 000 0 000 0 000 0 000 0 720 0 678 05053 0 000 SC DLO TECHNICAL DOCUMENT 53 DOC 11999 5 Output file Result wba DATE DAY RAIN cm IRR cm RUO TRA cm EVS cm FLUX cm DSTOR GWL ODIF Date dd mm yyyy nr gr net gro net cm Pot ues act Dot act La bars bot cm cm cm dd mm yyyy lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt 31 01 1980 31 4 69 4 69 0 5 0 5 0 00 0 00 0 00 0 56 0 55 34 32 0 00 1 3 3 73 1 0 00 0 29 02 1980 60 9 34 9 34 0 5 0 5 0 00 0 00 0 00 Dae DA LO 8 45 0 00 0 31 76 8 0 00 29 02 1980 31 03 1980 91 14 83 14 83 0 5 0 5 0 00 0 00 0 00 5 53 3 54 10 82 0 00 0 97 7
60. 0 5000E 03 0 0000E 00 0 0000E 00 0 4992E 03 0 0000E 00 0 0000E 00 0 7961E 00 0 0000E 00 0 0000E 00 0 0000E 00 0 2 30 4 1980 121 0 5000E 03 0 0000E 00 0 0000E 00 0 4970E 03 0 0000E 00 0 0000E 00 0 2961E 01 0 0000E 00 0 0000E 00 0 0000E 00 0 2 31 5 1980 152 0 5000E 03 0 0000E 00 0 0000E 00 0 4969E 03 0 0000E 00 0 0000E 00 0 3075E 01 0 0000E 00 0 0000E 00 0 0000E 00 0 2 30 6 1980 182 0 5000E 03 0 0000E 00 0 0000E 00 0 4966E 03 0 0000E 00 0 0000E 00 0 3356E 01 0 0000E 00 0 0000E 00 0 0000E 00 0 2 31 7 1980 213 0 5000E 03 0 0000E 00 0 0000E 00 0 4607E 03 0 0000E 00 0 0000E 00 0 3929E 02 0 0000E 00 0 0000E 00 0 0000E 00 0 2 31 8 1980 244 0 5000E 03 0 0000E 00 0 0000E 00 0 4607E 03 0 0000E 00 0 0000E 00 0 3931E 02 0 0000E 00 0 0000E 00 0 0000E 00 0 2 30 9 1980 274 0 5000E 03 0 0000E 00 0 0000E 00 0 4607E 03 0 0000E 00 0 0000E 00 0 3931E 02 0 0000E 00 0 0000E 00 0 0000E 00 0 2 31 10 1980 305 0 5000E 03 0 0000E 00 0 0000E 00 0 4607E 03 0 0000E 00 0 0000E 00 0 3931E 02 0 0000E 00 0 0000E 00 0 0000E 00 0 2 30 11 1980 335 0 5000E 03 0 0000E 00 0 0000E 00 0 4607E 03 0 0000E 00 0 0000E 00 0 3931E 02 0 0000E 00 0 0000E 00 0 0000E 00 0 2 31 12 1980 366 0 5000E 03 0 0000E 00 0 0000E 00 0 4605E 03 0 0000E 00 0 0000E 00 0 3950E 02 0 0000E 00 0 0000E 00 0 0000E 00 0 48E 02 Output file Result cr1 DATE ID DVS LAI CH RD CRT RELY dd mm yyyy nr cm cm i k lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt 31 05 1980 1
61. 100 IntrxltratioH resistance DOLES dyo RI SWALLO2 1 Switch for allowance drainage infiltration 1 Drainage and infiltration are both allowed 2 Drainage is not allowed 3 Infiltration is not allowed In case drainage fluxes should be distributed vertically in the saturated zone SWDIVD 1 in SWA specify the distance L2 between drainage canals L2 20 Drain spacing 1 1000 m R ZBOTDR2 90 0 Level of drainage medium bottom 1000 0 cm R SWDTYP2 2 Type of drainage medium 1 Drain tube 2 Open channel In case SWDTYP2 2 specify date day month and channel water level cm negative if below field surface maximum 366 records dd mm LEVEL2 01 01 90 0 31 12 90 0 End of table RS CK RS CK CK CK CK CK CK CK CK Section 4c Drainage to level 3 DRARES3 100 Drainage resistance 10 1E5 d R INFRES3 100 Infiltration resistance O lE5 d Rj SWALLO3 1 Switch for allowance drainage infiltration 1 Drainage and infiltration are both allowed 2 Drainage is not allowed 3 Infiltration is not allowed In case drainage fluxes should be distributed vertically in the saturated zone SWDIVD 1 in SWA specify the distance L3 between drainage canals
62. 90 0 31 12 90 0 End of table End of file KKK KKK Ck CK CK CK CK CK CK CK CK KKK KKK KKK KKK KKK KKK KKK KKK KKK CA File Hupsel drb example of a input file with data on basic drainage section 4d 4e 66 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 14 Extended Drainage dre 4 14 1 General This paragraph describes data requirements for applying the model to situations with extended drainage The term extended means that the surface water levels are not prescribed independently but are simulated as a result of the soil water balance and surface water management The groundwater surface water system is schematised at the scale of a horizontal subregion Only a single representative groundwater level is simulated which is stretched over a scale that in reality involves a variety of groundwater levels Most of the theory has been described by Van Dam et al 1997 chapter 9 some additional remarks are given in this paragraph The input data for extended drainage are given in the input file with the extension DRE This file is divided into 2 sections e section 1 drainage characteristics e section 2 surface water system Ahead of these sections the user should specify the altitude of the control unit soil surface with respect to a certain reference level ALTCU Water management levels are given with respect to the same reference Of
63. CK CK CK CK CK CK CK CK CK KKK CK CK CK Comment area Case Water and solute transport in the Hupsel area a catchment in the eastern part of the Netherlands c Example of the User s Guide reference situation c A set of input data to explore SWAP RS CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK Section 1 Ponding PONDMX 0 2 Maximum thickness of ponding water layer 0 1000 cm R CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK RS CK CK Section 2 Soil evaporation SWCFBS 0 Switch for use of coefficient CFBS for soil evaporation 1 N 0 0 CFBS is not used 1 CFBS used to c
64. FluxDrComp array with flux per node to from each drainage level cm d array with corresponding mobile fractions array with corresponding mobile fractions array with volume fraction of mobile region in a compartment AFGEN table development stage gt fraction of total above ground dry matter increase partitioned to the storage organs SC DLO TECHNICAL DOCUMENT 53 DOC 11999 5 FMI FM2 FMOBIL FOTB FREXP Freundlich adsorption exponent FRTB AFGEN table development stage gt fraction of total dry matter increase partitioned to the roots FSTB AFGEN table development stage gt fraction of total above ground dry matter increase partitioned to the stems FTOPH flag indicating head T or flux F controlled top boundary condition G GAMPAR transformation reduction factor due to temperature C GEOFAC geometry factor Ernst GEOMF geometry factor 3 isotropic shrink GIRD gross irrigation rate cm d GRAI gross daily rainfall rate cm d GWL groundwater level cm negative below surface level GWLBAK array with last four groundwater levels cm GWLCRIT array with maximum value for GWL of phase IPHASE cm GWLEV groundwater level cm below surface is negative GWLI initial groundwater level cm below surface level GWLINF array with groundwater level for maximum infiltration cm neg GWLTAB A
65. KKK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK CK CK CK CK Section 6 Optional output files each run generates a separate file SWVAP 1 Switch output profiles of moisture solute and temperature Y 1 N 0 SWDRF 0 Switch output drainage fluxes only for extended drainage Y 1 N 0 SWSWB 0 Switch output surface water reservoir only for ext dr 1 N 0 AAA RA Section 7 Optional output files for water quality models or specific use
66. No water extraction at lower pressure heads 16000 100 cm R RSC 70 0 Minimum canopy resistance 0 1000 s m R ADCRH 0 5 Level of high atmospheric demand 0 5 cm d R ADCRL 0 1 Level of low atmospheric demand 0 5 60 8 R RA RA Section 8 salt stress ECMAX 2 0 ECsat level at which salt stress starts 0 20 dS m R ECSLOP 0 0 Decline of rootwater uptake above ECMAX 0 40 dS m R Ck CK KK KKK KKK KKK KKK KK KK KKK KK KKK KK KKK KKK KKK KKK KK KKK KKK KK KKK KKK KK KKK KK KKK KK KKK Ck CK KKK KK KK KKK KKK KK KKK KKK KK KKK KKK KK KKK KKK KKK KKK KKK KK KK KKK KKK KK KKK KK KKK KKK KKK koX Section 9 interception COFAB 0 25 Interception coefficient Von Hoyningen Hune and Braden 0 1 cm R
67. Phone 31 317 474200 fax 31 317 424812 e mail postkamer sc dlo nl Wageningen Agricultural University P O Box 9101 NL 6700 HB Wageningen The Netherlands Phone 31 317489111 fax 31 317484449 e mail office alg vl wau nl No part of this publication may be reproduced or published in any form or by any means or stored in a data base or retrieval system without the written permission of the DLO Winand Staring Centre The DLO Winand Staring Centre assumes no liability for any losses resulting from the use of this document Projectnumber 81094 Technical Document 53 IS 03 99 Contents Summary Introduction 2 Brief theoretical description oystem definition ooil water flow ooil heat flow Solute transport Crop growth Soil heterogeneity Irrigation and drainage ourface water system Sensitivity and limitations Technical model description Model structure General data flow Model extensions 3 1 3 2 3 3 Program inputs Introduction General information Swap key 4 2 1 Section 1 Environment 4 2 2 Section 2 Time variables 4 2 3 Section 3 Meteorological data 4 2 4 Section 4 In and output files for the simulation runs 4 2 5 Section 5 Processes which should be considered 4 2 6 Section 6 Optional output files 4 2 7 Section 7 Optional output files for water quality models Daily meteo data station yyy Detailed rainfall stationR yyy Irrigation fixed irg Irrigation calculated ca
68. Roelsma 1998 The model SWAP simulates the residence time of solutes in the saturated zone analogous to mixed reservoirs In this way solute transport from soil surface to surface water can be derived 2 5 Crop growth Crop growth can be simulated by the code WOFOST 6 0 Hijmans et al 1994 The cropping pattern may consist of maximal three crops per agricultural year WOFOST calculates the radiation energy absorbed by the canopy as function of incoming radiation and crop leaf area Using the absorbed radiation and taking into account photosynthetic leaf characteristics the potential gross photosynthesis is calculated The latter is reduced due to water and or salinity stress as quantified by the relative transpiration and yields the actual gross photosynthesis Part of the carbohydrates CH2O produced are used to provide energy for the maintenance of the existing live biomass maintenance respiration The remaining carbohydrates are converted into structural matter In this conversion some of the weight is lost as growth respiration The dry matter produced is partitioned among roots leaves stems and storage organs using partitioning factors that are a function of the crop phenological development stage The fraction partitioned to the leaves determines leaf area development and hence the dynamics of light interception The dry weights of the plant organs are obtained by integrating their growth rates over time During the development of
69. Therefore we start with an inialisation by running the batch file INITIAL BAT This batch file copies the input files of SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 89 the reference situation from directory EXAMPLES EXERCISE INITIAL to the directory EXAMPLES EXERCISE Each exercise consists of four steps a Initialise with reference situation described in par 6 1 execute INITIAL BAT b Change input data in input files and save changed input files c Execute a simulation with SWAP execute SWAP BAT 0 Verify results The input can be changed in two ways 1 using a text editor directly editing the input files 2 using the graphical user interface Additional input files required for some of the exercises are located on the directory EXAMPLES EXERCISE 6 2 1 Meteorological year In the first exercise we evaluate the effect of a different meteorological year a Initialise with the reference situation described in par 6 1 execute INITIAL BAT b Change input 1 Select the relatively wet year 1981 by the following changes in the file Swap key section 2 the simulation period must be changed to the period 1 January 1981 until 31 December 1981 the output dates must be changed accordingly note that February has 28 days in 1981 2 Goto Key Load SwapGui key on directory c swap examples exercise The following changes in section Timing have to be carried out the simulation period must be changed to the peri
70. a low minimum temperature at night when the assimilates are transformed In case of a grass crop the maximum CO2 assimilation rate AMAX is a function of the daynumber The user can enter data up to 15 data pairs to characterise this relationship The reduction factor TMPF based on average daily temperature accounts for sub optimum temperatures The input allows for a relationship between TMPF and daynumber defined in up to 15 data pairs The influence of a low minimum night temperature on the reduction factor of AMAX TMNF also can be defined by a relationship of up to 15 data pairs 4 9 4 Section 4 Conversion of assimilates into biomass Conversion into dry matter in case of a grass ignores storage organs The assimilates are transformed into structural biomass after subtraction of respiration for maintenance Depending on the product formed the efficiency of the conversion of primary photosynthates to structural plant material varies Efficiencies are crop specific and should be specified in this section 4 9 5 Section 5 Maintenance respiration An increase in temperature causes an increase in maintenance respiration Generally a 10 C temperature increase causes maintenance respiration to increase by a factor 2 Respiration depends on relative maintenance coefficients of the specific crop organs These coefficients are proportional to the dry weights of the plant organs senescence will decrease respiration In case of a gras
71. are available or the maximum rooting depth is reached 44 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Section 2 Green surface area List specific leaf area ha kg R as function of time 0 366 d R i TIME SLA maximum 15 records SLATB 1 0 0 0015 80 0 0 0015 300 0 0 0020 366 0 0 0020 End of table SSA 0 0 Specific stem area 0 1 ha kg R SPAN 30 0 Life span of leaves at optimum conditions 0 366 d R TBASE 0 0 Lower threshold temperature for ageing of leaves 10 30 C R Dag ck ko ko ko ko ko ko ko ko ko ko ko Section 3 Assimilation KDIF 1 00 Extinction coefficient for diffuse visible light 0 2 R KDIR 0 75 Extinction coefficient for direct visible light 0 2 R EFF 0 50 Light use ef
72. boundary conditions and with known relations between 0 and K These relationships which are generally called the soil hydraulic functions can be measured directly in the soil or might be obtained from basic soil data The Richards equation is solved using an implicit finite difference scheme as described by Belmans et al 1983 This scheme has been adapted such that the solution applies both to the unsaturated and saturated zone that water balance errors due to non linearity of the differential water capacity are minimised and that calculated soil water fluxes at the soil surface are more accurate Phreatic or perched groundwater levels are found at the transition from negative to positive soil water pressure heads Important features of the Richards equation are that it allows the use of soil hydraulic data bases and simulation of all kinds of management scenarios The soil hydraulic functions are described by analytical expressions of Van Genuchten 1980 and Mualem 1976 or by tabular values Hysteresis of the water retention function can be taken into account with the scaling model of Scott et al 1983 Root water extraction at various depths in the root zone is calculated from potential transpiration root length density and possible reductions due to wet dry or saline conditions 2 3 Soil heat flow ooil temperature may affect the surface energy balance soil hydraulic properties decomposition rate of solutes and growth rate of roo
73. ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck o ko ko ko ko ko ko ko ko ko ko ko ko ko ko Section 11 Root density distribution and root growth List relative root density 0 1 R as function of rel rooting depth 0 1 RJ E Rdepth Rdensity maximum 11 records RDCTB 0 0 1 0 1 0 1 40 End of table RDI 50 0 Initial rooting depth 0 1000 cm R RRI 0 0 Maximum daily increase in rooting depth 0 100 cm d R RDC 50 0 Maximum rooting depth crop cultivar 0 1000 cm R file KK KKK KKK KKK KK KK KKK KKK KKK KKK KK KKK KK KKK KKK KK KKK KK File grass crp detailed grass growth section 6 11 46 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 10 Simple crop growth crp The simple crop model is useful when crop growth does not need to be simulated or when crop growth input data are insufficient The simple crop growth model represents a green
74. in the upper part of the groundwater and describes the interaction with regional groundwater Integrated modelling of the Soil Water Atmosphere Plant system Atmosphere Surface waters zone Saturated i3 drainages one subsurface imac Deep Groundwater Fig 1 A schematised overview of the modelled system 2 2 Soil water flow Spatial differences of the soil water potential cause flow of soil water Darcy s equation is used to quantify these soil water fluxes For one dimensional vertical flow Darcy s equation can be written as SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 113 9 h 2 q K h 7 1 2 where qis soil water flux density positive upward cm d Kis hydraulic conductivity cm 1 his soil water pressure head cm and zis the vertical co ordinate cm taken positively upward Water balance considerations of an infinitely small soil volume result in the continuity equation for soil water 00 dg PR 2 where 0 is volumetric water content cm cm tis time d and S is soil water extraction rate by plant roots cm cm d Combination of Eq 1 and 2 results in the well known Richards equation 3 Kh 2 02 0 oh P ra S h 3 where C is the water capacity d8 dh cm Richards equation has a clear physical basis at a scale where the soil can be considered as a continuum of soil air and water SWAP solves Eq 3 numerically subject to specified initial and
75. is given below for a situation with 2 levels of drainage Filename Hupsel DRE Contents SWAP 2 0 extended drainage routine 42 example for interaction with surface water system CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK c Comment area XG c OMV calibration runs EG AAA Kk ALTCU 1200 0 ALTitude of the Control Unit relative to reference level AltCu 0 0 means reference level coincides with surface Level 300000 300000 em R BG BG XB X X KG KG KKK CK CK CK CK CK CK CK
76. maximum sub irrigation rate Navg cm drainage resistance for situations with drainage Yarain d drainage resistance for situations with infiltration Ying d entrance resistance for situations with drainage only for channels Yen d entrance resistance for situations with infiltration only for channels Yexit d depth of channel bed depth of drains Zbeai cm negative Side slope of channels only for channels dz dWgrain Sarain 7 In addition to the explanation given in chapter 9 of Van Dam et al 1997 it should be noted that for this quasi subregional approach the entrance resistance is included in the SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 67 expression for the total drainage resistance Yor in the following manner iita ll drain Y tot T drain T entr 5 where Ugrain Is the wetted perimeter cm and Yent is the entrance resistance d as given by Ernst 1956 In the case of channels the wetted perimeter is computed for each time step from the surface water level Ns the channel bed level 206 the channel bed width Wyrain and the channel side slope Sarain In the case of pipe drains however entrance exit resistance is not calculated from the wetted perimeter and therefore should be included in the drainage sub irrigation resistance If a parameter is not relevant e g width of channel bed for drains a dummy like 0 should be entered The content of Section 1
77. of each soil compartment max 40 0 500 cm R DZ 1 0 1 0 1 40 1 0 1 0 1 0 1 0 1 0 1 0 160 5 0 5530 54 0 5 0 5 0 5 0 5 0 540 530 5350 10 0 10 0 10 0 10 0 10 0 10 0 10 0 10 0 10 0 10 0 10 0 10 0 10 0 10 0 ck ck ck ck ck gt ck ck ck ck gt ck ck ck gt ee ck Section 5 5011 hydraulic functions and maximum rooting depth Specify for each soil layer max 5 the hydr function file without SOL ext A8 SOLFIL Sandt Sands Specify for each soil layer max 5 the soil texture g g mineral parts the organic matter content g g dry soil 5 PSAND PSILT PCLAY ORGMAT 0 80 0 15 0 05 0 100 0 78 0 14 0 08 0 012 RDS 200 0 Maximum rooting depth allowed by the soil profile 1 1000 cm R
78. rainfall RAIN 0 1000 mm R Reference evapotranspiration E Tref 0 100 mm R Missing values in the input file should be indicated with 99 0 or lower The following rules apply to missing meteo data e missing values of rainfall are never allowed e if potential evapotranspiration must be calculated no missing values are allowed of the data RAD Imin Tmax HUM and WIND potential evapotranspiration will be calculated in case ETref values are not used specified in SWAP KEY section 3 or when ETref values are missing e no missing values for Tmin and Tmax are allowed if a crop is present or soil temperature must be simulated e no missing value for RAD is allowed in case the detailed crop model or the detailed grass model is active Violation of these rules cause program termination after first writing the date and the cause of the fatal error to the log file 4 4 Detailed rainfall stationR yyy Detailed rainfall data are necessary if runoff needs to be simulated accurately Each data record represents a reading from a raingauge which is empty at 00 00 hours and will be emptied again at the end of the day 24 00 hours This means that data entered should be cumulative over 24 hours Day month year hour and minute should be entered as integers Rain should be entered at least in tenth of a millimetre Note that in addition to the detailed rainfall also the daily rainfall amounts should be specified in file station yyy
79. report Van Dam et al 1997 the applied flow and transport concepts of SWAP and their background have been described This report describes the structure of the model and how the model can be used After the introduction chapter 2 starts with a brief summary of the system modelled by SWAP and the flow and transport processes considered Chapter 3 presents the model structure SWAP includes 7 sub models Meteo Crop detailed general detailed grass and simple Soil Irrigation and Timer One simulation may consist of 70 sequential or parallel sub runs SWAP calculates first the potential crop growth for the entire sub run period and next the actual crop growth in interaction with water flow solute transport and heat flow As the Soil sub model forms the heart of SWAP the order in which the boundary conditions and relevant processes are calculated in Soil is shown in detail The data flow to and from the sub models is discussed In order to adapt to a data base structure the input of different kind of data meteorology crop irrigation soil drainage surface water is divided over different input files In chapter 4 all the input files are described First an overview of required and optional input files is given including their general format rules Next the input files are discussed one by one while of each file an example is shown Chapter 5 explains the program execution and lists the output files that can be generated by the sub models Crop
80. reservoirs using the exponential rate coefficient defined here The effective lateral diffusion coefficient determines the rate of solute diffusion from the soil matrix to the bypassing water and has to be derived in the laboratory or from field measurements SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 157 Cracks are formed if the soil water content becomes smaller than a critical value The critical water content depends on the amount of clay and the clay mineralogy In case of moderately to heavy clay soils the critical water content is close to the saturated water content 4 11 10 Section 10 Vertical distribution of drainage flux solute transport with lateral drainage is to be simulated the drainage flux may be partitioned over the saturated layers If this option is not chosen SWAP assumes that the drainage flux leaves the model at the bottom compartment If only water flow is simulated or a relatively small section of a deep saturated profile is simulated this assumption is realistic However in case of solute transport and deep non uniform soils see also chapter in Van Dam et al 1997 the vertical distribution of drainage fluxes in the saturated zone 10 becomes important and should be taken into account this option is chosen anisotropy factors need to be defined for each soil layer The anisotropy factor is the ratio of the vertical over the horizontal saturated hydraulic conductivity The user s
81. the optional input file for the basic drainage routine DRB or the optional input file for the extended drainage routine DRE A A FF XE X F F x 4 the input file with the bottom boundary condition BBC 5 generic name of output files IRGFIL CALFIL DRFIL BBCFIL OUTFIL Hupsel Year80 Hupsel Hupsel Result End of table Section 5 Processes which should be considered SWDRA 1 Switch simulation of lateral drainage 0 No simulation of drainage 1 Simulation with basic drainage routine 2 Simulation with extended drainage routine SWSOLU 1 Switch simulation of solute transport 1 N 0 SWHEA 1 Switch simulation of heat transport Y 1 N 0 BG B X X KG KG KU KG KG KKK KKK KKK KK KKK KKK KKK
82. the availability of data Note that radiation and temperature data are necessary if the user specifies any of the options that use WOFOST Indicate the month and day of crop emergence this will be the day the model uses to start calculation of crop development stage and plant transpiration The emergence date should not be prior to an earlier crop s harvest date Indicate the harvest date which will also be the day yield will be calculated in the detailed crop model and transpiration calculation will be terminated The harvest date should not be later than a following crop s emergence date Indicate the day the scheduled irrigation should start In most cases this is the same as the date of crop emergence However a different date can be indicated according to the users preferences Filename Year80 cal Contents SWAP 2 0 Crop calendar
83. the crop part of living biomass dies due to senescence If simulation of crop growth is not needed the user might just prescribe leaf area index crop height rooting depth and root density distribution as a function of development stage SC DLO TECHNICAL DOCUMENT 53 DOC 11999 115 2 6 Soil heterogeneity Spatial variability of the soil hydraulic functions is described with the scaling concept of Miller and Miller 1956 The user may provide the reference curve and a number of scaling factors and SWAP will generate for each scaling factor the soil hydraulic functions and the corresponding water and solute balance and relative crop yield In cracked clay soils the shrinkage characteristic is used to determine crack volume area and depth Water and solutes collected in the cracks will infiltrate at the crack bottom into the soil matrix or flow rapidly to the surface water In the clay matrix the Richard equation is applied for water flow and the convection dispersion equation for solute transport Flow and transport in water repellent soil is based on the concept of a mobile and an immobile soil volume The actual mobile volume at a certain depth depends on the soil water pressure head In the mobile volume the Richards equation and the solute transport equation apply In the immobile volume the water flux is assumed to be zero Solutes diffuse between mobile and immobile volume 2 Irrigation and drainage Irrigation may be prescribed
84. tridiagonal matrix check hysteretic reversal and update scanning curve calculate water storage in soil profile and cracks surface water balance surface water balance PENMON PRHNODE QHTAB RACHAR RADATA RADIAT RADOUR RAINTR RAREAR RDBBC RDCRPD RDCRPS RDDRB RDDRE RDGRASS RDHEA RDKEY RDSLT RDSOL RDSWA REDUCEVA RFCHAR RFDOUR RFINTR RFREAR ROOTEX RSCHAR RSDATA RSDOUR RSINTR RSREAR SHIFTL SHIFTR SKPLBL SOIL SLTBAL SOILTMP SOLUTE STEPNR THENODE TIMER TOTASS TRIDAG UPDATE WATCON WBALLEV WLEVBAL 110 0 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 WLEVST surface water level from surface water storage WSTLEV surface water storage from surface water level ZEROCUMU reset cumulative water fluxes ZEROINTR reset intermediate water fluxes SC DLO TECHNICAL DOCUMENT 53 DOC 11999 1111 OC 11999 Annex 6 SWAP list with main variables first Angstrom coefficient fraction of surface area occupied by cracks threshold level high atmospheric demand cm threshold level low atmospheric demand cm array with adsorption flux crack matrix cm 6 array with alpha parameter in M VG functions cm array with alpha coefficient of weir discharge formula cm a altitude above mean sea level m instantaneous gross assimilation rate at light saturation kg ha h AFGEN table development stage gt max CO assimilation rate kg ha h maximum deviation from AQAVE cm
85. use the detailed crop model 4 8 1 Section 1 Crop factor or crop height Crop height or crop factor may used to determine the potential crop evapotranspiration If daily meteorological data are used as input paragraph 4 3 then both options are possible reference evapotranspiration is used as input then only crop factors can be used XX X KKK KKK KKK KKK KKK KKK KK KK KKK KKK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK KKK CK CK CK CK CK CK CK CK CK CK Filename WwheatD CRP Contents SWAP 2 0 Crop data of detailed crop model c Comment area SG c Winter wheat Tritium aestivum L KKK KKK KKK kkk KKK kk Section 1 Cro
86. 0 dis uge sJapuweJed 4 Program inputs 4 1 Introduction A summary of all input files the model can handle is given in table 1 Some files are required other files are optional The general input file named Swap key refers to the input files of the actual simulation Apart from the name of the file Swap key all file names can be freely chosen The file extensions are fixed however and indicated in bold in table 1 Other restrictions that apply to the file names are e The name of the meteo file with daily data consists of the name of the meteo station and an extension equal to last 3 digits of the year considered The optional file with detailed rainfall has an equal name with addition of an r before the extension see table 1 e A generic name is used for the input files swa soil profile description slt solute transport data and hea heat flow data In the example of table 1 the generic name is Hupsel Table 1 Summary of input file requirements Kind of data Description of file content kind of Filename Required Optional parameters General Simulation and I O options Swap key Meteo Daily data Hupsel yyy Detailed rainfall Hupselir yyy Irrigation Irrigation fixed Hupsel irg Irrigation calculated Irrig cap Crop Rotation Year80 cal Detailed non grass Maize crp Detailed grass Grass crp Simple crop model MaizeS crp Soil related Soil water Hupsel swa Soil hydraulic functions Sa
87. 0 0 End of table A X DCS2 1 Switch criterion Fixed Irrigation Depth 1 N 0 If DCS2 1 specify fixed irrigation depth 0 200 mm R as function of development stage 0 2 R maximum 7 records DVS FID 0 0 0 0 2 0 0 0 End of table X End of file KKK KK KKK KKK KK KKK KK KKK KKK KK RA File Irrig cap simulated irrigation sections 2 and 3 timing and depth of irrigation SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 133 4 7 Crop rotation cal Up to three crops can be simulated in each agricultural year using SWAP For each crop in a separate record crop type parameters emergence and harvest and irrigation scheduling should be specified Only one crop can grow in the field at one time so emergence and harvest dates should be sequentially and cannot overlap The file containing the crop parameters without the extension CRP needs to be indicated here The type of crop model should be indicated SWAP uses the crop model WOFOST 6 0 see Chapter 7 of Van Dam et al 1997 but the user can also choose to use a simple crop model which does not calculate crop development or can use WOFOST attuned to permanent grass During an agricultural year combinations of these three crop model types can be used The user s choice of detail in the crop model will depend on the user s interest in detailed output or
88. 0 0 0 00 0 30 04 1980 1 8 89 18 89 0 5 0 5 0 00 0 00 0 00 11 90 5 81 13 87 0 00 0 29 77 0 0 00 0 31 05 1980 152 19 82 19 81 0 5 O25 0 00 0 07 0 07 23 89 6 92 14 09 0 00 0 77 81 2 0 00 0 30 06 1980 182 26 44 25 63 0 5 0 5 0 0 3 70 3460 29 57 9 11 14 45 0 00 1 03 82 3 0 00 0 31 07 1980 213 41 01 8 0 5 0 5 0 00 11 07 8 51 8302632 7 21 233 0 00 0 73 78 5 0 00 31 07 1980 31 08 1980 244 45 65 4 0 5 0 5 000 20059 17 57 3 38 0 93 21 34 0 00 7 00 116 4 0 00 31 08 1980 30 09 1980 274 48 39 44 25 0 5 5 0 5 0 00 27 65 24 62 31 87 7 1 21 34 0 00 12 62 131 5 0 00 30 09 1980 31 10 1980 305 55 13 50 61 0 5 0 5 0 00 29 63 26 60 33 05 12 56 21 34 0 00 9 40 128 0 0 00 31 10 1980 30 11 1980 335 60 39 55 87 0 5 09 0 00 29 63 26 60 34 32 13 76 21 34 0 00 5 33 107 5 0 00 30 11 1980 31 12 1980 366 66 01 61 49 0 5 0 5 0 00 29 63 26 60 35 04 14 43 21739 0 00 0 44 78 8 0 00 31 12 1980 Output file Result sba DATE DAY SQTOP DECTOT ROTTOT SAMPRO SAMCRA SQBOT SQDRA SQRAP SAMAQ SQSUR SOLBAL dd mm yyyy nr mg cm2 mg cm2 mg cm2 mg cm2 mg cm2 mg cm2 mg cm2 mg cm2 mg cm2 mg cm2 mg cm2 lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt lt gt De lt gt lt gt gt 31 1 1980 31 0 5000E 03 0 0000E 00 0 0000E 00 0 5000E 03 0 0000E 00 0 0000E 00 0 7371E 06 0 0000E 00 0 0000E 00 0 0000E 00 0 3 29 2 1980 60 0 5000E 03 0 0000E 00 0 0000E 00 0 4996E 03 0 0000E 00 0 0000E 00 0 3522E 00 0 0000E 00 0 0000E 00 0 0000E 00 0 2 31 3 1980 91
89. 0 cal change the name of the crop data file CRPFIL to GrassS In the same file choose the simple crop type model Type 1 and set the SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 193 emergence date at 1 January and the end date at 31 December Verify the crop data in the file GrassS crp the leaf area index LAI 2 5 soil cover SC 1 0 crop height CH 15 cm and rooting depth RD 40 cm during the whole year 1980 You might check the pressure heads of the reduction function for root water extraction with Annex C Van Dam 1997 2 Goto Crop calendar Load file Year80 cal Change file with crop parameters to GrassS In this case we will also use the simple crop model Set the emergence date at 1 January and the harvest date at 31 December Goto Crop data simple model Load file grass crp Verify don t change the crop data the leaf area index LAI 2 5 soil cover SC 1 0 crop height CH 15 cm and rooting depth RD 40 cm during the whole year 1980 c Execute a simulation d Verify results Compare interception transpiration evaporation and drainage between the maize and grass cro p for the year 1980 Answer Fluxes Maize Grass Unit Interception 4 5 7 4 cm year Potential transpiration 29 6 54 9 cm year Actual transpiration 26 6 54 9 cm year Potential evaporation 35 0 0 0 cm year Actual evaporation 14 4 0 0 cm year Drainage 21 4 9 6 cm year Grass covers the soil the year round which cause compared to maize a large
90. 1997 The extinction coefficients and light use efficiency are needed to calculate a potential gross assimilation for the crop These determine how much radiation can be used for assimilation The assimilation rate is than reduced by either the phenological stage of the crop the average daytime temperature or a low minimum temperature at night when the assimilates are transformed The maximum CO2 assimilation rate AMAX is a function of the crop development stage The user can enter a specific relationship up to 15 data pairs to characterise this relationship The reduction factor TMPF based on average daily temperature accounts for sub optimum temperatures The input allows for a relationship defined by up to 15 data pairs The influence of a low minimum night temperature on the reduction factor of AMAX also can be defined by a relationship of up to 15 data pairs 36 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 8 6 Section 6 Conversion of assimilates into biomass The assimilates are transformed into structural biomass after subtraction of respiration for maintenance Depending on the product formed the efficiency of the conversion of primary photosynthates to structural plant material varies Efficiencies are crop specific and should be specified in this section 4 8 7 Section 7 Maintenance respiration An increase in temperature causes an increase in maintenance respiration Generally a 10 C temperature increase causes maintena
91. 1999 4 13 4 Section 4 Drainage and infiltration resistance A linear relationship between the average groundwater level and the drainage or infiltration flux is considered in this option Up to five different drainage levels can be specified For each level the user can specify whether drainage or infiltration or both are allowed Both the drainage and infiltration resistance needs to be specified by the user SWAP provides this option because is conceivable that the infiltration and drainage resistance differ because of differences in groundwater table local permeability or preferential flow to the drain The drain spacing does not need to be specified if the user has not chosen to distribute the drainage flux vertically file SWA section 10 Specify the level of the drainage medium bottom SWAP will determine the drainage base by taking the maximum of the drainage medium bottom and the surface water level If a channel is considered the water level in the channel as a function of time needs to be specified additionally RS CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK Filename Hupsel DRB Contents SWAP 2 0 Basic Lateral drainage AAA AAA kk kkk kk kk
92. 1E 198 T38 8 198 38 870 198 SO 826 198 SS 785 198 38 49 198 38 117 198 238 689 198 238 665 198 38 645 198 38 629 198 38 617 198 2349 608 198 230 604 NO X CO C OVO cC C 9 010 0 O C3 Q9 s CD CD CO 00 0 OQ C O OOO O OOOO Ss W 0 6 Cc 5 0 A COR 0 0 0 8 rn 6 60 r2 P2 OY tw WN C0 C0 C0 CO CO WwW OO ds Hs ds ds HA A WO Co N Co Y CO 1010 O O O CO O CCD OD OOO STO DO 00 000 000 EO OO CO CD CO CO CO 0 0 0 O O TO TOO OO OOOO VC 3 WU WUA 4s 01 01 0101001010101 1 NNN w mi wo OO T 0 OO QC GO O OO O dq CO CO CX CX CX CY C C9 CD C E E E E E E E E E E 0 9 OV OO O OO O OO O OO O QUO OO O OO 6 CX CY O OO O OVO O O O OO O O SPO QUO OO O O ONO OO O QO 0 10 00 O O O 8 e 8 o 8 e 8 0 o 8 0 o e 8 0 PT etn Y 100000 90 41 1000 O C0 O1 1 ON BABON 100 PO 00 010 WEA OO OO OOOO C OO CY O OO 0 00 6 O OO OO OCO O COLO OS O 6 O 2 90 00 00 0 Ov O O OQ OVO
93. 52 31 0 37 0 30 24 30 0 99 0 99 30 06 1980 182 61 0 73 4 18 143 81 0 97 0 97 31 07 1980 213 92 1 10 5 19 172 91 0 77 0 77 31 08 1980 244 123 1 46 5 74 179 95 0 85 0 85 30 09 1980 274 153 1 82 5 38 176 98 0 89 0 89 15 10 1980 289 168 2 00 5 20 175 100 0 90 0 90 with RELY relative crop yield 106 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Output file Result vap Wflux Sfl cm d mg cm2 1 338E 1 396E 107E 01 455E 105E 01 103E 01 563E 101E 01 609E S98 72 646E 2963E 673E 9382 68 728 LES 687E 833E 647E 701E 380E DOSE 164E 494E 58 72 417E 202E 341E 99g 2778 159E 221E 385E 173E 858E 134E 179E 981E 178E 772E 719E 657E 594E 532E 469E 406E 344E 281E 219E 156E 938E 313E ct 0 Oo x date depth water head solu E cm cm mg c 198 354 36 684 304E 198 2393 3 105 363E 198 2352 424E 198 352 37 948 485E 198 Soul 81307 54 62 198 350 38 780 603E 198 349 39 185 6555 198 39 580 699E 198 39 962 132E 198 40 328 753E 198 41 433 776E 198 42 513 541E 198 42 696 281E 198 41 962 119E 198 38 592 485E 01 198 34 353 175E 01 198 29 838 574E 198 337 z2542139 174E 198 So 20 322 495E 01 198 309 1 54 31 134E 01 198 S335 8 023 18
94. 9 Section 3 Meteorological data File name without extension of meteorological data 27 Latitude of meteo station 60 60 degrees R North METFIL Wageni LAT 920 SWETR 0 Switch use ETref values of meteo file Y 1 N 0 SWRAI 0 Switch use detailed rainfall data Y 1 N 0 1 ALT 10 0 Altitude of meteo station 400 3000 m R 1 1 RS CK CK CK CK Section 4 In and output files for the sub runs Specify for each simulation sub run max 70 the following 5 file names without extension absence of file as A8 1 the optional input file with fixed irrigation data IRG 2 the optional input file with the crop rotation scheme CAL 3
95. CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK KKK RS CK CK CK File grass crp detailed crop growth section 1 4 9 2 Section 2 Green surface area In the second assimilates limited growth stage the maximum increase in leaf area index is determined by the specific leaf area The specific leaf area of a grass crop can differ depending on the season SWAP allows for introduction of a curve describing the specific leaf area in up to 15 data points as a function of the daynumber To determine total assimilation it is necessary to know the green area of the stems since these can also absorb radiation 42 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Under optimal conditions constant 35 C leaves have a certain life soan Lower temperatures limit the life soan of the leaves Next to the optimal temperature of 35 C a lower threshold temperature which is crop specific should be entered 4 9 3 Section 3 Assimilation This section contains the parameters needed to calculate the assimilation rate from the solar radiation data Detailed information about the assimilation calculations can be found in Par 7 3 through 7 5 of Van Dam et al 1997 The extinction coefficients and light use efficiency are needed to calculate a potential gross assimilation rate for the crop The assimilation rate is than reduced by either the phenological stage of the crop the average daytime temperature or
96. Cumulative solute balance components sba Flux at soil surface Amount decomposed Amount taken up by plant roots Amount in soil profile Amount in cracks Flux at soil profile bottom Drainage flux Bypass flux from cracks Amount in defined saturated aquifer Flux from defined saturated aquifer Soil temperatures tep Soil temperature of nodes 1 6 11 etc Soil profiles vap Profiles of water content pressure head solute concentration temperature water flux and root water uptake Irrigation sc Calculated irrigation applications SC DLO TECHNICAL DOCUMENT 53 DOC 1 1998 1127 IC D 1999
97. E 139E 134E 128E 123E 118E 12E 1075 102E 875E 01 667E 01 516E 01 421E 01 354E 01 298E 01 256E 01 224E 01 1995 01 178E 01 1578 01 1418 01 132E 01 816E 01 974E 293 69 869 294 69 465 22 95 69 033 295 68 573 296 68 084 e297 67 567 298 67 022 298 9 9 65 849 300 65 273 304 63 248 310 59 438 cod 55 4 39 50 774 274 45 977 288 41 073 303 96 195 so T9 9 LUTO 334 26 203 348 21 222 366 Fl LO 2939 Sa OZ 238 6 239 8 0 23 38 26 224 IS 1 8 238 238 23 8 538 38 2538 238 366 0 366 zd 366 2s 366 7 366 4 366 m 366 0 366 Ts 366 7 366 7 366 366 366 366 A 366 Bs 366 ES Ta 366 42 366 47 366 EZ 366 A 366 IO 366 366 366 Ora 366 1 366 5 36 6 129 360 USD 366 145 3606 155 366 169 366 41 366 18D 366 T9 5 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 8 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 12 198 133E 154E 178E 205E 236E 270E 309E 436E 193E 136E 218E 325E 484E 115E 104E 145E LOSE 273E 291E 208E 108E 453E 01 152E 01 411E 943E 01 179E 01 251E 192E 000E 0002 0002 6 Oe CD C2 O CD CO CD
98. EGW from 200 to 180 cm File Hupsel swa section 4 variables NUMNOD and BOTCOM 2 change the number of compartments NUMNOD from 34 to 32 and the bottom compartment of the secondlayer BOTCOM 2 from 34 to 32 2 Two files need changes Goto Drainage basic and load file Hupsel drb Change the depth of the impermeable layer from 200 to 180 cm Goto Soil profile description and load file Hupsel swa At page 2 change the number of soil compartments to 32 Also change the compartment at the bottom of the second layer from 34 to 32 b Execute a simulation c Verify results Verify leaching of bromide for 1980 and 1981 files Result bal and Result2 bal How much bromide is leached to the drains on 31 December 1980 and 1981 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 199 Answer Depth impermeable layer m Year 2 00 1 80 Unit During 1980 39 5 46 3 mg cm During 1981 197 1 216 1 mg cm In the first year an increase of the impermeable layer with 0 20 m increases the bromide leaching from 39 5 to 46 3 mg cm 17 This may be important in case of pesticides In the second year the effect of the height of the impermeable layer is less 10 6 2 10 Preferential flow Field tracer studies may be affected by preferential flow due to water repellency or clay cracks In this exercise we will consider preferential flow due to water repellency in the top soil layer which may have a large impact on bromide leaching
99. EQ J K K KCTAB KDIF KDIR KF KFSAT KHBOT KHTOP KMEAN KMOBIL KSAT KSE99 KTABLE KVBOT KVTOP KYTAB L E LAI LAIEM LAITB LAT LAY number of the soil layer involved LAYER array describing in which soil layer a node is situated LCC length of the crop cycle d LDIS dispersion length cm LENGTH length of the table M METFIL name of the meteo station MOISRI moisture ratio at residual gt normal shrink MOISRD structural shrinkage MONTH month number N NIRD net irrigation flux cm d NMPER number of management periods NNCRACK node number for evaluating shrinkage characteristic NODE number of the current node NODGWL first unsaturated node counted from below NODHD array with compartment number related to HDEPTH NOFRNS number of runs NPHASE array with number of phases per management period NOH array with number of data pairs in QHTAB NRAI nett daily rainfall rate cm d NRLEVS number of drainage levels NRPRI number of drainage levels in primary system NRSEC number of drainage levels in secondary system NRSRF number of drainage levels NUMADJ counter for number of target level adjustments NUMBIT number of iterations NUMCOMP number of soil compartments NUMDRAIN number of drainage levels NUMLAY number of soil layers NUMNOD number of soil compartments O OSGWLM criterium for warning about groundwater
100. FGEN table with combinations of daynumber T and groundwater level cm H H array with pressure head at each node cm HAQUIF thickness aquifer for solute breakthrough cm HBWEIR array with height of weir crest cm HCRIT array with critical pressure head at HDEPTH cm HDEPTH array depth in soil profile for comparing with HCRIT cm neg HeaCap array with heat capacity of each compartment J cm K HeaCon array with thermal conductivity at each node J em K d HEAD pressure head at current node cm HGITAB AFGEN table with combinations of daynumber and pressure head of lowest compartment cm negative unsaturated HI array with initial pressure head of each node cm HLIMI start of root water extraction HLIM2L start of optimal extraction for all lower layers HLIM2U start of optimal extraction from upper soil layer HLIM3H end of optimal water uptake high atmospheric demand HLIM3L end of optimal water uptake low atmospheric demand HLIMA end of water uptake wilting point HMI H during previous timestep HOUR hour of the day solar time h HOHTAB array with hydraulic head above weir crest cm HSURF head top boundary condition cm HTABLE array with pressure head cm as a function of moist content HUM vapour pressure kPa HWLMAN pressure head used for target level cm I IDAY daynumber since January 1 IDSL switch for
101. I indicates if such a file will be used A file with detailed rainfall related to the meteo data file given above should have the name HupselR 998 4 2 4 Section 4 In and output files for the simulation runs A simulation run may comprise a period of 70 years Sequential run Alternatively up to 0 simulations for the same year or part of the year with changing input conditions for this year can be carried out parallel run A sequential run for more than one year or a parallel run for more than one case contains a number of sub runs Each sub run may have its own specific input data with respect to soil water boundary conditions and crop rotation scheme whereas each crop maximum 3 in the scheme is related to a specific model type detailed detailed grass only or simple cropping period and irrigation water application rules For each sub run the next filenames no extensions might be specified optional can be skipped SC DLO TECHNICAL DOCUMENT 53 DOC 11999 5 e IRGFIL optional input file with fixed irrigation data IRG Fixed irrigations are an alternative to calculated irrigations and can be applied both within and outside a cropping period e CALFIL optional input file with the crop rotation scheme CAL In case this file is not specified bare soil is assumed throughout the simulation period e DHFIL optional input file for the basic drainage routine DRB or the drainage routine extended to surface wate
102. IS 5 Dispersion length 0 100 cm R TSCE 0 Relative uptake of solutes by roots 0 10 R File hupsel sit solute data section 1 2 82 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Section 3 Adsorption SWSP 0 Switch consider solute adsorption 1 N 0 If SWSP 1 specify KF LO Freundlich coefficient 0 100 cm3 mg R FREXP 0 9 Freundlich exponent 0 10 R CREF 1 0 Reference solute concentration for adsorption 0 1000 mg cm3 R KEK KKK KKK KK KKK KKK KKK KK KKK AA KKK KKK KK KKK KKK KKK X
103. KK KK KKK KK KKK KK KK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KK KK KKK AAA AAA Section 10 Root density distribution and root growth List relative root density 0 1 R as function of rel rooting depth 0 1 R Rdepth Rdensity maximum 11 records RDCTB 0 00 1 00 1 00 0 00 End of table End of file RA File maizeS crp simple crop growth sections 7 0 52 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 11 Soil water and profile swa 4 11 1 Section 1 Ponding The maximum ponding layer thickness cm determines which water layer can be present on top of the soil surface before runoff starts 4 11 2 Section 2 Soil evaporation The conversion of potential soil evaporation from potential evaporation can be multiplied with a coefficient for soil evaporation This may be appropriate for instance if one applies the simple crop growht model
104. L3 20 Drain spacing 1 1000 m R ZBOTDR3 Level of drainage medium bottom 1000 0 cm R SWDTYP3 Type of drainage medium 1 Drain tube 2 Open channel case SWDTYP3 2 specify date day month and channel water level cm negative below field surface maximum 366 records mm LEVEL3 01 90 0 2 0 End of table SIE SIE a cde oe oe le ae k ok k File Hupsel drb example of a input file with data on basic drainage section 40 4c SC DLO TECHNICAL DOCUMENT 53 DOC A 1999 5 RS CK CK CK CK CK CK Section 4d Drainage to level 4 DRARES4 0 Drainage resistance 10 1E5 d R INFRESA 100 Infiltration resistance 90 1E5 d R SWALLO4 1 Switch for allowance drainage infiltration 1 Drainage and infiltration are both allowed 2 Drainage is not allowed 3 Infiltration is not allowed In case drainage fluxes should be distributed vertically in the saturated zone SWDIVD 1 in SWA specify the dista
105. N 0 End of file CK KKK KK KKK KKK KK KKK KK KKK KKK KKK KKK KK KKK KKK KKK KK RA File hupsel bbc bottom boundary conditions SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 177 4 16 Heat flow hea This file needs to be provided if the user has indicated simulation of heat transport in the SWAP KEY file section 5 Heat transport in SWAP can be simulated either analytically or numerically 4 16 1 Section 2 Analytical method The analytical method assumes soil thermal diffusivity and soil heat capacity to be constant In this case the heat flow equation can easily be solved assuming a sinusoidal variation of the temperature through the year The user should specify the mean amplitude and the daynumber with the maximum air temperature Additionally the user should specify the damping depth which is a function of the heat diffusivity See equation 4 8 in Par 4 2 of Van Dam et al 1997 No soil thermal properties need to be specified under this option 4 16 2 Section 3 Numerical method The initial soil temperatures should be entered SWAP uses the average daily temperature calculated form the meteo file station yyy as a top boundary condition and assumes a zero flux boundary at the bottom compartment In addition the soil thermal properties should be entered SWAP uses the fraction of clay sand and organic matter to calculate the soil ther
106. N table development stage gt specific leaf area ha kg array with slope of the pF FM relation slope of the pF FM relation specific pod area ha kg life span of leaves d under optimum temp amp light conditions cumulative solute amount through bottom soil profile mg cm cumulative solute amount profile lt drain ditch mg cm cumulative solute amount crack gt drain ditch mg cm cumulative solute amount saturated zone gt drain ditch mg cm cumulative solute amount through top soil profile mg cm specific stem area ha kg 9 character string to be left or right aligned array with surface water storage as a function of surface water level cm switch for output of formatted hydrological data switch for output of irrigation data array with switches for allowance drainage infiltration switch for output of soil profile data switch for output of soil temperature profiles switch for output of unformatted hydrological data active option for bottom boundary condition switch for simulation of drainage switch for output of drainage fluxes extended drainage option array with type of drainage media switch for use of ETref column in meteo files switch for hysteresis options switch for initial moisture condition options array with type of water management 1 fixed weir 2 automatic weir switch indicating if soil c
107. O CO CO WO CO CO CO CO CO CO CO CO y CO CO CO CO CO Y CO UY CO CO WWW CO CO INN INN Pe OVV NEN OY SY 0 OY 6 YN Y OO 00 0 62 rS P049 01 OO 0 11 00 00 OO H H SOOO C3 CX CX C CI CX C C CMN PO PO NNN PD O O WO hN O OWN SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 1107 IC D 1999 Annex B List of routines of Swap version 2 0 Purpose interpolate linearly in table check if line is blank or comment gross CO2 assimilation rate of the crop daylength astronomical and photoperiod calculate lower boundary conditions calculate basic lateral drainage calculate extended lateral drainage calculate top boundary conditions search for groundwater levels calculate crack shrinkage and swelling including fluxes WOFOST crop growth routine for SWAP simple crop growth routine for SWAP convert date into daynumber calculate soil thermal properties divide drainage flu
108. O O O O OS O Or 10 0 00 00 0 0 00 0000 N N CO O OOOO O OOOO O C 6 01 01 01 01 01 01 OF Ui Qa Or OT OT 0701 6 01 6 OT OT OT WWWWWW CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO C0 y WwW CO 0 1 0 0 CO O C9 Q9 CO 6 CO CO 0 0 0 0 0 00 QD C CO C23 C2 0 0 0 0 O C9 C9 CD CO CO CO CO CO CO CO CO CO CO Y CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO ln M A ME AAS EM LR A MM CC EC HR M TS ES OS SS SS n O O O O CO O OD COCO COCO COCO OOD 6 CO COO OOO OOO OOO OO OO 6 OO c a EA ke TE RR Ry OG RG RR ER ER RRO RG PR ES ERS ER RRS 662 66 602 6 c II FO OF OO 00 00 O O O DUO O N OC O C Co CX Cy O C5 C O Oo 0000000000 C OO O QD C5 C5 OO C2 CD C CO Ce 0 00 O QUO CO C C2 C C OOOO CY CX Cy C C O Nor 00050 10014 WN 31 07 1980 213 D 273 84 571 0 643E 00 18 2 0 429E 01 0 276E 01 31 07 1980 213 TIGO uc275 83 318 0 629E 00 1 0 438E 01 0 1 31 07 1980 213 2 5 0 276 82 068 0 666H 00 18 0 446E 01 0 1 31 07 1980 213 3 8 80 822 0 718E 00 18 0 453E 01 0 325E 0 31 07 1980 213 4 5 0 79 580 0 782E 00 0 0 459E 01 0 359E 0 31 07 1980 213 c0 Z8l 78 343 0 866E 00 18 0 0 465E 01 0 1 122E 141E 159E SLTSE SL98E 219E 241E 265E 289E 314E 382E 529E 01 699E 01 150E 145
109. OISRD 0 05 Structural shrinkage 0 1 cm3 cm3 R ZNCRACK 5 0 Depth at which crack area of soil surface is calculated 100 0 cm R GEOMF 3 0 Geometry factor 3 isotropic shrinkage 0 100 R DIAMPOL 40 0 Diameter soil matrix polygon 0 100 cm R RAPCOEF 0 Rate coef bypass flow from cracks to surface water 0 10000 d R DIFDES 0 2 Effective lateral solute diffusion coefficient 0 10000 d R Co if actual water becomes smaller than critical water content cracks are formed THETCR 0 35 0 40 Section 10 Vertical distribution drainage flux in saturated part soil column SWDIVD 1 Switch apply vertical distribution Y 1 N 0 Tf SWDIVD 1 specify anisotropy factor vertical horizontal saturated hydraulic conductivity for each soil layer max 5 0 1000 R COFANI Iso 1 0 TsO 1 0 15 20 ARA
110. SWAP will normalise the root density distribution Root growth is calculated rather straightforward The user needs to define the initial rooting depth the maximum daily increase and the maximum rooting depth The daily increase is equal to the maximum daily increase unless too few assimilates are available or the maximum rooting depth is reached 38 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Section 2 Crop development IDSL 0 Switch 0 Crop development before anthesis depends on temperature only 1 Crop development before anthesis depends on daylength only 2 Crop development before anthesis depends on both Tf IDSL 1 or 2 specify DLO Optimum daylength for crop development 0 24 h R DLC Minimum daylength 0 24 h R If IDSL 0 or 2 specify TSUMEA 1255 0 Temperature sum from emergence to anthesis 0 10000 C R TSUMAM 909 0 Temperature sum from anthesis to maturity 0 10000 C R List daily increase of temperature sum C R as function of av day temp
111. UTINC OUTSBA OUTSWB OUTTEP OUTVAP OUTWBA calculate potential evaporation and transpiration rates calculate pressure head from water content calculate discharge from water level with table read character array format free read array format free calculate fluxes of diffuse and PAR radiation read double precision array format free read integer array format free read real array format free read bottom boundary condition read crop data detailed model read crop data simple model read basic drainage read extended drainage and surface water read grass data detailed model read soil heat transport data read general input file SWAP read solute transport data read soil hydraulic functions read soil water and profile data calculate actual soil evaporation read fixed number character array read fixed number double precision array read fixed number integer array read fixed number real array calculate actual water extraction by roots read single character value read single data read single double precision value read singel integer value read single real value shift character string to the left shift character string to the right verify label and return position of general soil routine calculate of solute balance calculate of soil temperatures calculate solute concentrations find step number calculate water content from pressure head SWAP time keeper calculate daily total gross assimilation solve a
112. User s Guide of SWAP version 2 0 Simulation of water flow solute transport and plant growth in the Soil Water Atmosphere Plant environment J G Kroes J C van Dam J Huygen R W Vervoort Report 81 Dept Water Resources Wageningen Agricultural University Technical Document 53 DLO Winand Staring Centre Wageningen 1999 ABSTRACT Kroes J G J C van Dam Huygen and R W Vervoort 1999 User s Guide of SWAP version 2 0 Simulation of water flow solute transport and plant growth in the Soil Water Atmosphere Plant environment Wageningen Agricultural University Report 81 DLO Winand Staring Centre Technical Document 53 128 pp 6 fig 3 tab 20 ref This manual describes how the numerical model SWAP version 2 0 can be used to simulate vertical transport of weater solutes and heat in variably saturated cultivated soils A brief theoretical description is followed by a technical description of model structure and general data flow An extensive explanation is given of program inputs and outputs based on ASCII text files The manual ends with examples using important features of the model Keywords agrohydrology drainage evapotranspiration irrigation salinization simulation model SWAP soil water soil heat soil heterogeneity surface water management ISSN 0927 4499 1999 DLO Winand Staring Centre for Integrated Land Soil and Water Research SC DLO P O Box 125 NL 6700 AC Wageningen The Netherlands
113. X one file covers the total simulation period SWAFO 0 Switch output file with formatted hydrological data Y 1 N 0 AFONAM Result File name without AFO extension A8 SWAUN 0 Switch output file with unformatted hydrological data Y 1 N 0 AUNNAM Result File name without AUN extension A8 SWATE 0 Switch output file with soil temperature profiles Y 1 N 0 ATENAM Result File name without ATE extension A8 SWAIR 0 Switch output file with irrigation data Y 1 N 0 AIRNAM Result File name without AIR extension A8 End of file File swap key with general information section 3 4 5 6 and 7 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 7 4 3 Daily meteo data station yyy SWAP uses daily evapotranspiration data Also the rainfall data should be specified for each day but in addition the actual rainfall intensities may be specified in the file stationnr yyy The ranges units and datatype of the meteo data are Daily global Radiation RAD Minimum temperature Tmin 50 35 C R Maximum temperature Tmax 30 60 6 R Average vapour pressure HUM 0 10 kPa R Average windspeed WIND 0 50 m sec R Total
114. a node cm em array with initial moist content of each compartment cm cm array with nodal residual water content cm em array with nodal saturated water content cm cm critical theta for depth of cracks array with pointer to highest theta values in HTABLE array with volumetric water content in immobile soil parts cm cm array with pointer to lowest theta values in HTABLE array with nodal moisture content at previous time step cm cm stop criterium iteration procedure array with saturated volumetric water content of each layer cm cm array with thickness of the compartments cm time at start of sine temperature wave day mean annual temperature at soil surface C AFGEN table low minimum temperature C gt reduction factor of AMAX AFGEN table average temperature C gt reduction factor of AMAX solute root uptake factor temperature sum from anthesis to maturity C temperature sum from emergence to anthesis C array with critical unsaturated volume cm water storage in the soil profile cm initial total volume of water in the soil profile cm VOLACT during previous time step cm volume of water in the saturated soil profile cm total air volume in soil profile cm moisture content at current node array with wet perimeter of the drains cm array with bottom width of channel cm windspeed a
115. al in many automated systems The user should specify the depth of the sensor Each of the options gives the opportunity to define the timing criteria as function of crop development stages giving the possibility of dynamic irrigation scheduling It is conceivable that a crop can be allowed different levels of water and or salinity stress depending on its development stage SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 131 4 6 3 Section 3 Irrigation depth criteria The back to field capacity option is useful in the case of sprinkler or micro irrigation SWAP calculates the amount of irrigation water needed to bring the pressure heads in the root zone until h 100 cm An over positive or under negative irrigation amount 0 100 mm R can be specified depending on the development stage of the crop This can be useful if salts need to be leached or regular rainfall is expected The fixed depth irrigation 0 200 mm R is generally used when gravity irrigation systems are simulated which generally allow little variation in application depth Again it is possible to specify the irrigation amount depending on the crop development stage X X KKK KK KKK KKK KKK KKK KKK KKK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK CK CK CK CK CK CK Filename IRRIG CAP Contents SWAP 2 0 Irrigation scheduling criter
116. alculate ESO from ETO ETR or ESO If SWCFBS 1 then specify 0225 else a dummy value may entered for CFBS CFBS 1 0 Coefficient for soil evaporation 0 5 1 5 R SWREDU 1 Switch method for reduction of soil evaporation reduction to maximum Darcy flux reduction to maximum Darcy flux and to maximum Black 1969 reduction to maximum Darcy flux and to maximum Bo Str 1986 N 6 COFRED 0 35 Soil evaporation coefficient of Black 0 1 cm d1 2 R or Boesten Stroosnijder 0 1 cm1 2 R RSIGNI 0 5 Minimum rainfall to reset models Black and Bo Str 0 1 cm d R DA E RS Section 3 Time discretization of Richards equation d R d R DTMIN 1 0E 5 Minimum timestep 1 E 8 0 DTMAX Maximum timestep 0 01 SWNUMS Type of implicit scheme 5 1 Richards equation is solved twice per time step 2 Richards equation is solved until convergence use in general THETOL 0 001 Maximum dif water content between iterations 1 E 5 0 01 cm3 cm3
117. allel run 0 array with hydraulic conductivity at each node lower boundary cm d AFGEN table development stage gt crop factor al extinction coefficient for diffuse light extinction coefficient direct light Freundlich adsorption coefficient cm mg linear adsorption coefficient aquifer cm mg horizontal hydraulic conductivity bottom layer cm d horizontal hydraulic conductivity top layer cm d array with arithmetic mean hydraulic conductivity between a node and the one above cm d exchange rate between mobile immobile parts d array with saturated hydraulic conductivity of each layer cm d array with hydraulic conductivity at relative saturation of 0 99 cm 4 a function of moisture content array with hydraulic conductivity cm d as vertical hydraulic conductivity bottom layer cm d d vertical hydraulic conductivity top layer cm table development stage gt yield response factor array with spacing between channels drains cm leaf area index ha ha leaf area index at emergence ha ha AFGEN table development stage gt leaf area index ha ha SC DLO TECHNICAL DOCUMENT 53 DOC 11999 1117 geographical latitude degrees ILTAB IMPEND IMPER INDEX INFRES INPOLA INPOLB INQ INQDRA INQROT INTWL IPEVA IPOS IPREC IPTRA IQBOT IQCRACK IQDRA IQDRAR IQROT IRUNNR IRUNO ISCLAY IS
118. and drainage for the simulation that uses the leaf area index reference and the simulation that uses the soil cover to divide the potential evapotranspiration 94 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Answer Fluxes LAI SC Unit Potential transpiration 29 6 35 5 cm year Actual transpiration 26 6 33 0 cm year Potential evaporation 35 0 29 6 cm year Actual evaporation 14 4 11 4 cm year Drainage 21 4 18 1 cm year The simulated water balance for both cases is clearly different A proper division of potential evapotranspiration in potential transpiration and potential evaporation is needed to achieve an accurate water balance 6 2 5 Soil texture During this exercise you will investigate the effect of changes in soil texture Initialise with reference situation described in par 6 1 execute INITIAL BAT a b Change input 1 Two changes are needed Change in the soil water file Hupsel swa section 5 the names of hydraulic function files to Clayt clay top soil and Clays clay sub soil Change in the input file Hupsel drb section 3 variable KHTOP the saturated conductivity for a calculation of the drainage flux from 25 to 2 5 cm d 2 Two changes are needed Qoto Soil Profile description Load file Hupsel swa At page 2 change the names of the files with the soil hydraulic functions The first layer should be Clayt clay top soil and the second layer Clays clay sub soil
119. at fixed times or scheduled according to a number of criteria The scheduling option allows the evaluation of alternative application strategies The timing criteria include allowable daily stress allowable depletion of readily available water in the root zone allowable depletion of totally available water in the root zone and critical pressure head or water content at a certain depth Field drainage can be calculated with a linear flux groundwater level relationship with a tabular flux groundwater relationship or with drainage equations of Hooghoudt and Ernst The use of drainage equations allows the design or evaluation of drainage systems 2 8 Surface water system At sub regional level the interaction between soil water balance crop growth and surface water management can be simulated The surface water system can be partitioned in up to five channel orders each defined by its bed level bed width side slope and spacing In each channel except from the primary channel the surface water has the same level which is either input or calculated from the sub region water balance The water level of the primary channel is input Drainage to each channel order is calculated with the corresponding drainage resistances Also infiltration from the channels using the corresponding infiltration resistances is calculated when the surface water level is higher than the groundwater level In case of surface water level as output for each water managemen
120. ater content This shows the importance of correct initial moisture conditions for water balance analysis Several years without rainfall 6 2 2 2 We will see what happens if the period without precipitation continues for a second year a Change input 1 Inthe file swap key changes must be made in 2 sections Section 2 Time variables The simulation period must be changed Extend the simulation period until 31 December 2001 and set output dates at the end of each month in each year Section 4 Input and output files Specify the input files for the second year for fixed irrigation crop rotation Year80 drainage Hupsel and bottom boundary condition Hupsel In this way the boundary conditions are the same as the first year except that the bromide tracer is only applied the first year Specify the generic name for the output files for year 2001 as Result2 2 Goto Key Load SwapGui key on directory c swap examples exercise Change the following Atsection Timing Extend the simulation period to 1 January 2000 31 December 2001 and set output dates at the end of each month in each year Atsection Sub runs Specify the input files for the second year for fixed irrigation crop rotation Year80 drainage Hupsel and bottom boundary condition Hupsel In this way the boundary conditions are the same as the first year except that the bromide tracer is only applied the first year Specify th
121. ater level The maximum of the surface water level and the channel bed level will be used to calculate the drainage base 4 13 2 Section 2 Table of drainage flux groundwater relation This option should be used if the relationship between Qgrain and the groundwater level is non linear SWAP will linearly interpolate between the specified values The drain spacing should be entered in m The drain spacing does not need to be specified if the user did not partition the drainage flux vertically file SWA section 10 4 13 3 Section 3 Drainage formula of Hooghoudt or Ernst Another option to calculate drainage is to use the formulas of Hooghouat 1940 and Ernst 1956 which calculate stationary groundwater flow from to surface water Five typical drainage situation can be chosen figure 5 On top of an impervious layer in a homogeneous profile Above an impervious layer in a homogeneous profile At the interface of a fine upper and a coarse lower soil layer In the lower more coarse soil layer In the upper more fine soil layer SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 161 A more complex drainage situation will demand an increasing number of input parameters Most of these parameters are self explanatory The geometry factor of Ernst Gar 0 100 R can be determined from van Dam et al 1997 table 8 1 and is listed below The geometry factor depends on the ratio of the hydraulic conductivity of the bottom Knot and t
122. ather data belong to the year 1980 which is more or less an average meteorological year for the considered region Daily rainfall data are used as surface runoff is not expected The climatic conditions are such that no irrigation is needed The field is cultivated with maize which emerges 1 May and is harvested 15 October Maize growth is not simulated but instead the simple crop routine is selected to prescribe SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 187 leaf area index soil cover crop height and rooting depth as function of development stage see Table 3 A triangular root density distribution is assumed The soil profile contains loamy sand both in the top and in the subsoil The soil hydraulic data of the two soil layers are derived from Wosten et al 1994 Van Dam et al 1997 Annex A In the reference case no hysteresis or scaling of the soil hydraulic functions is considered Also preferential flow due to immobile soil volumes or shrinkage cracks is not taken into account Drains are located at 0 80 m depth and are spaced 11 m apart An impermeable boulder clay layer occurs at 2 0 m depth For calculation of solute breakthrough curve to the surface water the mean thickness of the phreatic aquifer is estimated at 1 10 m Figure 7 gives an overview of the considered case Weather data 1980 Maize crop May 1 October 15 Application tracer bromide January 5 0 30 5 Top soil sand I 0 80 Sub soil sand Do Subsurface drains
123. caling 1 N 0 If SWSCAL 1 specify NSCALE 3 Number of runs 1 30 I ISCLAY 2 Number of soil layer to which scaling is applied 1 5 I List scaling factor of each run max 30 0 100 R FSCALE 0 45 1 00 2 50 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 0 00 End of table File hupsel swa example of a file with soil water and profile data section 4 7 56 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 11 8 Section 8 Preferential flow due to immobile water SWAP allows for simulation of preferential flow due to unstable wetting fronts e g in case of water repellent soils The soil is divided in a mobile or transport domain and an immobile or resident domain Exchange of solutes between the two domains is governed by the exchange of water and diffusion of solutes The solute exchange coefficien
124. centration in soil water mg cm array with solute concentration in mobile soil water mg cm array with initial solute concentration per compartment mg cm array with total concentration solved absorbed in mobile volume mg cm cumulative net irrigation depth cm cumulative net rainfall cm SC DLO TECHNICAL DOCUMENT 53 DOC 11999 3 A A ACRACK ADCRH ADCRL ADSFLU ALFAMG ALPHAW ALT AMAX AMAXTB AQAMP AQAVE AQOMEG AQTAMX ARFLUX ATMDEM AVRAD B B BASEGW BAYRD BAYRY BDENS BETAW BEXP BOTCOM BRUND BRUNY C CDRAIN CEVAP CGIRD CGRAI CH CHTAB CIL CIRR CISY CKWMI CL CML CMLI CMSY CNIRD CNRAI precipitation interception coefficient array with anisotropy factor of each layer array with Van Genuchten parameters coefficient A in flux groundwater level relationship cm d coefficient B in flux groundwater level relationship cm d soil evaporation coefficient cm d or cm amplitude of sine of solar height cumulative potential soil evaporation cm solute concentration in ponding water mg cm solute concentration in rain water mg cm cumulative potential transpiration cm cumulative flow depth through bottom of profile cm cumulative flow from cracks into matrix cm cumulative total drainage flow depth cm array with cumulative drainage flow depth per drainage level cm cumulative rapid drainage flow d
125. cify maximum amount of water depleted below field cap 0 500 mm R as function of development stage 0 2 R maximum 7 records DVS DWA 0 0 40 0 2 0 40 0 F X End of table TCS5 0 Switch criterion pressure head or moisture content 1 N 0 If 7055 1 specify PHORMC 0 Switch use pressure head PHORMC 0 or water content PHORMC 1 DCRIT 30 0 Depth of the sensor 100 0 cm R Also specify critical pressure head 1 0E6 100 0 cm R or moisture content 0 0 1 0 cm3 cm3 R as function of development stage DVS 0 0 2 0 RJ DVS VALUE 0 0 1000 0 2 0 1000 0 End of table KK KKK KK KKK KKK KK KKK KKK KKK KKK KKK KKK KKK KKK KK KKK KKK KKK KK KKK KKK CK Section 3 Irrigation depth criteria Choose one of the 2 options DCS1 1 Switch criterion Back to Field Capacity 1 N 0 If DCS1 1 specify amount of under or over irrigation 0 100 mm RJ as function of development stage 0 2 R maximum 7 records DVS dI 0 0 0 0 2 0
126. course the user may choose to define the soil as surface reference level by specifying zero for the altitude 4 14 2 Section 1 drainage characteristics Section 1 starts with the specification of the drainage resistance for surface runoff Ysin A value of 0 1 d will be appropriate in most cases The maximum ponding depth ziii is defined in the input file with soil water and profile data file extension SWA The process of surface runoff is complicated and the user should be aware of the simplifications of reality applied to simulate surface runoff Van Dam et al 1997 chapter 9 Next follows the specification of the number of drainage levels n This excludes the surface runoff Section 1 continues with the specification of the orders of drainage channels in the input denoted as levels at maximum 5 levels can be handled In the module for extended drainage level 1 involves the deepest channels in the considered subregion This does not have to be the primary system it can also be the secondary system in that case the primary system is absent Per level the user can specify whether it concerns channels or drains So the user may specify that all of the levels are pipe drains Apart from specifying its type per drainage level the user must specify the following parameters representative spacing between channels Lgrain m bottom width of channel bed only for channels Warain cm groundwater level for
127. d the input data for a fixed irrigation schedule These input must be specified in a file with extension IRG and must be given for each year with fixed Irrigations as indicated in SWAP KEY section 4 The type of irrigation can be specified as being a sprinkling 0 or a surface 1 irrigation In case of sprinkling irrigation interception will be calculated X BG XB AAA KK KKK KKK KKK CK KKK KK KKK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK CK CK CK CK CK CK Filename Hupsel IRG Contents SWAP 2 0 Fixed Irrigations Comment area Case Water and solute transport in the Hupsel area a catchment in the eastern part of the Netherlands Example of the User s Guide reference situation A set of input data to explore SWAP
128. de leaching in the second experimental year Also we will analyse the influence of the depth of the impervious layer 6 2 9 1 Breakthrough during a 2 year period During this first part of the exercise you will calculate the breakthrough of the bromide during a two year period a Initialise with reference situation described in par 6 1 execute INITIAL BAT b Change input 1 Inthe file Swap key changes must be made in 2 sections Section 2 Time variables extend the simulation period to 31 December 1981 and specify monthly output dates for the years 1980 and 1981 1981 is no leap year Section 4 Input and output files Specify the input files for the second year for fixed irrigation crop rotation Year80 drainage Hupsel and bottom boundary condition Hupsel In this way the boundary conditions are the same as the first year except that the bromide tracer is only applied the first year Specify the generic name for the output files for the year 1981 as Result2 2 Goto Key and load file SwapGui key Changes must be made in 2 sections n section Timing set the end of the simulation period to 31 December 1981 and specify output dates at the end of each month for 1981 no leap year 98 A SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 In section Subruns specify the input files for the second year for fixed irrigation crop rotation Year80 drainage Hupsel and bottom boundary condition
129. density distribution bromide breakthrough to surface water drainage design After carrying out the exercises the reader should be able to use SWAP for his her own agrohydrologic research In paragraph 6 1 the reference situation is described and in paragraph 6 2 exercises are discussed Additional input files are supplied in the directory DATA e Daily weather data of Wageningen meteo station for a period of 40 years 1954 1993 e Data files for detailed crop growth at West European conditions of winter wheat grain maize spring barley rice sugar beet potato field bean soy bean winter oil seed rape and sunflower as adapted from Prins et al 1993 e Soil hydraulic functions of the Staring Series Wosten et al 1994 6 1 The reference situation The input files that are required to carry out the exercises are supplied with the program The input data files for the reference situation are located in the directory REFERENC These data should not be changed and serve as initial condition for the exercises discussed in par 6 2 6 1 1 Introduction In the reference run a simulation is carried out for water and solute transport in the variably saturated zone at an experimental field in the Hupsel catchment in the East of the Netherlands Measured meteorological data of the Wageningen weather station are used to calculate evapotranspiration according to the Penman Monteith equation Van Dam et al 1997 par 6 2 The we
130. distribution is defined Execute a simulation d Verity results Analyse transpiration evaporation drainage and groundwater levels for the triangular and uniform root density distribution SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 197 Answer Fluxes Triangular Uniform Unit Potential transpiration 29 6 29 6 cm year Actual transpiration 26 6 21 6 cm year Potential evaporation 35 0 35 0 cm year Actual evaporation 14 4 14 4 cm year Drainage 21 4 25 1 cm year Groundwaterlevels Triangular Uniform Unit 31 March 70 0 70 0 cm 30 November 107 5 87 5 cm In case of the uniform root distribution the actual transpiration sharply reduces to 21 6 cm A large reduction occurs in the lower wet part of the root zone In the current model concept water stress at a certain soil depth is not compensated for by higher root water uptake at another soil depth Therefore in case of shallow groundwater levels be sure that the appropriate rooting depth and distribution are used 6 2 9 Bromide breakthrough to surface water Tracer studies in the field that include both the unsaturated and saturated zone may require a duration of several years In the reference situation par 6 1 after one year only 39 5 mg cm out of 500 mg cm is leached to the drains After one year only a small amount of bromide has reached the groundwater level which you may verify from the solute profiles in output file Result vap In this exercise we will simulate bromi
131. drainage flux into surface reservoir cm d array with drainage flux gt gt groundwater level relationship total drainage flux cm d array with flow depth per node to from immobile phase cm array with related see HOHTAB discharge cm d total rootwater extraction flux cm d array with root extraction flux per node cm d top boundary flux cm 0 incoming short wave radiation J m d POND PONDMI PONDMX POROS PTRA Q Q Q10 QBOT QBOTAB QCRACK QDRA QDRAIN QDRD QDRTAB QDRTOT QIMMOB QQHTAB QROSUM QROT QTOP R RAD RAPCOEFF rate coefficient bypass flow from cracks to drains d bypass flow rate to drains ditches cm d reflection coefficient crop reflection coefficient soil maximum rooting depth crop cm table datapairs of root distribution coefficient as a function of fraction of maximum rooting depth initial rooting depth cm maximum rooting depth cm array with drainage resistance d AFGEN table development stage gt rel death rates of roots kg d maximum rooting depth allowed by the soil cm AFGEN table development stage gt rooting depth cm array with entry resistance d relative error in stop criterium for calculation of non linear ads actual soil evaporation rate cm d array with exit resistance d AFGEN table development stage gt reductio
132. e generic name for the output files for year 2001 as Result2 b Execute a simulation c Verify results Compare transpiration and evaporation for 2000 and 2001 files Result wba and Result2 wba Also compare relative crop yield for both years files Result cr1 and Result2 cr1 Answer Fluxes 2000 2001 Unit Potential transpiration 30 7 30 8 cm year Actual transpiration 27 1 12 2 cm year Potential evaporation 35 0 34 9 cm year Actual evaporation 4 4 1 7 cm year Crop growth 2000 2001 Unit Relative yield 0 88 0 40 92 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 The crop in the second year can only transpire 40 of the potential transpiration which will severely hamper crop development 6 2 2 3 Surface irrigation This exercise shows what will happen if the previous simulation is continued automatic irrigation scheduling for both years a Change input 1 Specify in the crop calendar file Year80 cal variabel CAPFIL the input file for irrigation scheduling Irrig cap and set emergence data at 1st of May Verify no changes required in the input file Irrig cap Section 2 the Ratio for allowable Daily Stress Ta Tp which should be equal to 0 95 during the entire growing period Also verify in the same file Irrig cap Section 3 the irrigation depth criterium which should be Back to Field Capacity without under or over irrigation 2 Goto Crop calendar Load file Year80 cal Specify the input file for
133. e modelled the following parameters should be specified e thickness of the aquifer for solute breakthrough cm e porosity of the aquifer e linear adsorption coefficient for the aquifer em mg specify O if no adsorption takes place e decomposition rate in the aquifer d e initial solute concentration in the aquifer mg cm SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 181 Filename Hupsel SLT x Contents SWAP 2 0 Solute data RS CK CK CK CK CK CK KKK KKK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK Comment area Case Water and solute transport in the Hupsel area a catchment in the eastern part of the Netherlands Example of the User s Guide reference situation A set of input data to explore SWAP
134. e with data for time increments Result bal Water balance with data cumulative over time and vertical space Result sba Solute balance Result tep Soil temperature Result vap Soil moisture solute and temperature profiles Result cr1 crop growth status Furthermore 3 additional files are generated Swap207 log a file with error messages Hfinal dat a file with final pressure heads of all compartments Suc cex an empty file which is only used by the Graphical User Interface The SWAP output annex A file Result wba shows that the maize potential transpiration during 1980 equals 29 63 cm while the maize actual transpiration of this year equals 26 60 cm The drainage in 1980 amounts 21 39 cm The groundwater level reaches its maximum at 31 March 70 0 cm and its minimum at 30 September 131 5 cm The water balance increments output file Result inc show a small amount of irrigation water which is caused by the application of bromide Of the 500 mg cm bromide applied 39 5 mg cm has reached the surface water at 31 December The main amount of bromide is still in the soil profile The maize relative yield annex A file Result cr1 amounts 0 90 which is equal to the ratio of actual transpiration and potential transpiration 26 60 29 63 6 2 Exercises The exercises are carried out on directory EXAMPLES EXERCISE Each exercise uses the reference situation of the previous paragraph as starting point
135. ecify mobile fraction as function of log h for each soil layer 1 first datapoint log h cm 0 5 R FM1 first datapoint mobile fraction 1 0 totally mobile 0 1 R PF2 second datapoint log h cm 0 5 R FM2 second datapoint mobile fraction 1 0 totally mobile 0 1 R Also specify volumetric water content in immobile soil volume THETIM 0 0 3 R PF1 FM1 PF2 FM2 THETIM 0 0 0 4 3 0 0 4 0 02 0 0 T0 3 0 1 0 0 02 End of table ox 06 A Xo Xo X Section 9 Preferential flow due to soil cracks SWCRACK 0 Switch soil cracks Y 1 N 0 Tf SWCRACK 1 specify SHRINA 0 53 Void ratio at zero water content 0 2 cm3 cm3 R MOISR1 1 0 Moisture ratio at trans residual gt normal shrinkage 0 5 cm3 cm3 R M
136. epth cm cumulative total drainage flow into surface water reservoir cm cumulative root water uptake cm cumulative flow depth through top of profile cm solute concentration in cracks mg em water storage 1n cracks cm level of the crack bottom cm reference solute concentration for adsorption mg cm reference solute concentration for adsorption mg cm cumulative surface runoff cm efficiency of conversion into leaves kg kg efficiency of conversion into storage organs kg kg efficiency of conversion into roots kg kg efficiency of conversion into stems kg kg cumulative surface water discharge cm cumulative surface water supply cm day number since beginning of the month daynumber since start of calendar year of first date daynumber since start of calendar year of second date astronomical daylength h photoperiodic daylength h day number since beginning of the calendar year daynumber calendar year at start of simulation run damping depth cm molecular diffusion coefficient cm day potential transformation rate d transformation rate in aquifer d cumulative solute amount transformed mg cm diameter soil matrix polygon cm effective lateral diffusion coefficient d array with differential moisture capacity at each node cm array with distance between a node and the one above cm
137. erature This implies that the user has to specify the weir characteristics that define a relationship of the following form Q Q input HP 6 where Q is the discharge m s H is the head above the crest m and aj is a weir coefficient m P s B is a weir exponent The only preparatory work that the user has to do is to compute the value of Olinput from the various coefficients preceding the upstream head above the crest For instance for a broad crested rectangular weir Ginput is approximately given by OQ input 7b 7 where 1 7 is the discharge coefficient of the weir based on Sl units bis the width of the weir m 70 0 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 To correct for units the model carries out the following conversion 8 64 100 P Wale m Olinpur 8 Acu where Aj is the size of the control unit ha The model requires input of the size of the control unit Ac which in simple cases will be identical to the size of the simulation unit Section 4d For each water management period with a fixed weir crest using weir data the user should specify a table Section 4e For each water management period with an automatic weir the user should specify e index of the management period e the maximum allowed drop rate of the water level setting e the depth HDEPTH in the soil profile for the pressure head criterium HCRIT Within each management period the water level of a secondary watercou
138. f Mualem Van Genuchten 1980 ko ko ko ko ko ko ko ko ck ko ko ko ko ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck Ck Ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck CA Section 2 Table Specify pressure head cm negative and hydraulic conductivity cm d as function of water content cm3 cm3 start with the lowest water content corresponding pressure head should be smaller than x 1 0E6 and use increments of 0 01 until the saturated water content theta H theta K theta 5 658312E 06 5 678438E 10 0 020 3 863693E 04 3 599819E 08 0 030 0 000000F 00 9 650000E 00 0 430 End of table ko ko ko ko ko ko ko ko ko ko KKK ck ck ck ck Ck ck ck ck ck ck
139. f development stage 0 2 R oi DVS FR maximum 15 records FRTB 0 00 0 50 0 10 0 50 0 20 0 40 0 35 0 22 0 40 0 17 0 50 0 13 0 70 0 07 0 90 0 03 O 0 00 2 00 0 00 tabl List fraction of total above ground dry matter incr part to the leaves kg kg R as function of development stage 0 2 R DVS FL maximum 15 records FLTB 0 0 65 0 10 0 65 0 25 0 70 0 50 0 50 0 70 D 515 0 95 0 00 2 00 0 00 End of table List fraction of total above ground dry matter incr part to the stems kg kg R as function of development stage 0 2 R DVS FS maximum 15 records FSTB 0 D 35 0 10 0 35 0 25 0 30 0 50 0 50 0 70 0 85 0 95 1 00 1 05 0 00 2 00 0 00 End of table List fraction of total above ground dry matter incr part to the st organs kg kg R as function of development stage 0 2 R End of e DVS FO maximum 15 records FOTB 0 00 0 00 0 95 0 00 1 05 1 00 2 00 1 00 End of table Ck CA CK Ck CK C CK CK CK CC KKK KK KKK KKK KK KKK KK KKK KKK KK KKK KK KKK KKK KKK KKK KKK KK KKK KK KKK KKK KK KKK KKK RA File wheatd crop detailed crop growth section 7 and 8 40 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 RA
140. ficiency of single leaf 0 10 kg ha hr Jm2s R List max CO2 assimilation rate kg ha hr R as function of time 0 366 d R Ei TIME AMAX maximum 15 records AMAXTB 0 40 0 95 20 40 0 200 0 35 0 275 0 25 0 366 0 25 0 End of table List reduction factor of AMAX R as function of average day temp 10 50 C R i ADT TMPF maximum 15 records TMPFTB 0 0 0 5 00 0 70 15 00 1 00 25 00 1 00 40 00 0 00 End of table List reduction factor of AMAX R as function of minimum day temp 10 50 C R TMNF maximum 15 records TMNFTB 0 00 0 00 4 00 1 00 End of table ck ck ck ck Ck ck ck ko ko ko ko ko ko ko ko ko kk Section 4 Conversion of assimilates into biomass CVL 0 685 Efficiency of conversion into leaves 0 1 kg kg R CVR 0 694 Efficiency of conversion into roots 0 1 kg kg R CVS 0 662 Efficiency of conversio
141. ge 21 4 22 7 cm year Groundwaterlevels No Hyst With Hyst Unit 31 March 70 0 0 5 cm 30 September 131 5 129 7 cm At the present hydrological conditions hysteresis hardly affects the water balance and groundwater levels 6 2 7 Scaling of soil hydraulic functions Horizontal variability of the soil hydraulic functions can be taken into account by scaling according to Miller and Miller see Par 5 1 2 Van Dam 1997 In SWAP you may supply up to 30 scaling factors The program will generate the actual soil hydraulic functions out of the reference soil hydraulic functions and perform a simulation for each plot Just to 96 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 practise how this works we will use three scaling factors 0 45 1 00 and 2 50 The second simulation with scaling factor 1 00 corresponds to the reference simulation a Initialise with reference situation described in par 6 1 execute INITIAL BAT b Change input 1 In file Hupsel swa section 7 choose the option scaling for 3 repetitions and apply the scaling to the top layer Supply the three scaling factors 0 45 1 00 and 2 50 2 Goto Soil Profile description Load file Hupsel swa At page 3 select scaling Set number of repetitions to 3 number of soil layers involved to 1 and supply the three scaling factors 0 45 1 00 and 2 50 Execute a simulation d Verify results Check that the second simulation indeed corresponds to the reference simulation E
142. generated at regular intervals and additionally at irregular output dates which must be specified explicitly The day counter signalling the end of an output interval may be reset each sequential sub run or just proceed 4 2 3 Section 3 Meteorological data The variable METFIL is the name of file with values of daily meteorological data and reference evapotranspiration data The content of the file is discussed in paragraph 4 3 The name of the file should maximally be 7 characters long as it functions as the first part of the name of related meteo data files The file extensions are derived from the three last digits of a year number An example is a file with the name Hupsel 998 contains meteo data from station Hupsel and year 1998 Note that internally SWAP calculates with actual year numbers 4 digits so that no millennium problem will occur Latitude and altitude of the meteo station are used in the Penman Monteith equation If reference evapotranspiration values are used instead of meteorological data variable SWETR then dummy values for latitude and altitude should be given The variable SWETR indicates whether SWAP should calculate potential evapotranspiration rates from daily meteorological data using the Penman Monteith equation or from daily reference evapotranspiration values In addition to daily rainfall data in the meteo files detailed short timestep rainfall data may be specified in a separate data file The variable SWRA
143. han under low atmospheric demand SWAP assumes a linear relationship between the potential transpiration rate and the threshold pressure head HLIM3 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 49 4 10 8 Section 8 Salt stress Reduction of water uptake due to salt stress needs input of a maximum salt tolerance value EC value below which no salt stress occurs and the slope of the EC and root water uptake reduction curve see Par 2 3 Van Dam et al 1997 4 10 9 Section 9 Interception The precipitation interception coefficient is used to calculate the amount of interception with the Braden 1985 concept At increasing precipitation amounts the interception asymptotically reaches the value COFAB LAI cm where LAI is the leaf area index Note If the soil cover fraction SC is used as input par 4 10 3 then LAI for the interception calculations will be derived from SC according to Van Dam et al 1997 page 75 as LAI SC 3 4 10 10 Section 10 Root density distribution and root growth The user may enter up to 11 data pairs to define the relative root density distribution as a function of the relative rooting depth Any unit for the root density can be used SWAP will normalise the root density distribution such that the integral of root density times depth over the rootzone equals one Root growth is calculated rather straightforward The user needs to define the initial rooting depth the maximum daily increase and the maximum roo
144. he potential transpiration rate below which the actual transpiration rate should fall before initiating an irrigation 2 Allowable depletion of readily available water This parameter determines the depletable fraction 0 1 R of the amount of water in the soil profile between h 100 cm field capacity and the point at which water uptake is reduced hs Fig 2 2 of Van Dam et al 1997 before irrigation should be started The point of reduced water uptake depends on the atmospheric demand These parameters are crop specific and should be specified for each crop model in the crop file CRP section Crop water use 3 Allowable depletion of totally available water This parameter determines the depletable fraction 0 1 R of the amount of water in the soil profile between h 100 cm field capacity and the wilting point h4 Fig 2 2 of Van Dam et al 1997 before irrigation should be started The wilting point is crop specific and should be specified for each crop model in the crop file CRP section Crop water use 4 Allowable depletion amount This value determines a predetermined amount of water 0 500 mm R which can be extracted below h 100 cm field capacity before irrigation should be started 5 Critical pressure head or moisture content exceeded In this case irrigation is initiated as soon as a hypothetical sensor in the soil indicates that the pressure head or moisture content drops below a specified value This would be typic
145. he basic drainage routine should suffice The basic drainage routine does allow for simulation of drainage through several drainage levels including channels when drainage and infiltration resistances are selected Note that in file SWAP KEY section 4 and 5 in case of drainage the user should already have chosen either the basic or the extended drainage routine 4 13 1 Section 1 Method Three methods are available to establish the drainage flux 1 Tabular Qgrain gwl relationship using a table with flux groundwater level data pairs 2 Calculated drainage using the formulas of Hooghoudt and Ernst 3 Linear Qdgrain gwl relationship which is calculated using given drainage infiltration resistance for one or more different levels SWAP allows for both drainage and sub irrigation through the same system Prior to calculating the drainage or sub irrigation rate it is determined whether the flow situation involves drainage sub irrigation or neither No drainage or sub irrigation will occur if both the groundwater level and the surface water level are below the drainage base Drainage will occur if the following two conditions are met e the groundwater level is higher than the channel bed level e the groundwater level is higher than the surface water level Sub irrigation can only occur if the following two conditions are met e the surface water level is higher than the channel bed level e the surface water level is higher than the groundw
146. he top layer Kniop Using the relaxation method Ernst 1962 distinguished the following situations Khnbot Khtop lt 0 1 gt Gar 1 0 1 lt Knbot Kniop gt 50 gt Gar follows from Table 2 gwi hop Kvtop gt fine layer hbot Kvbot gt coarse layer case 5 Fig 5 Five field drainage situations considered in SWAP after Ritzema 1994 The hydraulic head is defined positive upward with y 0 at the soil surface Table 2 Gy as obtained by the relaxation method Ernst 1962 Khbot Khtop Dbot Drop 1 2 4 8 16 32 1 2 0 3 0 5 0 9 0 15 0 30 0 2 2 4 3 2 4 6 6 2 8 0 10 0 3 2 6 3 3 4 5 9 9 6 8 8 0 5 2 8 3 5 4 4 4 8 5 6 6 2 10 3 2 3 6 4 2 4 5 4 8 5 0 20 3 6 3 7 4 0 4 2 4 4 4 6 50 3 8 4 0 4 0 4 0 4 2 4 6 Dbot is thickness of bottom layer Dip is thickness of top layer For more information see paragraph 8 4 in Van Dam et al 1997 The drain characteristics which need to be specified are the same for all 5 different drainage situations and are rather self explanatory The value for the entry resistance 0 1000 d R can be obtained analogous to the resistance value of an aquitard by dividing the wet perimeter of the channel walls by the hydraulic conductivity If the hydraulic conductivity does not differ substantially from the conductivity of the surrounding subsoil the numerical value of the entry resistance will become relatively small 62 SC DLO TECHNICAL DOCUMENT 53 DOC 1
147. hich should be simulated Optional output files Daily meteorological data yyy Radiation temperature vapour pressure wind speed rainfall and or reference evapotranspiration Detailed rainfall r yyy Actual rainfall intensities Fixed irrigation irg Amount and quality of prescribed irrigation applications Calculated irrigation cap Type of irrigation Irrigation timing criteria Irrigation depth criteria Crop calendar cal Crop data input file Calculated irrigation input file Crop emergence and harvest Start irrigation scheduling Detailed crop growth crp Crop height Crop development Initial values Green surface area Assimilation Assimilates conversion into biomass Maintenance respiration Dry matter partitioning Death rates Crop water use Salt stress Interception Root growth and density distribution Simple crop growth crp Crop development Light extinction Leaf area index Soil cover fraction Crop height Rooting depth Yield response Crop water use OC 11999 Detailed crop growth cr Development stage Leaf area index Crop height Rooting depth Cumulative relative transpiration during 0 2 DVS Cumulative relative transpiration during 1 2 DVS Cumulative potential and actual weight of dry matter Cumulative potential and actual weight of storage organ Simple crop growth cr Development stage Leaf area index Crop height Rooting depth Cumulative relative t
148. hould also specify the drain spacing in the drainage file see Par or 4 14 4 13 4 11 11 Section 11 Initial moisture condition The user can define two types of initial moisture conditions 1 The first possibility is to define nodal pressure heads for each compartment This option is useful if the simulated situation starts from non equilibrium or if no groundwater table is simulated Note that initial pressure heads should be entered in cm where negative numbers indicate unsaturated conditions Unlike water contents soil water pressure heads are continuous with depth 2 The second possibility is to define the initial moisture conditions as an equilibrium profile with the groundwater table In this case the nodal pressure at the groundwater table equals zero and the nodal pressure decreases linearly with height towards the soil surface In this case the initial groundwater level needs to be specified Note that the value specified should be negative if the groundwater level is below the soil surface 58 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 AA koX CK Section 8 Preferential flow due to soil volumes with immobile water SWMOBI 0 Switch preferential flow due to immobile water Y 1 N 0 If SWMOBI 1 sp
149. ia and parameters Comment area Section 1 General ISUAS 1 Switch type of irrigation method during scheduling phase 0 sprinkling irrigation 4 1 surface irrigation CIRRS 0 0 solute concentration of scheduled irrig water 0 100 mg cm3 R
150. in drying curve therefore the variable SWHYST must be 2 Next we need to specify the a parameter of the Mualem Van Genuchten function to calculate the main wetting curve see Par 2 2 3 Van Dam 1997 This parameter should be specified in both soil files Sandt sol and Sands sol As a rule of the thumb take ay 2 06 You may verify the values of these parameters file sol section 3 COFGEN4 and COFGEN8 but you don t need to change these values as they have defined already 2 Goto Soil Profile description Load file Hupsel swa At page 3 select hysteresis with initial condition drying As we start the simulation in a wet period in winter we should start from the main drying curve Next we need to specify the aw parameter of the Mualem Van Genuchten function to calculate the main wetting curve see Par 2 2 3 Van Dam 1997 Goto Soil layer hydraulic properties Load file Sandt sol As a rule of the thumb take the parameter aloha main wetting equal to twice the value of aloha main drying Do the same for the second soil layer Sands sol c Execute a simulation d Verity results Analyse the effect of hysteresis on transpiration evaporation drainage and groundwater levels at 31 March and 30 September Answer Fluxes No Hyst With Hyst Unit Potential transpiration 29 6 29 6 cm year Actual transpiration 26 6 26 6 cm year Potential evaporation 35 0 35 0 cm year Actual evaporation 14 4 14 4 cm year Draina
151. ing the root water extraction function The soil water potential stress relationship as depicted in fig 2 2 of Van Dam et al 1997 is used to calculate the water stress of the crop For this relationship the user should specify the upper and lower limits of the root water extraction function the Penman Monteith equation is used the user needs to supply the minimum canopy resistance RSC SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 137 Under high atmospheric demand transpiration might decrease earlier than under low atmospheric demand SWAP assumes a linear relationship between the potential transpiration rate and the threshold pressure head HLIMS 4 8 11 Section 11 Salt stress Reduction of water uptake due to salt stress needs input of a maximum salt tolerance value EC value below which no salt stress occurs and the slope of the EC and root water uptake reduction curve see Par 2 3 of Van Dam et al 1997 4 8 12 Section 12 Interception The precipitation interception coefficient is used to calculate the amount of interception with the Braden 1985 concept At increasing precipitation amounts the interception asymptotically reaches the value COFAB LAI cm where LAI is the leaf area index 4 8 13 Section 13 Root density distribution and root growth The user may enter up to 15 data pairs to define the relative root density distribution as a function of the relative rooting depth Any unit for the root density can be used
152. ingen pp 189 Groenendijk P and J G Kroes 1998 Modelling the nitrogen and phosphorus leaching to groundwater and surface water ANIMO 3 5 Report 144 DLO Winand Staring Centre Wageningen In prep Hijmans R J I M Guiking Lens and C A van Diepen 1994 User s guide for the WOFOST 6 0 crop growth simulation model Technical Document 12 Winand Staring Centre Wageningen The Netherlands 144 p Jansen M J W and J C M Withagen In press USAGE Uncertainty and sensitivity analysis in a Genstat environment Centre for Biometry Wageningen Kroes J G and J Roelsma 1998 ANIMO 3 5 User s Guide for the ANIMO version 3 5 nutrient leaching model Technical Document 46 Winand Staring Centre Wageningen The Netherlands 98 p Mualem Y 1976 A new model for predicting the hydraulic conductivity of unsaturated porous media Water Resour Res 12 513 522 Raes D H Lemmens P van Aelst M vanden Bulcke and M Smith 1988 5 Reference Manual Laboratory of land management faculty of agricultural sciences Katholieke Universiteit Leuven Belgium Ritzema H P 1994 Subsurface flow to drains In Drainage principles and applicatoins H P Ritzema Ed in chief ILRI publication 16 second editions Wageningen p 263 304 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 1103 Scott P S G J Farquhar and N Kouwen 1983 Hysteretic effects on net infiltration In Advances in infiltration American Society of Agric
153. ion 2 Soil evaporation Section 3 Time discretization of Richards equation Section 4 Spatial discretization Section 5 Soil hydraulic functions and maximum rooting depth Section 6 Hysteresis of soil water retention function Section 7 Similar media scaling of soil hydraulic functions Section 8 Preferential flow due to immobile water Section 9 Preferential flow due to soil cracks 4 11 10 Section 10 Vertical distribution of drainage flux 4 11 11 Section 11 Initial moisture condition 4 12 Soil hydraulic functions sol 4 13 Basic drainage drb OC 1 1999 4 8 13 4 9 1 4 9 2 4 9 3 4 9 4 4 9 5 4 9 6 4 9 7 4 9 8 4 9 9 4 9 10 4 9 11 4 10 2 4 10 3 4 10 4 4 10 5 4 10 6 4 10 7 4 10 8 4 10 9 4 11 1 4 11 2 4 11 3 4 11 4 4 11 5 4 11 6 4 11 7 4 11 8 4 11 9 4 9 4 10 4 11 4 13 1 Section 1 Method 61 4 13 2 Section 2 Table of drainage flux groundwater relation 61 4 13 3 Section 3 Drainage formula of Hooghoudt or Ernst 61 4 13 4 Section 4 Drainage and infiltration resistance 63 4 14 Extended Drainage dre 67 4 14 1 General 67 4 14 2 Section 1 drainage characteristics 67 4 14 3 Section 2 surface water system 69 4 15 Bottom boundary conditions bbc 5 4 16 Heat flow hea 78 4 16 1 Section 2 Analytical method 78 4 16 2 Section 3 Numerical method 78 4 17 Solute transport slt 00 4 17 1 Section 1 Top boundary and initial condition 80 4 17 2 Section 2 Diffusion dispersio
154. ion 6 Yield response The yield response factor KY determines at each growing stage the relationship between the relative yield and the relative transpiration defined as the ratio of the actual over the potential transpiration In case of a linear relation between the relative crop yield and the relative transpiration or when no information is available for the yield response factor as a function of DVS specify KY 1 for 0 gt DVS gt 2 4 10 7 Section 7 Crop water use Both the water and the salinity stress will limit the potential transpiration of the crop SWAP assumes that the reduction factors due to water and salinity stress are multiplicative The user should enter the pressure heads defining the root water extraction function The soil water potential stress relationship as depicted in fig 2 2 of Van Dam et al 1997 5 used to calculate the water stress of the crop For this relationship the user should specify the upper and lower limits of the root water extraction function The ratio of potential crop evapotranspiration rate to reference evapotranspiration rate under full soil cover conditions needs to be entered if the user wants to use ETref values instead of the Penman Monteith equation This value is equal to the crop factor for full soil cover the Penman Monteith equation is used the user needs to supply the minimum canopy resistance RSC Under high atmospheric demand transpiration might decrease earlier t
155. ion of dev stage 0 2 R Tf SWCF 2 list crop height 0 1000 cm R as function of dev stage 0 2 R DVS CF or CH maximum 36 records CFTB 0 0 1 0 0 3 15 0 D 5 40 0 0 7 140 0 0 170 0 1 4 180 0 2 0 0 End of table RA KKK KKK KKK KK KK CK KK KKK KK KKK KKK KK KKK KK KK KK KKK KK KKK KK KKK KK KKK KKK KK KKK KK KKK KKK KK KKK KKK KKK KKK KKK KKK KKK KKK KK KKK KKK KKK KK KKK KKK KK KKK KKK KK KKK KK KKK KK KKK KKK Section 5 rooting depth List rooting depth 0 1000 cm R as a function of development stage 0 2 R DVS RD maximum 36 records RDTB 0 00 5 00 0 30 20 00 0 50 50 00 0 70 80 00 1 00 90 00 2 00 100 00 End of table Ck CK C CK CC CC CC C CC CC CK CK RA Section 6 yie
156. ions Answer Reduction at too wet conditions Yes No Unit Potential transpiration 29 6 29 6 cm year Actual transpiration 26 6 29 6 cm year By excluding the stress due to wet conditions the actual transpiration becomes equal to the potential transpiration Probably stress due to wetness occurs and the drains are too high or the spacing is too wide for this particular year 6 2 11 2 Increasing drain depth a Initialise with reference situation described in par 6 1 execute INITIAL BAT b oe input Change in the crop file Hupsel drb section 3 the variable ZBOTDR decrease the drain level ZBOTDR from 80 0 cm to 100 0 cm Change in the file Hupsel swa section 11 the initial groundwater level GWLI from 75 to 95 cm 2 Goto Drainage basic and load file Hupsel swa Decrease the drain level from 80 0 cm to 100 0 cm Goto Soil profile description and load file Hupsel swa Decrease the initial groundwater level from 75 to 95 cm c Execute a simulation d Verify results Compare the transpiration evaporation drainage and groundwater levels for the simulations with both drain depths SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 1101 Unit cm year cm year cm year cm year cm year cm cm 100 0 29 6 28 35 0 14 4 19 4 90 3 144 4 0 97 80 0 29 6 26 6 35 0 14 4 21 4 0 131 5 0 90 Answer Drain depth cm Potential transpiration Actual transpiration Potential evaporatio
157. irrigation scheduling Irrig cap and set start date of irrigation at 1 of May Goto Irrigations scheduled irrigations Load file Irrig cap Verify no changes required at section Timing Criteria the Ratio for allowable Daily Stress Ta Tp 0 95 during the entire growing period Also verify at section Depth Criteria the irrigation depth criterium which must be Back to Field Capacity without under or over irrigation b Execute a simulation 6 Verify results Analyse irrigation transpiration evaporation drainage and crop yield for the years 2000 and 2001 Answer Fluxes 2000 2001 Unit Irrigation 14 0 27 8 cm year Potential transpiration 30 7 30 8 cm year Actual transpiration 30 5 30 3 cm year Potential evaporation 35 0 34 9 cm year Actual evaporation 6 5 5 9 cm year Drainage 0 9 0 0 cm year Crop growth 2000 2001 Unit Relative yield 0 99 0 99 In the second year almost double the amount of irrigation water is needed due to the decrease of water storage in the soil profile The used irrigation criterium increases the relative crop yield to 0 99 in both years If water has to be saved a more stringent irrigation criterium can be considered 6 2 3 Crop type In this exercise the water balance for grassland instead of the maize crop will be simulated using the simple crop growth model a Initialise with reference situation described in par 6 1 execute INITIAL BAT b Change input 1 In the crop calendar file Year8
158. l of phase IPHASE max value 500 0 cm below soil surface R ACRET critical pressure head max value at HDEPTH see above for allowing surface water level 1000 0 cm neg R critical unsaturated volume min value for 1 7 surface water level 0 20 cm R Notes 1 The zero s for the criteria on the first record are in fact i dummy s because under all circumstances the scheme will set the surface water level at least to wlsman imper 1 2 The lowest level of the scheme must still be above the deepest channel bottom of the secondary surface water system IMPER IPHASE WLSMAN GWLCRIT HCRIT VCRIT 2 1 1114 0 0 0 0 0 0 0 2 2 1124 0 80 0 0 0 0 0 2 3 112430 O U0 0 0 0 0 2 4 1154 0 9 0 0 0 0 3 1 LIIS 0 0 0 0 0 0 3 2 1124 0 80 0 0 0 0 0 3 3 1124 0 90 0 0 0 0 0 3 4 1194 00 0 0 0 End of table File hupsel dre extended drainage section4e surface water level is simulated with automatic weir control 74 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 4 15 Bottom boundary conditions bbc The bottom boundary condition in SWAP is considered separate of the drainage or infiltration flu
159. ld response List yield response factor 0 5 R as function of development stage 0 2 R DVS KY maximum 36 records KYTB 0 00 1 00 2 00 1 00 End of table Ck CK CK CC CC C CK CC CCS C CK SCC CK AR koX File maizeS crp simple crop growth sections 3 6 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 151 Section 7 crop water use HLIM1 No water extraction at higher pressure heads 100 100 cm R 0 HLIM2U 30 0 h below which optimum water extr starts for top layer 1000 100 cm R HLIM2L 30 0 h below which optimum water extr starts for sub layer 1000 100 cm R HLIM3H 325 0 h below which water uptake red starts at high Tpot 10000 100 cm R HLIM3L 600 0 h below which water uptake red starts at low Tpot 10000 100 cm R HLIM4 8000 0
160. le of a file with soil water and profile data sections 8 1 4 12 Soil hydraulic functions sol For each soil layer defined in the soil profile the relations between the soil water pressure head the soil moisture content and the unsaturated hydraulic conductivity should be specified SWAP allows either definition of this relationship with a table or with the Mualem van Genuchten analytical function the simulation includes hysteresis of the retention function scaling of the soil hydraulic functions or preferential flow due to immobile water the analytical function should be used SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 9 If the tabular form is chosen for each moisture content 0 1 cm3 cm3 R the corresponding soil water pressure head 1 E10 0 cm R and unsaturated hydraulic conductivity 1 E 15 1000 cm d R needs to be defined The user should start with the lowest water content of which the corresponding pressure head should be lower than 1 0E6 cm Next water content increments of 0 01 should be used until the saturated water content the analytical function option is chosen the parameters of the Mualem van Genuchten equation should be entered The parameter COFGENS describing the a parameter of the main wetting curve of the soil water retention function is only needed in case hysteresis should be si
161. m ext drainage standard 366 maximum oscillation of groundwater level ext drainage standard 1000 0 cm maximum number of management periods ext drainage standard 52 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 121 22 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 0 Fig 3 Main data flow of Swap 2 Bop dens pops Lunge nui 142 ypnod6 das edi egw a see ees LHF sateen cei ue eB ajd Hodxg E abELIES E une t Eqs peneuuejun que aouejeg SUE led HES zos gt 3 14 podra cuba TS Spi tga tae zdao4j3 acu 93 ABEL IE I day ay youd aJmEJsdual 105 apelada 41 ue sos gdoug Nc g4274 nee de Jae A 20 Lini dy o45 page nus ey TEMES ETS 3140 14 Lia ne 3aJmEJaduUual allJHodx3 aBer io hay jeJauag A y EJEP Ajeg uti y y guo nda EJES 55615 uo Ia PslEBP dolg apoy HEN 555 rg deng pajiepp dow Gur Sylb Woes pda ems Mata eag sa1padoJy 201211 des SHIG page nuu 104 Elda daz Jaweed dou AJEpunadq aeg Beug daz amp Jajauue do Sosy rog Jeo papuspe3 35616
162. mal properties SWAP assumes that the solid fraction fraction of the soil that is not water or air is build up out of clay sand and organic matter By supplying the fractions clay and sand the organic matter fraction is known The soil thermal properties are strongly affected by the actual water content 78 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 RS CK CK CK CK CK CK CK Filename Hupsel HEA Contents SWAP 2 0 Heat flow data CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KK RS CK CK CK CK CK CK Comment area Case Water and solute transport in the Hupsel area a catchment in the eastern part of the Netherlands Example of the User s Guide reference situation A set of input data to explore SWAP
163. mbination of the mechanistic and the empirical model In case of grass production however only one crop per year is allowed as the grassland is supposed to be permanent The crop rotation scheme is given in a separate input file The sub model Soil reads spatial discretisation geometry and important soil characteristics Separate input is given for soil physical data bottom boundary conditions surface water system heat flow and solute transport The sub model Irrigation reads from separate input files prescribed irrigation gifts or criteria to simulate irrigation gifts The sub model Timer extracts information from the general input file Swap key and the sub model Soil 3 3 Model extensions For some applications the usual array lengths may be insufficient or the user might wish to decrease some array lengths to use less memory This is possible by changing parameter values that specify certain array lengths in the file PARAM FI and subsequent recompiling the program The array lengths that might be changed are maximum number of years in the simulation period standard 70 maximum number of compartments standard 40 maximum number of horizons standard 5 maximum number of applied irrigations standard 366 maximum number of open water levels basic drainage standard 366 maximum number of water levels primary system ext drainage standard 366 maximum number of water levels secondary syste
164. model system Number of model compartments 1 numnod Number of horizons 1 numlay humlay Number of drainage systems 0 1 2 3 4 nrlevs botcom numlay value must be 0 1 2 3 or 4 The following 4 variables botcom thetawp are given for the horizons 1 numlay 1 Compartment number of the deepest compartment bottom of each horizon layer numnod Volume fraction moisture at Saturation m m 0 0 1 0 thetas numlay Volume fraction moisture at Field Capacity m m 0 0 1 0 thetafc numlay Volume fraction moisture at Wilting point m m 0 0 1 0 thetawp numlay The following variable dz is given for the compartments 1 numnod Thickness of compartments m 0 001 10 E dz numnod 0 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 1123 Mnemonic theta numnod gwl pond tcum iprec lintc levap 0 0 ipeva iptra iruno gwl pond DT Range 0 0 1 0 0 4 gt 0 0 4 gt 0 0 4 gt 0 0 4 gt 0 0 4 gt 0 0 4 gt 0 0 0 0 4 gt 0 0 4 gt 0 0 4 gt 0 0 4 gt 0 0 4 gt Description of variable Unit Initial conditions The following variable theta is given for the compartments 1 numnod Volume fraction moisture inltially present in compartments m m 1 NUMNOD Inltial groundWAterlevel m surface Storage by inltial ponding m surface m surface Dynamic part Time Julian daynumber in hydrological model
165. mulated The option for hysteresis is chosen in file SWA section 6 KKK KKK KK KKK KKK KKK KKK KK KKK KKK KKK KKK KKK KKK KKK KKK KKK KK KK KKK KKK Filename Sandt sol Contents SWAP 2 0 Soil hydraulic functions ko ko ko kk ko ko ko ko ko ko ko KKK KKK E ck ck ck ck ck ck ck ck Ck ck ck c Comment area He c Parameters based on Staring series Wosten et al 1994 ko ko ko ko ko ko ko ck ck ck ck ck ck ck ck ck ck Section 1 Method SWPHYS 1 Switch method to describe soil hydraulic functions Table 0 A 1 Analytical function o
166. n Actual evaporation Drainage Groundwaterlevels 31 March 30 September Crop yield For the year 1980 a change of the drain depth from 80 to 100 cm would increase to actual transpiration from 26 6 to 28 7 cm and increase the relative crop yield from 0 90 to 0 97 Simulations for a range of years are needed to determine the optimal drainage depth for this field 102 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 References Ashby M A J Dolman P Kabat E J Moors and M J Ogink Hendriks 1996 SWAPS version 1 0 Technical reference manual Technical Document 42 DLO Winand Staring Centre Wageningen Belmans C J G Wesseling and R A Feddes 1983 Simulation of the water balance of a cropped soil SWATRE J Hydrol 63 271 286 Berg van den and J J T l Boesten 1998 Pestla 3 2 Description User s Guide and Installation Technical Document 43 DLO Winand Staring Centre Wageningen In prep Boesten J J T l and A M A van der Linden 1991 Modeling the influence of sorption and transformation on pesticide leaching and persistence J Environ Qual 20 425 435 De Vries D A 1975 Heat transfer in soils In Heat and mass transfer in the biosphere I Transfer processes in plant environment De Vries D A and N H Afgan eds Scripts Book Company Washington D C p 5 28 Feddes R A P J Kowalik and H Zaradny 1978 Simulation of field water use and crop yield Simulation Monographs Pudoc Wagen
167. n and solute uptake by roots 80 4 17 3 Section 3 Adsorption 80 4 17 4 Section 4 Decomposition 80 4 17 5 Section 5 Transfer between mobile and immobile water volumes 81 4 17 6 Section 6 Solute residence in the saturated zone 81 Program execution and output 85 5 1 Program execution 85 5 2 Program output 85 Examples 87 6 1 The reference situation 87 6 1 1 Introduction 87 6 1 2 Solute 89 6 1 3 Heat 89 6 1 4 Output of reference situation 89 6 2 Exercises 89 6 2 1 Meteorological year 90 6 2 2 Irrigation 91 6 2 2 1 An imaginary year without rainfall 91 6 2 2 2 Several years without rainfall 92 6 2 2 3 Surface irrigation 93 6 2 3 Crop type 93 6 2 4 Evapotranspiration of partly covered soil 94 6 2 5 Soil texture 95 6 2 6 Hysteresis of retention function 96 6 2 7 Scaling of soil hydraulic functions 96 6 2 8 Root density distribution 97 6 2 9 Bromide breakthrough to surface water 98 6 2 9 1 Breakthrough during a 2 year period 98 6 2 9 2 Influence of an impervious soil layer 99 100 100 101 101 103 105 109 113 123 125 127 6 2 10 Preferential flow 6 2 11 Drainage design 6 2 11 1 Reduction for wet conditions 6 2 11 2 Increasing drain depth References Annexes A Output files of the Hupsel reference case B List of routines of Swap version 2 0 C SWAP list with main variables D Description of the output files afo and aun E Summary of input data F Summary of output data 11999 Summary In an earlier
168. n factor for senescence maximum relative increase in leaf area index ha ha d vertical resistance of semi permeable layer d array with infiltration resistance d relative maintenance respiration rate leaves kg CHO kg d relative maintenance resp rate storage organs kg CH O kg d relative maintenance resp rate roots kg CHO kg d relative maintenance resp rate stems kg CH O kg d cumulative solute amount taken up by the crop mg cm maximum daily increase in rooting depth cm d SC DLO TECHNICAL DOCUMENT 53 DOC 11999 1119 RAPDRA RCC RCS RDC RDCTAB RDI RDM RDRAIN RDRRTB RDS RDTAB RENTRY RER REVA REXIT RFSETB RGRLAI RIMLAY RINFI RML RMO RMR RMS ROTTOT RRI sgnificance threshold daily rainfall cm drainage resistance of surface runoff d minimum water content for potential transformation rate number of current single run runoff flux during current timestep cm d solute storage in saturated groundwater mg cm solute storage in partly filled cracks mg cm initial solute storage in soil profile mg cm solute storage in soil profile mg cm shape factor of groundwater limit of void ratio at zero water content fitting parameter shrinkage characteristic fitting parameter shrinkage characteristic sine of solar elevation degrees seasonal offset of sine of solar height AFGE
169. n into stems 0 1 kg kg R ck ck ck Ck CK ck ck ck ck ck ck ck ko ko ko ko ko ko ko ko ko ko ko ck ck ck ck ck Ck Ck ck ck ck ck ck ko ko ko ko ko ko ko ko ko ko Section 5 Maintenance respiration Q10 2 0 Rel increase of respiration rate with temperature 0 5 10 C R RML 0 030 Rel maintenance respiration rate of leaves 0 1 kgCH20 kg d R RMR 0 015 Rel maintenance respiration rate of roots 0 1 kgCH20 kg d R RMS 0 015 Rel maintenance respiration rate of stems 0 1 kgCH20 kg d R List reduction factor of senescenc R as function of time 0 366 d R Ei TIME RFSE maximum 15 records RFSETB Ta 1 00 366 0 1 00 End of table AR Kk C SKK CC CC KC File grass crp sections 2 5 SC DLO TECHNICAL DOCUMENT 53 DOC 11999 145
170. n of pesticides and no simulation of metabolites SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 117 IC 111999 3 Technical model description 3 1 Model structure A flow chart representing the main structure of the model Swap is given in figure 2 The structure of the program is such that one simulation run may consist of e A simulation period of 70 years sequential sub runs e Upto 70 scenarios of a growing period with a maximum length of one year parallel sub runs e Up to 70 sub runs of a growing period with a maximum length of one year with each sub run its own soil hydraulic functions according to similar media scaling parallel sub runs Simulation and sub run control parameters are initialised at the start of the simulation figure 2 top left The simulation starts for each sub run with the potential crop production of the first day Potential crop production is defined as the total dry matter production of a green crop surface that during its entire growth period is optimally supplied with water and nutrients and grows without interference from weeds pests and diseases The production level is essentially determined by the prevailing weather conditions To get an estimate of the potential production the complete period of the sub run is calculated figure 2 block A Once potential crop production is determined the simulation of water limited crop growth starts with an initialisation of sub models for Timing and Soil Opti
171. nce L4 between drainage canals L4 20 Drain spacing 1 1000 m R ZBOTDR4 90 0 Level of drainage medium bottom 1000 0 cm R SWDTYP4 2 Type of drainage medium 1 Drain tube 2 Open channel In case SWDTYP4 2 specify date day month and channel water level cm negative if below field surface maximum 366 records dd mm LEVEL4 01 01 90 0 31 12 90 0 End of table RS CK CK CK CK CK CK CK RS CK CK CK CK CK CK CK Section 46 Drainage to level 5 DRARES5 0 Drainage resistance 10 1E5 d R INFRES5 100 l Intritration resistance Dels a ER SWALLOS 1 Switch for allowance drainage infiltration 1 Drainage and infiltration are both allowed 2 Drainage is not allowed 3 Infiltration is not allowed In case drainage fluxes should be distributed vertically in the saturated zone SWDIVD 1 in SWA specify the distance L5 between drainage canals L5 20 Drain spacing 1 1000 m R ZBOTDR5 90 0 Level of drainage medium bottom 1000 0 cm R SWDTYP5 2 Type of drainage medium 1 Drain tube 2 Open channel In case SWDTYP5 2 specify date day month and channel water level cm negative 15 below field surface maximum 366 records dd mm LEVELS 01 01
172. nce respiration to increase by a factor 2 Respiration is dependent on relative maintenance coefficients of the specific crop organs These coefficients are proportional to the dry weights of the plant organs Senescence will decrease respiration The reduction factor RFSE is crop specific and may depend on crop development stage The user can enter up to 15 data pairs to define this relationship 4 8 8 Section 8 Partitioning The partitioning of the produced structural plant material to the different plant organs is defined by partitioning factors FR FL FS FO which each depend on crop development stage Note that the sum of the partitioning factors for leaves stems and storage organs should equal 1 0 at any development stage see Par 7 8 of Van Dam et al 1997 4 8 9 Section 9 Death rates The user needs to define the death rate due to water and or salinity stress The death rate of the storage organs is considered to be zero The user can specify a death rate of the roots RDRR and stems RDRS as a function of crop development stage The death rate of the leaves is somewhat more complicated see Par 7 9 of Van Dam et al 1997 and was already defined in section 4 4 8 10 Section 10 Crop water use Both the water and the salinity stress will limit the potential transpiration of the crop SWAP assumes that the reduction factors due to water and salinity stress are multiplicative The user should enter the pressure heads defin
173. ndt sol Drainage lateral basic Hupsel drb Drainage extended surface water Hupsel dre Bottom boundary conditions Hupsel bbc Heat Heat flow Hupsel hea Solute Solute transport and transformation Hupsel slt In the input files of each parameter the symbolic name a description and an identification is given The identification between square brackets uses the following convention 1 range recommended minimum and maximum 2 unit 3 data type Integer R Real 4 Ax character string of x positions For example 5000 100 cm R means value between 5000 and 100 with a unit in cm given as a Real 4 data type which means that a dot must be added Swap uses the units day for time cm for length and mg for mass Exceptions are the input of meteorological data see par 4 3 crop data see par 4 8 4 10 drain spacings and weir discharge coefficients in case of surface water management see par 4 14 General rules for the formats of input files are e order of variables is fixed e free format with structure VariableName value e comment in lines is allowed starting with or l SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 123 e blank lines are allowed In the following paragraphs each of the input files will be briefly discussed 4 2 General information Swap key 4 2 1 Section 1 Environment The project name maximum of 8 characters will be used as a generic file name for several input files
174. needs to be entered In the case of a variable length of the crop cycle different temperature sums need to be entered 4 10 2 Section 2 Light extinction The extinction coefficients are needed to calculate the amount of light which reaches the leaves and the soil surface which in turn determines the rate of assimilation and soil evaporation see also Van Dam et al 1997 page 74 These coefficients are not needed if the soil cover fraction is used to partition potential transpiration and potential evaporation ko ko ko ko ko ko ko ko ko KKK KK E ck ck ck ck ck Filename MaizeS CRP Contents SWAP 2 0 Crop data of simple model Comment area Case Water and solute transport in the Hupsel area a catchment in the eastern part of the Netherlands NE No To 52 He c Example of the User s Guide reference situation e E A set of input data to explore SWAP
175. o allows optimization of 100 ISC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 irrigation time and application of irrigation amounts that take into account a certain amount of leaching In this exercise we will just explore whether the drainage depth in the Hupsel reference situation par 6 1 is optimal for the weather conditions in 1980 First we need to determine whether the reduction of maize growth is determined by either too wet or too dry conditions 6 2 11 1 Reduction for wet conditions a Initialise with reference situation described in par 6 1 execute INITIAL BAT b oe input Change in the crop file MaizeS crp section 8 the variables HLIM1 HLIM2U HLIM2L these parameters determine the wet branch of the root water uptake reduction fucntion to 100 cm By specifying this positive value the simulated maize crop will never suffer from too wet conditions 2 Goto Crop data simple model and load file MaizeS crp At page 3 change the pressure head values to 100 cm for start to extract water from the soil start to extract water optimally from the upper soil layer and start to extract water optimally from the lower soil layers In this way the wet branch of the root water uptake reduction function is eliminated and the simulated maize crop will never suffer from too wet conditions c Execute a simulation d Verify results Compare the transpiration for the cases with and without reduction at too wet condit
176. o simulate spatial variability following Miller and Miller 1956 For each defined scaling factor SWAP will run another simulation using the scaled soil hydraulic functions These runs are thus examples of parallel runs If this option is chosen a maximum period of one year can be simulated with SWAP SWAP allows for the definition of 30 different scaling factors implying 30 different sub runs SC DLO TECHNICAL DOCUMENT 53 DOC 01 1999 055 The user should define the number of repetitions or scaling factors and soil layers which should be scaled The soil layers are counted from the soil surface downwards For each repetition the user should specify a scaling factor of which 1 0 means not scaled scaling is chosen by the user the soil hydraulic functions should be defined with the Mualem van Genuchten parameters in the soil hydraulic function files SOL If scaling applies hysteresis of the retention function section 6 or preferential flow due to immobile water section 8 can not be applied AR KKK KK KKK KKK AAA KKK KK KKK KKK KK KKK KK KKK KK KKK KKK KK KKK KKK KKK KKK Section 4 Spatial discretization NUMLAY 2 Number of soil layers 1 5 I NUMNOD 34 number of soil compartments 1 40 I List compartment number at bottom of each soil layer max 5 1 40 I BOTCOM 14 34 List thickness
177. o supply three points of the relationship between moisture ratio v and the void ratio e and SWAP will determine the necessary parameters describing the entire shrinkage characteristic The points which need to be supplied are the void ratio e at v 0 zero water content the moisture ratio at the transition of residual to normal shrinkage v and the structural shrinkage vs See for more detail Fig 5 2 of Van Dam et al 1997 the crack area at the soil surface is calculated the crack area for infiltration might be underestimated due to the sharp water content increase close to the soil surface This would underestimate the amount of infiltration into the cracks To prevent this SWAP allows calculation of the horizontal crack area for infiltration at a certain soil depth Applications show that a depth of 5 cm below soil surface performs well Shrinkage might not occur in an isotropic way meaning that all three dimensions shrink at the same rate This is defined by the geometry factor Rs which equals 3 in case of isotropic shrinkage If only subsidence occurs Rs 1 in case subsidence dominates cracking 1 gt Rs gt 3 in case cracking dominates subsidence Rs gt 3 The diameter of the soil matrix polygon determines the area of the crack walls relative to the surface area The bypass flow rate of the crack storage water which bypasses the soil matrix and directly flows to the drains is calculated similar to linear
178. od 1 January 1981 until 31 December 1981 the output dates must be changed accordingly note that February has 28 days in 1981 c Execute a simulation with SWAP d Verify results In the file Result wba compare rainfall transpiration evaporation drainage and groundwater levels for 31 March 31 July and 30 November between 1980 reference situation from par 6 1 and 1981 Also check bromide amounts leached to surface water in file Result sba Answer Fluxes 1980 1981 Unit Rainfall 66 0 79 9 cm year Potential transpiration 29 6 27 7 cm year Actual transpiration 26 6 26 9 cm year Potential evaporation 35 0 29 9 cm year Actual evaporation 14 4 14 9 cm year Drainage 21 4 33 0 cm year 90 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Groundwaterlevels 1980 1981 31 March 70 0 67 4 cm 31 July 78 5 91 9 cm 30 November 107 5 65 6 cm Leaching bromide to drain 1980 1981 31 July 39 3 60 0 mg cm 31 December 39 5 107 8 mg cm 6 2 2 Irrigation This exercise shows how SWAP can be used to optimize irrigation The exercise consists of three parts 6 2 2 1 an imaginary year without rainfall 6 2 2 2 several years without rainfall 6 2 2 3 surface irrigation Only the first of these 3 exercises must be initialised the other 2 exercises continue with the results of the previous exercise 6 2 2 1 An imaginary year without rainfall An imaginary year 2000 without rainfall will be simulated first a Initialise with refe
179. odel SWAP e For all soil crop combinations the soil and crop evaporation were strongly depending on the function describing the Leaf Area Index LAI e Drainage simulated as lateral discharge is very sensitive to the surface water levels e High groundwater levels are strongly related to surface water levels low groundwater levels depend on a combination of LAI soil physical parameters and surface water levels the average groundwater level is mainly determined by the level in the primary drainage system e At low values for the saturated hydraulic conductivity the model SWAP did not succeed in finishing the simulations within one hour cpu time this occurred for peat at values below 0 1 cm d and for clay at values below 0 06 cm d At these low values the Richards equation could not be solved within the specified cpu time SWAP 2 0 is developed for calculations with daily meteorological input data Exceptions are e g studies with surface water runoff for which the user may provide actual short time rainfall intensities In general model results should be analysed on a daily base For many cases this will be sufficient for analyses using more detailed and complete meteorological data other models such as SWAPS Ashby et al 1996 are recommended Other limitations of this version of SWAP are e no simulation of regional groundwater hydrology e no interaction between crop growth and nutrient availability e no non equilibrium sorptio
180. onally the Irrigation sub model is initialised Next the simulation starts the day at 00 00 hour with the intake of meteorological data after which the sub model Soil solves the discretized equations for water flow solute transport and heat flow figure 2 block B These calculations are performed with a reduced timestep which will be decreased maintained or increased according to numerical conditions for the solution of water flow and solute transport equations see Van Dam et al 1997 par 2 4 and par 3 3 Within the sub model Soil the top lateral and bottom boundary conditions are determined first after which the sink term of root water extraction is calculated With boundary conditions and sink terms known the Richards equation is solved resulting in values for pressure heads and moisture contents for the next timestep Soil temperatures are then determined by solving the heat flow equation Parameters for hysteresis are updated and the daily water fluxes are integrated If interaction with the surface water system is required extended drainage the various surface water flows are calculated Also during each time step the solute transport equation is solved using the actual soil water fluxes The sub model Soil is called for each timestep until the end of the day Once the end of a day is reached and the calculations with the sub model Soil are finished the actual crop growth rates are determined and its corresponding state variables a
181. ontains immobile water type of implicit scheme used switch indicating type of weir discharge relationship options for reduction of soil evaporation switch for similar media scaling switch indicating surface water is simulated or input switch for simulation of solute transport switch for specification of the surface water system RSIGNI RSRO RTHETA RUNNR RUNOTS S SAMAQ SAMCRA SAMINI SAMPRO SHAPE SHRINA SHRINB SHRINC SINB SINLD SLATB SLOPFM SLOPFM SPA SPAN SQBOT SQDRA SQRAP SQSUR SQTOP SSA STRING STTAB SWAFO SWAIR SWALLO SWANAF SWATE SWAUN SWBOTB SWDRA SWDRF SWDTYP SWETR SWHYST SWINCO SWMAN SWMOBI SWNUMS SWQHR SWREDU SWSCAL SWSEC SWSOLU SWSRF 120 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 switch for output of water balance surface water reservoir switch indicating presence of temperature data time since start of the agricultural year d name of the table array with side slope of channel dh dw amplitude of annual temperature wave at soil surface C minimum head difference for change scanning curve cm average day temperature C lower threshold temperature for ageing of leaves C time since begin of simulation run d initial total crop dry weight kg ha array with temperature at surface and nodal points C array with initial values for TEMP C array with volumetric moisture content of
182. oscillation cm OUTPER counter OVERFL flag for overflow of automatic weir OWLTAB array with time amp water level in ditch cm relation P Pl lower limit 01 the range P2 upper limit of the range PARDIF diffuse irradiance on a horizontal plane J 8 PARDIR direct irradiance on a horizontal plane J m s PercentClay percentage of clay in dry soil PercentSand percentage of sand in dry soil PERDL maximum relative death rate of leaves due to water stress d PERIOD Output interval days PEVA potential soil evaporation rate cm d PFI array with pF values first data point one for each layer PF2 array with pF values second data point one for each layer 118 SC DLO TECHNICAL DOCUMENT 53 DOC 11999 thickness of ponding water layer cm ponding layer during previous timestep cm maximum thickness of ponding layer cm porosity of aquifer potential transpiration rate cm 0 array with flow depth through top of compartment cm relative increase in respiration rate per 10 C temperature increase flux through bottom boundary of the profile cm d upward AFGEN table with combinations of daynumber T and lower boundary flux cm d infiltration rate from cracks into soil matrix cm d array with flux per node to from each drainage level cm d array with drainage infiltration flux per dr level cm d
183. p 4 6 1 Section 1 General 4 6 2 Section 2 Irrigation time criteria 4 6 3 Section 3 Irrigation depth criteria Crop rotation cal Detailed crop growth crp 4 8 1 Section 1 Crop factor or crop height 4 8 2 Section 2 Crop development 4 8 3 Section 3 Initial values 4 8 4 Section 4 Green surface area 4 2 4 4 8 55 55 55 55 57 Section 5 Assimilation Section 6 Conversion of assimilates into biomass Section 7 Maintenance respiration Section 8 Partitioning Section 9 Death rates Section 10 Crop water use Section 11 Salt stress Section 12 Interception Section 13 Root density distribution and root growth Detailed grass growth crp Section 1 Initial values Section 2 Green surface area Section 3 Assimilation Section 4 Conversion of assimilates into biomass Section 5 Maintenance respiration Section 6 Partitioning Section 7 Death rates Section 8 Crop water use Section 9 Salt stress Section 10 Interception Section 11 Root density distribution and root growth Simple crop growth crp 4 10 1 Section 1 Crop development Section 2 Light extinction Sections 3 LAI or soil cover Section 4 Crop factor or crop height Section 5 Rooting depth Section 6 Yield response Section 7 Crop water use Section 8 Salt stress Section 9 Interception 4 10 10 Section 10 Root density distribution and root growth Soil water and profile swa Section 1 Ponding Sect
184. p factor or crop height SWCF 1 choice between crop factor 1 or crop height 2 If SWCF If SWCF lg LSt Crop factor El as function of dev stage 0 2 list crop height 0 1000 cm R as function of dev stage CF or CH maximum 15 records End of Table XX X A AAA CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK CK CK CK CK CK CK File wheatd crop detailed crop growth section 1 4 8 2 Section 2 Crop development Growth simulation is started at the emergence date specified by the user in the crop calendar file A crop passes through the successive phenological stages from 0 to 2 depending on the development rate The development rate can depend either on temperature or daylength or both In modern cultivars the day length can generally be ignored if an appropriate temperature sum is chosen For more information the user should check Van Dam et al 1997 par 7 2 temperature is chosen appropriate temperature sums should be defined which will determine the development stage of the crop If daylength is chosen appropriate optimum and threshold daylengths should be defined to determine the reduction factor for the development rate of the crop If the combination option is chosen the user should specify SC DLO TECHNICAL DOCUMENT 53 DOC 11999 135 both the temperature and the da
185. par 4 10 with reference evapotranspiration as input par 4 3 For such a case the given reference evapotranspiration may be corrected for periods where the crop is absent or small One value can be given within the ranges 0 5 and 1 5 SWAP calculates actual soil evaporation using the soil hydraulic functions in case of a dry soil In case of a wet soil actual evaporation equals potential evaporation To calculate the actual evaporation accurately the thickness of the top compartment should not be too large see for detailed information Van Dam et al 1997 par 2 2 and 6 8 The manual suggests a thickness of 1 cm near the soil surface Since the soil evaporation could be overestimated using ordinary soil hydraulic functions SWAP allows the use of two alternative empirical functions Since these functions are empirical the parameters are soil and location specific and will need to be determined by the user SWAP will determine the actual evaporation rate by taking the minimum value of Emax from soil hydraulic functions E potential from meteo data and the evaporation rates according to the empirical functions if selected by the user 4 11 3 Section 3 Time discretization of Richards equation To solve the numerical scheme accurately and efficiently the user should define minimum and maximum time steps The time steps are defined as fractions of a day The program will look for the optimal time step between the defined limits taking
186. pre anthesis development IEVAP cumulative actual soil evaporation cm IINTC cumulative interception cm 116 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 length of the table array with time T that management period ends d index for current management period array with wetting curve 1 or drying curve 1 indicators array with infiltration resistance per level d array with relative location of upper boundary of compartment array with relative location of lower boundary of compartment array with cumulative flow depth through top of compartment cm array with cumulative drainage flow depth per level per node cm array with cumulative root extraction volume per node cm length of water level adjustment period d cumulative intermediate potential soil evaporation cm position of the drain tubes cumulative intermediate precipitation cm cumulative intermediate potential transpiration cm cumulative intermediate flow depth through bottom of profile cm cumulative intermediate flow from cracks into matrix cm cumulative intermediate total drainage flux cm depth cm cumulative intermediate rapid drainage flow cumulative intermediate whole root zone root water extraction cm number of the current single simulation run cumulative surface runoff cm number of the soil layer involved in scaling sequential 1 or par
187. py resistance 0 1000 s m R ADCRH 5 Level of high atmospheric demand 0 5 cm d R ADCRL 0 1 Level of low atmospheric demand 0 5 cm d RI Ck CK CK CC CC CK CC CK CC C CC CC ko o Ck CK RA Section 11 Salt stress ECMAX 2 0 ECsat level at which salt stress starts 0 20 dS m R ECSLOP 0 0 Decline of rootwater uptake above ECMAX 0 40 dS m R Ck CK Ck CK CC CC CK CK CC CK SCC SCC ko o
188. r DRE Which type to be specified if any is one of the run options in section 5 e BBCFIL input file with the bottom boundary condition BBC e OUTFIL generic name of output files for this year 4 2 5 Section 5 Processes which should be considered For the simulation of lateral drainage three options are available e no simulation of lateral drainage e simulation with the basic drainage routine lateral drainage to maximally 5 drainage levels no simulation of the surface water balance e simulation with the extended drainage routine lateral drainage to maximally 5 drainage levels taking into account simulation of the surface water balance The possibility to simulate solute and heat transport can be switched on or off 4 2 6 Section 6 Optional output files Under output options the user can specify whether additional output files of the extended drainage routine and the profile file for each output day vertical profiles of soil water content solute concentration soil temperature soil water flux and solute flux must be produced 4 2 7 Section 7 Optional output files for water quality models This section contains switches that arrange output to files which are commonly used by water quality models like PESTLA Berg and Boesten 1998 and ANIMO Kroes and Roelsma 1998 Options can be switched on and off and names for the related output files can be specified 26 SC DLO TECHNICAL DOCUMENT 53 DOC 1 199
189. r Jan 1 1 with top hydraulic head 1 366 d I AQPER 5 Period hydraulic head sinus wave 1 366 d I Ck CK KK KKK KK KKK KKK KK KKK KKK KKK KKK KKK KKK KKK KKK KK KKK KK KKK KKK A SWOPT4 0 Switch calc bottom flux as function of groundw level Y 1 N 0 If SWOPT4 1 specify of q A exp Bh relation COFQHA Coefficient A 100 100 cm d R COFQHB Coefficient B 1 1 cm R SWOPT5 0 Switch use pressure head of bottom compartment Y 1 N 0 If SWOPT5 1 specify date day month and bottom compartment pressure head cm negative if unsaturated maximum 366 records d5 m5 GWlevel 1 50 0 31 12 20 0 End of table koX KK KKK KK KKK KK KKK KKK KKK KK KKK KKK KK KK KKK KKK KKK KKK KK KK KKK KKK KKK X SWOPT6 1 Switch bottom flux equals zero Y 1 N 0 SWOPT7 0 Switch free drainage of soil profile Y 1 N 0 SWOPT8 0 Switch free outflow at soil air interface Y 1
190. r interception and actual transpiration and a smaller actual evaporation and drainage 6 2 4 Evapotranspiration of partly covered soil The potential evapotranspiration demand as exerted by the atmosphere has to be divided into potential transpiration and potential evaporation see Par 6 6 Van Dam 1997 This division can be based on the leaf area index or the soil cover As the reduction of potential transpiration is generally much less than the reduction of potential evaporation the water balance is quite sensitive to the method used to divide potential transpiration and potential evaporation In this exercise we change the method of division and evaluate the effect on the simulated water balance a Initialise with reference situation described in par 6 1 execute INITIAL BAT b Change input 1 Use soil cover data to divide potential evapotranspiration into potential transpiration and potential evaporation Therefore you must change in the crop data file MaizeS crp section 4 the variable SWSC to a value of 1 Verify whether the soil cover data variable SC correspond to data given in par 6 1 table 3 2 Goto Crop data simple model Load file MaizeS crp At page 2 select to use soil cover data to divide potential evapotranspiration into potential transpiration and potential evaporation Supply the soil cover data as specified in par 6 1 table 3 c Execute a simulation Verify results Compare transpiration evaporation
191. r at which the maximum occurs SC DLO TECHNICAL DOCUMENT 53 DOC 11999 175 the period of the sine wave Ad 4 Upward flux calculated as a function of groundwater The exponential relationship was developed for deep sandy areas in the Netherlands so care should be taken when this condition is used in other areas The user should specify the coefficients in the exponential relationship Van Dam et al 1997 refer to Massop and De Wit 1994 and Ernst and Feddes 1979 for examples of these relationships Ad 5 Pressure head of the bottom compartment is given In general this is called a Dirichlet condition The user can specify up to 366 pressure heads 1 E10 1 E5 cm R in the table Ad 6 Zero flux at the bottom of the profile This condition can be used if an impermeable layer exists at the bottom of the profile Ad 7 Free drainage at the bottom of the soil profile This condition applies to soil profiles with deep groundwater levels for which unit gradient of hydraulic head can be assumed at the bottom boundary Mind that the accuracy of the simulated water contents depends to a large extent on the accuracy of the specified unsaturated hydraulic conductivity function Ad 8 Lysimeter with free drainage This option can be used if free outflow at a soil air interface is to be simulated Drainage will only occur if the pressure head in the bottom compartment increases until above zero If the pressure head is negative a no flux boundar
192. r limits of the root water extraction function the Penman Monteith equation is used the user needs to supply the minimum canopy resistance RSC Under high atmospheric demand transpiration might decrease earlier than under low atmospheric demand SWAP assumes a linear relationship between the potential transpiration rate and the threshold pressure head HLIMS 4 9 9 Section 9 Salt stress Reduction of water uptake due to salt stress needs input of a maximum salt tolerance value EC value below which no salt stress occurs and the slope of the EC and root water uptake reduction curve see Par 2 3 of Van Dam et al 1997 4 9 10 Section 10 Interception The precipitation interception coefficient is used to calculate the amount of interception with the Braden 1985 concept At increasing precipitation amounts the interception asymptotically reaches the value COFAB LAI cm where LAI is the leaf area index 4 9 11 Section 11 Root density distribution and root growth The user may enter up to 15 data pairs to define the relative root density distribution as a function of the relative rooting depth Any unit for the root density can be used SWAP will normalise the root density distribution Root growth is calculated rather straightforward The user needs to define the initial rooting depth the maximum daily increase and the maximum rooting depth The daily increase is equal to the maximum daily increase unless too few assimilates
193. ranspiration Cumulative relative crop yield Extended drainage components drf Drainage fluxes of each level Total drainage flux Net runoff Rapid drainage Surface water management 1 swb Groundwater level Weir target level Surface water level Storage in surface water reservoir Sum of drainage runoff and rapid drainage External supply to surface water reservoir Outflow from surface water reservoir Surface water management 2 man Weir type Groundwater level Pressure head for target level Total air volume in soil profile Weir target level Surface water level Surface water outflow Number of target level adjustments Indicator weir overflow Weir crest level Final pressure heads Hfinal dat Final pressure heads Log file SWAP207 log Error mess Annex F Summary of output data Total water and solute balance bal Final and initial water and solute storage Water balance components Solute balance components Incremental water balance components inc Gross rainfall Gross irrigation Interception Runoff Potential and actual transpiration Potential and actual evaporation Net drainage Net bottom flux Cumulative water balance components wba Gross and net rainfall Gross and net irrigation Runoff Potential and actual transpiration Potential and actual evaporation Net lateral flux drainage Net bottom flux Change water storage in profile Groundwater level Water balance error
194. rds RDRRTB 1 0 0 00 366 0 0 00 End of table List relative death rates of stems kg kg d as function of time 0 366 d R TIME RDRS maximum 15 records RDRSTB 1 0 0 00 366 0 0 00 End of table koX KKK KK KKK KK KKK KK KKK KKK KK KKK KKK KKK KKK KK KKK KKK KK KKK KKK KK KK KKK KKK koX KKK KK KKK KKK KKK KKK KKK KKK KKK KKK KKK KK KKK KKK KK KKK KKK KK KK KKK KKK KKK KK KKK CK Section 8 Crop water use HLIM1 10 HLIM2U 25 2D No water extraction at higher pressure heads 100 100 cm R h below which optimum water extr starts for top layer 1000 100 cm R h below which optimum water extr starts for sub layer 1000 100 cm R h below which water uptake red starts at high Tpot 10000 100 cm R HLIM3L 800 h below which water uptake red starts at low 700 10000 100 cm R HLIM4 8000 No water extraction at lower pressure heads 16000 100 cm R RSC 70 0 Minimum canopy resistance 0 1000 s m R ADCRH 0 5 Level of high atmospheric demand 0 5 cm d R ADCRL 0 1 Level of low atmospheric demand 0 5 cm d RI
195. re integrated After updates of some parameters the next day of simulations starts Once the last day of a simulation sub run is reached the sub model Soil is terminated and once the end of the last sub run is reached the complete simulation ends SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 119 Initialize timer Start sub run Start of day 00 00 h Initialize crop growth Read meteorological data Crop growth rates and integration of state ES End of day 24 00 h Last day of sub run Bottom boundary Lateral boundary conditions Crack flow Top boundary conditions Root extraction rate Pressure heads and moisture Soil temperatures Hysteresis Integrate state variables Surface water system Solute concentrations and mass n End of simulation Read simulation control and soil characteristics Start simulation sub run 1 sub run simulates maximum period of 1 year Simulation of potential crop Start simulation of water limited crop Initialize timer Initialize soil and irrigation part1 sub Start of day 00 00 h Initialize crop and irrigation part2 sub Determine irrigation part3 Read meteorological data Soil sub model for one timestep Calculate dt en t N End of day 24 00 h Crop growth rates and integration of state 2 Terminate irrigation sub Update flags switches and Last day a of sub run Terminate soil sub model Last sub run of simulation
196. rence situation described in par 6 1 execute INITIAL BAT b Change input 1 Inthe file Swap key section 2 the simulation period must be changed to 1 January 2000 31 December 2000 and the output dates must be changed accordingly be aware that the year 2000 is a leap year 2 Load SwapGui key on directory c swap examples exercise In section Timing the simulation period must be changed to 1 January 2000 31 December 2000 and the output dates must be changed accordingly be aware that the year 2000 is a leap year c Execute a simulation d Verify results In the output file Result wba compare transpiration evaporation drainage and groundwater levels for 31 March 31 July and 30 September between 1980 and 2000 Also check bromide amounts leached to surface water in the output file Result sba Answer Fluxes 1980 2000 Unit Potential transpiration 29 6 30 7 cm year Actual transpiration 26 6 27 1 cm year Potential evaporation 35 0 35 0 cm year Actual evaporation 14 4 4 4 cm year Drainage 21 4 0 9 cm year SC DLO TECHNICAL DOCUMENT 53 DOC 11999 1 Groundwaterlevels 1980 2000 Unit 31 March 70 0 87 9 cm 31 July 78 5 136 1 cm 30 September 131 5 174 2 cm Leaching bromide to drain 1980 2000 Unit 31 July 39 3 0 00 mg cm 31 December 39 3 0 00 mg cm Although no rainfall occurred in this year the maize crop is able to transpire 27 1 cm water out of a demand of 30 7 cm The crop survives because of the large initial w
197. rent modelling concepts and simulation techniques Main improvements are accurate numerical solution of the Richards flow equation and incorporation of solute transport heat flow soil heterogeneity detailed crop growth regional drainage at various levels and surface water management The model offers a wide range of possibilities to address both research and practical questions in the field of agriculture water management and environmental protection DLO Winand Staring Centre and Wageningen Agricultural University have developed the computer model SWAP 2 0 in close co operation SC DLO TECHNICAL DOCUMENT 53 DOC 3 1999 1 IC 111999 2 Brief theoretical description The theory of the processes simulated by SWAP 2 0 is extensively described by Van Dam et al 1997 This chapter summarises the most important theoretical concepts which should be known for proper use of the program 2 1 System definition SWAP is a computer model that simulates transport of water solutes and heat in variably saturated top soils The program is designed for integrated modelling of the Soil Atmosphere Plant System figure 1 Transport processes at field scale level and during whole growing seasons are considered System boundaries at the top are defined by the soil surface with or without a crop and the atmospheric conditions The lateral boundary simulates the interaction with surface water systems The bottom boundary is located in the unsaturated zone or
198. rse is defined by certain criteria that are defined in a table This table should be given for each management period the index of the management period the phase of the scheme the water level setting of the automatic weir in phase Osur tar the groundwater level criterium for allowing a weir setting Om max the pressure head criterium for allowing a weir setting Np max the unsaturated volume criterium for allowing a weir setting Vs min CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK KKK RS CK CK CK CK CK Section 2a Specification and control of surface water system SWSRF 2 option for interaction with surface water system 1 1 no interaction with surface water system 2 surf water system is simulated with no separate primary system 3 surf water system is simulated with separate primary system
199. s been specified the defined ground water level in this section determines the initial soil water profile Ad 2 Regional bottom flux is given The user can either use a table to specify the regional bottom flux or use a sine function to generate a regional bottom flux If a sinusoidal bottom flux is defined the user should provide mean 10 10 cm d R amplitude 10 10 cm d R and the day number 1 366 at which the maximum of the sine wave occurs Positive values for the function are an upward flux while negative values are a downward flux Ad 3 Flux from a deep aquifer is calculated In this case pot is calculated from an aquifer below an aquitard Since the shape of the groundwater above the aquitard is important in calculating the average groundwater level the user should specify a shape factor of the phreatic surface and the mean drainage base depth see Fig 2 6 and Par 2 4 3 in Van Dam et al 1997 Possible values for the shape factor are 0 66 parabolic 0 64 sinusoidal 0 79 elliptic and 1 00 no drains flat The bottom flux is calculated using the hydraulic head difference between the phreatic groundwater and the groundwater in the semi confined aquifer and the resistance of the semi confining layer The user should also specify the parameters defining the sine wave in the aquifer similar to condition 2 The user should enter subsequently the amplitude or maximum deviation of the sine wave the daynumbe
200. s crop the reduction factor RFSE can be dependent on the season The user can enter up to 15 data pairs to define the relationship between RFSE and daynumber 4 9 6 Section 6 Partitioning The partitioning of the produced structural plant material to the different plant organs is defined by partitioning factors FR FL FS which each depend on the season i e daynumber Note that the sum of the partitioning factors of leaves and stems should equal 1 0 at any development stage see Par 7 8 of Van Dam et al 1997 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 143 4 9 7 Section 7 Death rates Here the user needs to define the death rate due to water and or salinity stress The user can specify a death rate of the roots RDRR and stems RDRS as a function of the daynumber up to 15 data pairs The death rate of the leaves is somewhat more complicated see paragraph 7 9 of Van Dam et al 1997 and has already partly been in section 2 4 9 8 Section 8 Crop water use Both the water and the salinity stress will limit the potential transpiration of the crop SWAP assumes that the reduction factors due to water and salinity stress are multiplicative The user should enter the pressure heads defining the root water extraction function The soil water potential stress relationship as depicted in fig 2 2 of Van Dam et al 1997 5 used to calculate the water stress of the crop For this relationship the user should specify the upper and lowe
201. simulation is executed by entering the name of the executable SWAP e g sw207_32 exe directly from the command line Indirectly a simulation can be executed by entering the name of a batch file Along with the program a simple batch file is supplied in the directory of the examples The program is protected against extreme incorrect values of input parameters A range check is performed on the upper and lower boundary values of most input parameters Error messages will be written to the screen or to a file called Swap log which will be generated at the same directory from where the program is executed A consistency check of all options and corresponding parameter values however is impossible It is therefore required that users have basic knowledge of the modelled processes 5 2 Program output The program may generate various ASCII output files see figure 3 which can be switch on of by means of variables given at the end of the general input file Swap key The sub model for Soil may produce the following output files Water balance with cumulative data wba Water balance with data for time increments inc Water balance with data cumulative over time and vertical space bal Solute balance sba Soil temperature tep Soil moisture solute and temperature profiles vap Interaction with surface water Extended Drainage drf swb man The sub model for irrigation may generate simula
202. t 2 meter height m s array with allowed dip of surface water level before starting supply cm SC DLO TECHNICAL DOCUMENT 53 DOC 11999 1121 SWSRFO SWTEMP 1 T TABLE TALUDR TAMPLI TAU TAV TBASE TCUM TDWI TEMP TEMPI THETA THETAI THETAR THETAS THETCR THETHI THETIM THETLO THETMI THETOL THETSL ThickComp TIMREF TMEAN TMNFTB TMPFTB TSCF TSUMAM TSUMEA U V VCRIT VOLACT VOLINI VOLMI VOLSAT VTAIR W WCON WETPER WIDTHR WIN WLDIP WLEV surface water level cm WLP surface water level primary system cm WLPTAB AFGEN table with combinations specifying water level in the primary system cm neg as a function of time WLS surface water level secondary system cm WLSBAK arraywith water levels secondary system at past four timesteps cm WLSMAN array with surface water level of phase IPHASE cm WLSTAB AFGEN table with combinations specifying water level in the secondary system cm neg as a function of time WLSTAR target level of surface water cm WSCAP array with surface water supply capacity em d WST current surface water storage cm WSTINI initial surface water storage cm WSTOR surface water storage cm WTOPLAT lateral surface flow into cracks cm X value of the independent variable AFGEN STEPNR parameter to restrict LIMIT Y YEAR year number YEARI year number of first date YEAR2 year number of second da
203. t and depth in the soil profile Details are provided in paragraph 3 3 of Van Dam et al 1997 80 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 The user should specify e potential decomposition rate d e temperature parameter yr used to calculate the reduction factor due to temperature Van Dam et al 1997 page 43 e minimum water content for potential decomposition e exponent of the relation proposed by Walker 1974 to describe reduction of decomposition due to dryness e of each layer a decomposition reduction factor due to depth which can only be derived from field experiments 4 17 5 Section 5 Transfer between mobile and immobile water volumes If preferential flow due to unstable wetting fronts is modelled SWAP uses the two domain mobile immobile model Since the fraction of mobile water has already been specified in file SWA section 8 only the solute exchange rate between the mobile and immobile parts should be specified here d 4 17 6 Section 6 Solute residence in the saturated zone In this section the user may specify parameters to calculate the solute breakthrough to surface water In the saturated zone only linear adsorption and first order decomposition can be considered In case no breakthrough curve should be simulated the user only needs to enter the solute concentration in the aquifer which will be used as a lower boundary condition In case a breakthrough to surface water should b
204. t for the preferential flow if applicable should be defined in file SLT section 5 The mobile fraction of the soil is defined in this section In water repellent soils the mobile soil fraction may depend on the water content of the soil SWAP assumes a linear relationship between log h and the mobile soil fraction The user should specify the log h and the mobile soil fraction FM for two data points to define this linear relationship If the user wants to simulate a situation in which the mobile soil fraction is not dependent on the soil water content of course a constant relationship can be defined Additionally the constant volumetric water content in the immobile fraction should be specified since this value can be substantially different from the water content in the mobile soil fraction preferential flow is selected by the user the soil hydraulic functions should be defined with the Mualem van Genuchten parameters in the soil hydraulic function files SOL If preferential flow applies hysteresis of the retention function section 6 or scaling of the soil hydraulic functions section 7 can not be applied 4 11 9 Section 9 Preferential flow due to soil cracks SWAP employs the clay shrinkage characteristic for the simulation of soil crack formation and water and solute transport in cracks The residual shrinkage stage of the shrinkage characteristic is described by an exponential relationship The user needs t
205. t period a fixed or automatic weir can be simulated The user should provide a water management scheme that specifies the target level for surface water the maximum mean groundwater level the maximum soil water pressure head and the minimum air volume in the soil SWAP will select the highest surface water level for which all criteria are met 2 9 Sensitivity and limitations To gain insight in the sensitivity of the results of the model SWAP to changes on some of its input parameters a global sensitivity analysis was performed with this model by Wesseling and Kroes 1998 Generation of parameter values and the analysis were carried out with the statistical package Usage Jansen and Withagen 1997 for different 16 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 crop soil combinations The analysis was carried out with a range of meteorological years which included average and extreme meteorological data Input parameters were selected that are associated with a number of processes in the SWAP model soil physics evapotranspiration drainage regional hydrology For each input parameter a distribution type its average variance minimum and maximum value were selected using existing databases and expert judgement The analysis focussed on results as cumulative terms of the water balance and groundwater level Some conclusions drawn from this analysis are e Boundary conditions both upper and lower are of crucial importance when applying the m
206. te 7 array with position of nodal points cm negative ZBOTDR array with bottom of drainage medium cm neg ZINTF depth of the interface between the two layers cm ZNCRACK depth where crack area soil surface is calculated cm 122 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Annex 0 Description of the output files afo and aun This annex describes the content of the output files with extension afo and aun The content of both files is identic they only differ in format one file is binary and unformatted aun and the other file is formatted afo The description given in this annex uses the following symbols units as theyu are applied in these files units may differ from those applied in Swap Unit R data are written to a new record DT data type R means Real 4 means Integer 2 Mnemonic the name of the variable as applied in the source code of Swap Description of variable Unit Range R DT Mnemonic Time domain Year when hydrological simulation started 1 1 4 lt E bruny Year when hydrological simulation ended 2 bruny 4 gt 1 eruny Time Julian daynumber when hydrological simulation 0 0 4 gt 3 brund 1 started Minimum will be 0 0 when simulation started at 1st of January 00 00 hour Time Julian daynumber when hydrological simulation 0 0 4 lt erund ended Maximum Stepsize of time interval for dynamic hydrological data d 1 0 30 0 period Geometry of
207. ted irrigation gifts sc1 sc2 sc3 The sub model for Crop will generate files with crop growth status cr1 cr2 cr3 Formatted and unformatted binary export files for can be generated with data that cover the entire simulation period afo aun ate air These output files can be directly used as input for pesticide and nutrient models like PESTLA Berg and Boesten 1998 and ANIMO Kroes and Roelsma 1998 A description of the files afo and aun is given in annex D Three additional files will be generated automatically a file with error messages swap207 log a file with final pressure heads of all compartments Hfinal dat an empty file which is only relevant when the Graphical User Interface is applied Suc cex SC DLO TECHNICAL DOCUMENT 53 DOC 11999 185 IC 111999 6 Examples The examples in this chapter serve as exercises and intend to make you familiar with basic features of the agrohydrological model SWAP and the way input and output are arranged You will simulate a field case for water flow solute transport and crop growth in the Hupsel catchment Subsequently the following items are considered by changing the input for a reference situation and analysing the simulation results meteorological year irrigation crop type evapotranspiration of partly covered soil soil texture hysteresis of retention function scaling of soil hydraulic functions root
208. ted with no separate primary water course 3 Surface water system is simulated with a primary water course level 1 separate from the control unit the first option SWSRF 1 has been chosen the user may skip the rest of this input file For the second or third option SWSRF 2 or 3 the user has also to specify Section 2c variable SWSEC how the surface water level in the control unit is determined 1 the surface water level is simulated 2 the surface water level is obtained from input data If the third option SWSRF 3 has been chosen the user should also specify section 2b the time variation of the surface water level in the primary water course The specification is done in terms of data pairs time water level For obtaining levels at intermediate dates the program performs a linear interpolation the option is chosen to obtain surface water levels from input data SWSEC 2 the surface water level of the secondary watercourse has to be specified in the form of data pairs section 3 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 69 If the option is chosen to simulate surface water levels SWSEC 1 the user has to specify how the surface water system in the control unit functions and how it is managed section 4 Section 4 starts with some miscellaneous parameters section 4a e the initial surface water level in the control unit e the criterium for detecting oscillation of the surface water level e
209. the number of iterations to reach convergence as a criterium Making the time step range too large could lead to instability while making it too small will increase the calculation time substantially The stop criterium for the iteration procedure is defined between 1E 05 and 0 1 cm cm and basically defines convergence Choosing too large could introduce errors while choosing it too small will increase the calculation time substantially The user should check the mass balance error in the soil water output file WBA to determine if the error is acceptable The user can choose two types of implicit schemes 1 Richards equation is solved twice per time step For very simple problems under steady state or slowly changing conditions this might be appropriate 2 Richards equation is solved until convergence This is the recommended procedure for most transient unsaturated flow problems SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 153 Filename Hupsel SWA Contents SWAP 2 0 Soil water and profile data X KKK KKK KKK KKK KKK KKK KKK CK CK CK CK CK CK CK CK CK CK CK CK CK CK CK
210. the number of water management periods Section 4b for each management period the user should specify e the index of the period the date that it ends the type of watermanagent 1 fixed weir crest 2 automatic weir the water supply capacity the allowed dip of the surface water level before initiating the supply Dependent on the discharge relationship for the weir the user has to specify e either Section 4c SWQHR 1 exponential relation e or Section 4d SWQHR 2 relation given as table Section 4c for each water management period with a fixed weir crest using weir characteristics the user should specify e Size of the control unit catchment ha e A table with weir characteristics for each management period e Index for management period e Elevation H of the weir crest cm e Weir coefficient Oinpu m s e Weir coefficient D In Van Dam et al 1997 it was indicated that the head discharge relationship is described with a simple equation eq 9 10 In that equation units conform to the rest of the model code i e unit of length in cm and unit of time in d and the discharge is computed per unit of area cm cm d or cm d However in hydraulic literature e g Working Group on Hydraulic Structures 1976 head discharge relationships are given in Sl units i e m for length and s for time and the discharge is computed as a volume rate m s To facilitate the input for the user we conformed to hydraulic lit
211. ting depth The daily increase is equal to the maximum daily increase unless too few assimilates are available or the maximum rooting depth is reached 50 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Section 3 Leaf area index or soil cover fraction SWGC 1 choice between LAI 1 or soil cover fraction 2 15 SWGC 1 list leaf area index 0 12 ha ha R as function of dev stage 0 2 R If SWGC 2 list soil cover fraction 0 1 m2 m2 R as function of dev stage 0 2 R iS DVS LAI or SCF maximum 36 records GCTB 0 00 0 05 0 30 0 14 0 50 0 61 0 70 4 10 1 00 5 00 1 40 5 80 2 00 5 20 End of table ARA KKK KK KK KKK KKK KKK KK KKK KK KKK KKK KK KKK KKK KKK KK KKK KKK KK KKK KK KKK KK KKK KEK KKK KKK KKK ARA KKK KK KKK KKK KKK KKK KKK KKK KKK KKK KK KKK KKK KKK KKK KK KK KKK KKK KKK KK KKK KK KKK KK KKK KKK Section 4 crop factor or crop height SWCF 2 choice between crop factor 1 or crop height 2 Tf SWCF 1 list crop factor 0 5 1 5 R as funct
212. to the surface water We will assume that in the water repellent top layer the flow paths occupy only 40 percent of the soil volume a Initialise with reference situation described in par 6 1 execute INITIAL BAT b Change input 1 Change in the file Hupsel swa section 8 variable SWMOBI enable preferential flow by setting the variable SWMOBI to 1 Verify that the mobile fraction 0 4 in the first soil layer and 1 0 in the second soil layer and the volumetric water content in the immobile soil volume fraction 0 02 THETIM The corresponding input table in section 8 is then looking as listed under 2 2 Goto Soil profile description At page 3 section preferential flow include immobile water In the Table specify the following values for the 2 soil layers PF1 FM1 PF2 FM2 THETIM 0 0 0 4 3 0 0 4 0 02 0 0 1 0 3 0 1 0 0 02 c Execute a simulation d Verify results Compare the amount of bromide leached in 1980 for the case with uniform flow and the case with preferential flow Answer Bromide leached Uniform flow Preferential flow Unit During 1980 39 5 68 2 mg cm The results show that preferential flow due to water repellency has a large impact on the leaching of bromide 6 2 11 Drainage design Drainage design taking into account transient flow conditions is an important feature of SWAP For instance SWAP allows a design that accounts for capillary rise which decreases the required irrigation demands The program als
213. ts SWAP version 2 0 uses the soil temperatures only to adjust the solute decomposition rate Combination of the general soil 14 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 heat flux equation and the equation for conservation of energy yields the differential equation for transient soil heat flow oT d oT MEE 4 Chant 0 t heat 4 where Cheat is the soil heat capacity J cm C and Tis the soil temperature C This equation is solved either analytically or numerically In the analytical solution a uniform thermal conductivity and soil heat capacity are assumed and at the soil surface a sinusoidal temperature wave is adopted In the numerical solution the thermal conductivity and the soil heat capacity are calculated from the soil composition and the volume fractions of water and air as described by De Vries 1975 At the soil surface the daily average temperature is used as boundary condition 2 4 Solute transport SWAP simulates convection diffusion and dispersion non linear adsorption first order decomposition and root uptake of solutes This permits the simulation of ordinary pesticide and salt transport including the effect of salinity on crop growth In case of detailed pesticide or nutrient transport daily water fluxes can be generated as input for other groundwater quality models such as PESTLA Boesten and van der Linden 1991 Berg and Boesten 1998 and ANIMO Groenendijk and Kroes 1997 Kroes and
214. ultural Engineers St Joseph Mich p 163 170 smith M 1992 CROPWAT A computer program for irrigation planning and management FAO Irrigation and Drainage paper 46 Supit I A A Hooijer and C A van Diepen Eds 1994 System description of the WOFOST 6 0 simulation model DLO Winand Staring Centre Wageningen the Netherlands Van Dam J C J Huygen J G Wesseling R A Feddes P Kabat P E V van Walsum P Groenendijk C A van Diepen 1997 SWAP version 2 0 Theory Simulation of water flow solute transport and plant growth in the Soil Water Atmosphere Plant environment Technical Document 45 DLO Winand Staring Centre Report 71 Department Water Resources Agricultural University Wageningen Van Genuchien M Th 1980 A closed form equation for predicting the hydraulic conductivity of unsaturated soils Soil Sci Soc Am J 44 892 898 Wesseling J G and J G Kroes 1998 A global sensitivity analysis of the model SWAP Report 160 DLO Winand Staring Centre Wageningen The Netherlands Working Group on hydraulic Structures 1976 Discharge measurement structures Publication no 20 Institute for Land Reclamation and Improvement ILRI Wageningen The Netherlands 104 SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Annex A Output files of the Hupsel reference case 31 12 1980 Solute storage Output file Result bal 1 01 1980 until 200 00 cm Period Depth soil profile Water storage
215. valuate transpiration evaporation drainage and groundwater levels for the three simulations Answer Scaling factor 0 45 1 00 2 50 Unit Runoff 0 6 0 0 0 0 cm year Potential transpiration 29 6 29 6 29 6 cm year Actual transpiration 26 9 26 6 26 6 cm year Potential evaporation 35 0 35 0 35 0 cm year Actual evaporation 14 4 14 4 14 4 cm year Drainage 21 5 21 4 21 1 cm year Groundwaterlevels 31 March 69 8 70 0 69 9 cm 30 September 137 0 131 5 131 9 cm The results with the three scaling factors show that the water balance is not sensitive to the soil texture The water balance is mainly governed by the boundary conditions 6 2 8 Root density distribution In the reference simulation par 6 1 a triangular root density distribution was assumed In general the root density will decrease with depth especially in case of irrigation shallow groundwater tables decreasing organic matter content and increasing mechanical resistance This exercise will show the effect of changes in the root density distribution a Initialise with reference situation described in par 6 1 execute INITIAL BAT b Change input 1 Inthe file MaizeS crp section 11 variable Rdensity change the root density distribution from triangular to uniform set all values for Rdensity to 1 0 2 Goto Crop data simple model Load file MaizeS crp At page 1 section Root distribution set Rdens 1 0 for 0 0 gt Rdepth gt 1 0 In this way a uniform root
216. wth 4 11 6 Section 6 Hysteresis of soil water retention function In SWAP hysteresis only affects the water retention function The hydraulic conductivity as function of soil water content is considered uniquely defined SWAP uses the method of Scott et al 1983 to simulate hysteresis If hysteresis is simulated the user should define either initial condition wetting or initial condition drying If the soil is initially dry and is getting wet during the simulation the simulation should start from the initial condition wetting Alternatively if the initial condition is wet for instance in winter or after a rainstorm the initial condition for hysteresis should be drying A minimum head difference to change from wetting to drying cm at a soil node should be specified This parameter is introduced to prevent the program from quickly swapping from a wetting to a drying curve if small changes in the pressure head in a direction opposite to the previous direction occur hysteresis is chosen by the user the hydraulic functions should be defined with Mualem van Genuchten parameters in the soil hydraulic function file SOL If hysteresis applies similar media scaling section 7 or preferential flow due to immobile water section 8 can not be applied 4 11 7 Section 7 Similar media scaling of soil hydraulic functions This option allows the scaling of the Mualem van Genuchten parameters of the soil hydraulic function t
217. x which is specified in the file DRB Par 4 13 for basic drainage or DRE Par 4 14 for drainage extended to surface water The drainage or infiltration flux applies to local groundwater flow which is directly affected by local surface water management The drainage infiltration flux is considered to leave enter the soil profile horizontally The bottom boundary conditions which always should be specified should include the influence of groundwater flow on larger scale which is not affected by local surface water management Instead of defining the local drainage fluxes separately the user may choose to include the local drainage fluxes in the bottom boundary condition In that case the effect of changes in local surface water management on the field scale water balance cannot be simulated SWAP allows eight different bottom boundary conditions 1 Groundwater level is given 3 4 Upward flux calculated as a function of groundwater 5 Pressure head of bottom compartment is given 6 Zero flux at the bottom of the profile 7 Free drainage at the bottom of the profile 8 Lysimeter with free drainage Ad 1 Groundwater level is given Up to 366 records can be entered to describe the ground water level as a function of time Similar to other data that are given as function of time SWAP will interpolate between data pairs Note that if in file SWA section 11 an initial soil water profile in equilibrium with the groundwater level ha
218. x to compartments calculate moisture capacity from pressure head handle errors find first free even unit number calculate bottom and compartment fluxes number of days between two given dates grass growth routine for SWAP calculate hydraulic conductivity from water content calculate pressure heads at next time initialize soil profile data integrate intermediate and cumulative water fluxes initialize and calculate irrigation jump to label NAME limit variable between given boundaries return meteorological data of actual day specify crop characteristics for bare soil convert daynumber into date formatted hydrological output for ANIMO PESTLA AFO write irrigations AIR write soil temperatures ATE unformatted hydrological output for ANIMO PESTLA AUN write cumulative overview water and solute balance BAL write drainage fluxes runoff etc DRF write water balance increments INC write solute balance SBA write surface water balance SWB write soil temperatures TEP write water and solute profile data V AP write water balance WBA SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 1109 Routine AFGEN ANALIN ASSIM ASTRO BOCOBOT BOCODRB BOCODRE BOCOTOP CALCGWL CRACK CROPD CROPS DATONR DEVRIES DIVDRA DMCNODE ERRHANDL FINDUNIT FLUXES FROMTO GRASS HCONODE HEADCALC INITSOL INTEGRAL IRRIG JMPLBL LIMIT METEO NOCROP NRTODA OUTAFO OUTAIR OUTATE OUTAUN OUTBAL OUTDRF O
219. y applies 76 O SC DLO TECHNICAL DOCUMENT 53 DOC 1 1999 Filename Hupsel BBC Contents SWAP 2 0 Bottom Boundary Condition c Comment area Xi 6 kk Kk KK KK KK ck Choose one of 8 options SWOPT1 0 Switch use groundwater level Y 1 N 0 If SWOPT1 1 specify date day month and groundwater level cm neg below soil surface maximum 366 records O 01 mi GWlevel 1 95 0 31 12 110 0 End of table
220. ylength parameters The daily increase in temperature sum does not need to be linear It is conceivable that the increase is lower at higher average temperatures The relationship can be defined in a maximum of 15 data pairs Finally the development stage at harvest should be defined 4 8 3 Section 3 Initial values The initial growth parameters needed are the initial crop weight the leaf area index and the maximum relative increase of LAI 4 8 4 Section 4 Green surface area In the second assimilates limited growth stage the maximum increase in leaf area index is determined by the specific leaf area The specific leaf area of a crop can differ depending on the development stage SWAP allows introduction of a curve describing the specific leaf area in up to 15 data points as a function of the development stage To calculate total assimilation it is necessary to know the green area of the stems and storage organs since these can absorb radiation Under optimal conditions constant 35 C leaves have a certain life soan Lower temperatures limit the life soan of the leaves Next to the optimal temperature of 35 C a lower threshold temperature which is crop specific should be specified 4 8 5 Section 5 Assimilation This section contains the parameters needed to calculate the assimilation rate from the solar radiation data Detailed information about the assimilation calculations can be found in par 7 3 through 7 5 of Van Dam et al

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