VL-PRMS Documentation
Contents
1. Earth Earthfx Incorporated 3363 Yonge Street Toronto Ontario MAN 2M6 August 2013 E mmm EEN A A bg Incorporated Earth Science Information Systems VIEWLOG VL PRMS Documentation Thursday September 26 2013 The following report documents the operation of the VL PRMS Extension to the VIEWLOG Modelling System If you have any questions please call Yours truly Dirk Kassenaar M Sc P Eng President Earthfx Inc if E J Wexler M S E M Sc P Eng Vice President Earthfx Inc Tel 416 410 4260 Email support viewlog com dirk viewlog com ejw earthfx com 3363 Yonge St Toronto Ontario Canada M4N 2M6 T 416 410 4260 F 416 481 6026 www earthfx com VL PRMS Documentation VL PRMS Documentation Table of Contents 1 VL PRMS OVERVIEW idociocincincca dd 1 1 VL PRMS INTRODUCTION o enie edion orete e non iar ECEE or EAEE ONEA E AENA ak EAEEREN 1 2 USGS PRMS DOCUMENTATION 1 3 OVERVIEW OF VL PRMS CODE ENTENSIONS 1 3 1 Fully distributed Cell Based Simulation Untts 1 3 2 Additional SCS Soil Curve Rainfall Runoff Partitioning oooommcoccccnnnnn 1 3 3 Addition of Hargreaves PET Estimation Method 2 PRMS FLOW CHART 0ccceecceecceecceecceeseeeseeesenesenesensseeusenesenusenaeenseeneseneeeneeenueens 3 USGS PRMS VERSIONS AND DOCUMENTATION cccccccssescssssecssesenseseeees 3 1 PRMS VERISON 1 10872 3 1 1 1983 version Original version 1 0 Documentaton 32. ET and groundwater recharge The code is well documented in Leavesly et al 1983 For the purpose of this document the term Classic PRMS or simply PRMS refers to the open source USGS code documented in Leavesly et al 1983 while VL PRMS refers to the version customized by Earthfx Inc 1 2 USGS PRMS Documentation The original PRMS documentation is available for download from http pubs er usgs gov publication wri834238 Current information on PRMS can be found at http wwwbrr cr usgs gov projects SW_MoWS PRMS html Further information on the PRMS versions code and input file format is included later in this document 1 3 Overview of VL PRMS Code Extensions The following is a summary of the changes that differentiate VL PRMS from Classic PRMS These changes include 1 3 1 Fully distributed Cell Based Simulation Units The Classic PRMS code computes water balances for a set of Hydrologic Response Units HRUs In Classic PRMS HRUs are defined as areas e g polygons with uniform hydrologic properties and can represent a catchment or part of a catchment with a dominant soil type and land use In VL PRMS each HRU corresponds to a rectangular cell from the underlying MODFLOW model A direct correspondence between the HRUs and MODFLOW model cells is established and the terms can be used interchangeably A small cell size can be selected so that values associated with land use classes soil types and surface water
3. defines the number of rows and columns of the gridded inputs and outputs OUT Defines the output listing file This file echo s the main inputs into an ASCII format so the user can confirm operation Other MTR files ending in OUT are ASCII outputs Earthfx Inc VL PRMS Documentation 19 5 2 CG1 File Format Card Parameters The CG1 File follows the ASCII CARD GROUP file format described in the PRMS documentation Cards are documented as follows 1 All card parameters as described in Leavesley et al 1983 starting on Page 77 2 PRMS 2 1 extensions to the card parameters as described in Section 3 2 above 3 Additional VL PRMS extensions to the card parameters are describe below a Array reader inputs as described in Section 5 3 below b Other extensions as documented Section 5 4 below 5 3 VL PRMS Array Reader Data sets As noted the key benefit of VL PRMS is the fully distributed cell based operation VL PRMS reads fully distributed parameters i e cell based values from VIEWLOG binary grid files The VIEWLOG grid definition is read from a NOD file as specified in the MTR file see above VL PRMS Data cards 36 through 38 Cards as described in Leavesley 1983 are read as constants or VIEWLOG grid files For example the following few lines from a CG1 file show the array reader options Keyword Constant Grid file Name ARRAY 0 LSRCA_IBOUND_EDGE GRD ARRAY 05 0 LSRCA SlopeClass100 grd ARR
4. 1 2 Version 1 EE 3 2 PRMS VERSION 2 1 MARCH 4 19008 3 3 PRMS VERISON 3 NOV 82011 4 VL PRMS OPERATION ccccceecceecceecceesceesceuscnuscnsseesenusenesensseusenusenusenusenssenueens 4 1 INSTALLING VL PRM EE 4 2 STARTING VL PRMS c oeeeaeeaa a ae a a 4 3 LOADING AND RUNNING A VL PRMS MASTER MTR FILE seenen 5 OVERVIEW OF VL PRMS INPUT FILES ooncconncnnncninnnnco nono nr no nn no nr nn nro KEEN RKKN NEEN 5 1 MASTER MTR FILE FORMAT 5 2 CG1 FILE FORMAT CARD PARAMETERS seoesesereeeeernorerrinrrrrrrrrrrrrrrrrrerrrrreree 5 3 VL PRMS ARRAY READER DATA SETS cecceeeceeeceeeceeeceeeceeeeeeceeeceeesaeeeeeeens 5 4 VL PRMS CARD PARAMETER EXTENSIONS 0ooccoocconcconcconccnnnconanonanonaconaconaconanos Earthfx Inc VL PRMS Documentation 4 1 VL PRMS Overview 1 1 VL PRMS Introduction VL PRMS is a customized version of the USGS PRMS model adapted primarily to provide distributed cell based recharge estimates for use in the USGS MODFLOW model simulations The USGS Precipitation Runoff Modelling System PRMS model Version 2 1 is the core of VL PRMS PRMS is an open source code for calculating all components of the hydrologic cycle on a watershed or sub watershed scale PRMS is a deterministic distributed parameter model that incorporates information on the spatial distribution of precipitation temperature solar radiation soil properties vegetation and land use to yield outputs of estimated runoff infiltration
5. 12345678901234567890123456789012345678901234567890123456789012345678901234567890 Earthfx Inc VL PRMS Documentation 12 GROUP CARD COLUMNS FORMAT VARIABLE DEFIN 40 70 Ti IDOUT Store ITION predicted daily mean data 0 no storage 1 store predicted and observed daily mean streamflow values as sequential direct access data file by water year on unit 20 2 same as 1 format is standard WATSTORE daily values record 3 store obsv precip and disch computed reservoir values predicted discharge in wdm Il IUOUT Store unit values data 0 no storage 1 store predicted streamflow on unit 19 as sequential direct access data file by storm Format is standard WATSTORE unit values record 2 store in wdm file Il PROB Extended Streamflow Prediction ESP 0 do not run 1 run ESP Earthfx Inc VL PRMS Documentation 13 GROUP CARD COLUMNS FORMAT VARIABLE 12a 13a 13b 136 41 45 46 50 51 55 71 80 30 11 50 11 15 16 20 11 26 31 40 11 26 31 35 r10 0 11 815 T5 I5 A16 A16 I5 NTS NPLW NDC DAT IPOP2 DSNC I DSNP DSNP STAIDT i DSNT j i STAIDS i DSNS i DEFINITION Lapse rates D use monthly lapse rates 1 compute daily lapse rates number of temperature stations number of snowpillow stations number of snowcovered area depletion curves Total basin drainage area in acres Individual H
6. features i e wetlands and lakes can be mapped to the cells with reasonable accuracy Earthfx Inc VL PRMS Documentation 5 While Classic PRMS is limited to 50 HRU s the fully distributed VLPRMS code supports grids with over 1 million cells 1 3 2 Additional SCS Soil Curve Rainfall Runoff Partitioning Classic PRMS uses a contributing area method to estimate the Hortonian flow component of overland runoff from each HRU Earthfx added the option of using a U S Soil Conservation Service SCS curve number technique The SCS runoff curve number is based on the concept that the volume of runoff is small for small storm events but increases with the size of the rainfall event The volume of runoff depends on the soil class and land use SCS 1972 The runoff volume R is given by 2 E La Eq 1 P I 8 where P la is the effective precipitation after initial abstraction of evaporation from canopy interception and detention storage and other similar terms Initial abstraction is calculated explicitly in PRMS rather than assuming that it can be approximated as 0 2S as is often done S is the potential maximum soil moisture retention and is related to the CN value by na EE CN Based on these two relationships higher CN values yield higher runoff values CN values are assigned based on the four soil classes A B C and D with a well drained clean sand being a type A soil and a muck or clay as a type D soil For examples se
7. of Snow Pillows 4 51 55 I5 No of Snow depletion curves 4 71 80 I5 DAT Drainage area 4 81 85 I5 NRow Number of rows 4 86 90 I5 NCol Number of columns 7 46 50 I5 NOBS No of observation points to print 9 16 65 I5 IDUS 7 Baseflow 19 76 80 I5 Min PET 25a 1 80 F5 1 Snowcurve 11 points in tenths of SWE refer to GSFLOW documentation Earthfx Inc
8. progress 4 3 Loading and Running a VL PRMS Master MTR file To start a VL PRMS simulation start the program and click the Run button Clicking the Run button will direct the user to choose a Master simulation data file extension MTR Earthfx Inc VL PRMS Documentation 18 5 Overview of VL PRMS Input Files 5 1 Master MTR File Format The VL PRMS MTR file contains a list of the related input and output files that make up the simulation Each line of a MTR ASCII file contains a Component keyword for example PRE followed by a file name on the same line For example PRE stands for precipitation other components are described below A sample MTR file is as follows E LSRCA pre LSRCA pan LSRCA tem L LSRCA rad LSRCA G1 LSRCA out U daily LSRCA out Monthly LSRCA out Yearly LSRCA out Summary LSRCA out Gauge_LSRCA out LSRCA100 NOD DailyFlowStatistics out MonthlyFlowStatistics out TA AnnualFlowStatistics out OGON 1D PG GUN DANAQNNPETOCAWNHNY The following input components are defined in the master MTR file PRE Precipitation File Format year month day precip at each station PAN Pan Evaportion File Format year month day pan evap TEM Temperature File Format daily min max temp SOL Solar Radiation File Format CG1 Control File with variables as documented in the USGS PRMS documentation NOD VIEWLOG NOD file as exported from the Grid Menu in VIEWLOG
9. set numbers for sediment discharge entered in same order as flow planes and channels Required if IUOUT gt 2 PRTIN or PRTOUT must be 3 3 3 PRMS Verison 3 Nov 15 2011 PRMS Version 3 was released on Nov 15 2011 Information on this release can be found at htto wwwbrr cr usgs gov projects SW_MoWS PRMS html Since this version was released after the development of VL PRMS this documentation is not directly relevant The USGS development of PRMS Version 3 is being completed in parallel to the development of PRMS in GSFLOW The development of VL PRMS at Earthfx has now been integrated into our GSFLOW products Earthfx has implemented the code changes from VL PRMS Hargreaves PET SCS runoff partitioning into GSFLOW Earthfx Inc VL PRMS Documentation 17 4 VL PRMS Operation 4 1 Installing VL PRMS VL PRMS consistes of a single executable files and 2 dynamic link libraries As an add on to VIEWLOG it is necessary to install VIEWLOG prior to installing VL PRMS Once VIELWOG is installed the VL_PRMS file and related DLL s can be placed in and run from any directory VL PRMS requires a VIEWLOG Green USB Key with the PM option 4 2 Starting VL PRMS To start PRMS double click on the VL_PRMS EXE file name The program will appear as below Runtime Texti Figure 2 VL PRMS Main Screen During a VL PRMS simulation the three progress bars show the Year Month and Day of the current simulation
10. AY 0 0 LSRCA Slopel00 gra ARRAY 3 2808 LSRCA_TOPO GRD CONST 2 47105 const_DARU GRD The format of each line is as follows Keyword The keyword can be one of the following ARRAY read cell based parameter values from a binary VIEWLOG grid CONST read a single constant value for this parameter Constant The second value on the line is either the parameter value 0 or a grid cell multiplier For example CONST 2 47105 const DARU GRD means read a single constant value of 2 47105 ignore the array name ARRAY 0 0 LSRCA_Slope100 grd means read data from the specified grid file Earthfx Inc VL PRMS Documentation 20 ARRAY 3 2808 LSRCA_TOPO GRD means read from the grid file and multiply each grid cell value by 3 2808 to convert the values in this case from metres to feet prior to processing Note PRMS works in imperial units so this constant can be useful for converting metric values for input Grid File Name If ARRAY has been specified the last portion of the card contains the file name of the grid file 5 4 VL PRMS Card Parameter Extensions The following extensions to the Cards are used to enable the VL PRMS options Card Columns Format Variable Description 2 20 11 IPET IPET 3 Hargreaves formulation 2 25 11 ISSR1 ISSR1 2 SCS CN Number approach 4 16 20 I5 NDS Changed to NOBS No of observation points 4 41 45 I5 No of Temperature Stations 4 46 50 I5 No
11. RMS to compute PET using the simpler Hargreaves model see Hargreaves and Allen 2003 or Wu 1997 which requires only two climatic parameters temperature and incident radiation PET in mm day is given by PET 0 0135 T 17 78 Rs 238 8 595 5 0 55T where T is the mean temperature in C and Rgsis the incident solar radiation in megajoules per square meter per day MJ m day The incident solar radiation is adjusted for each HRU based on slope and aspect vegetation type winter summer cover density and winter transmission factor e percentage of short wave radiation through the winter vegetation canopy Actual ET depends on the soil type and amount of water in interception storage and in the recharge zone upper part of the active soil zone If the amount of water in interception storage is insufficient to meet the PET demand the deficit is extracted from the recharge zone at a rate based on soil type and the ratio of the current volume of water stored in the recharge zone to the maximum storage capacity If the PET demand is still not met then moisture is extracted from the lower part of the active soil zone but at a rate based on soil type and the ratio of the current volume of water stored in the lower soil zone to the maximum in storage capacity Soil zone depth was defined by the average rooting depth of the predominant vegetation and adjusted in areas of shallow water table Initial storage in the upper soil zone was determined b
12. RU values print switch 0 no print 1 annual summary 2 1 plus monthly summary 3 2 daily summary 4 write HRUs or combinations of HRUs sub basins to wdm file record types SBSNS and DSNSB required WDM data set number for data types 1 thru 8 Card follows card 12 WDM data set number for data type 9 for each rain gage data set WDM data set number for data type 10 for each rain gage data set There will be a set of cards 13 and 13a for each rain gage data set Station ID for temperature station i ANNIE WDM data set number for maximun j 1 and minimum j 2 air temperature data for station i One record 13b for each temperature sta Station ID for snowpillow station i ANNIE WDM data set number for snowpillow data for station i Earthfx Inc VL PRMS Documentation 14 GROUP CARD COLUMNS FORMAT VARIABLE L 17a 18 18a 18c 36 40 K r 41 45 F5 2 11 15 I5 6 75 12F5 0 1 60 5F10 0 1 80 14F5 2 1 80 14F5 2 RTB RTC ITSOL TSOLX ARSA ARSM CSEL i PCR 3 PCS j DEFINITION One record 13b for each snowpillow station Y intercept of temperature range TMAX HRU TSOLX MO estimated solar radiation adjusted factor PA relation Slope of temperature range estimated solar radiation adjustment factor PA relation HRU used to computed daily temperature range TMAX HRU TSOLX MO used in computation of solar radiation adjustment fac
13. ased on the thickness of the recharge and soil zones multiplied by the available water The water available for ET is equal to the difference between field capacity Excess water defined as the soil moisture above field capacity is allowed to percolate to the subsurface reservoir Percolation to groundwater is assumed to have a maximum daily limit and excess infiltration is diverted to the subsurface reservoir A daily limit was assumed based on the hydraulic conductivity of the soil at field capacity assuming a unit gradient Water in the subsurface reservoir can discharge to streams as interflow or infiltrate back to the groundwater reservoir over time For this study it was assumed that interflow was a small component of the overall water budget and assigned properties that allowed most of the water in the subsurface reservoir to drain back to the groundwater reservoir The groundwater reservoir discharges to baseflow at a rate dependent on a discharge coefficient and the volume of water stored in the groundwater reservoir In these simulations the exponential decay coefficient was approximated by visually comparing the simulated recession with that observed in the streamflow hydrographs References Hamon W R 1961 Estimating potential evapotranspiration Journal of the Hydraulics Division Proceedings of American Society Civil Engineers 87 107 120 Hargreaves G A and Allen R G 2003 History and evaluation of Hargreaves evapotran sp
14. e Suphunvorranop 1985 for typical dry season drained conditions CN values are increased when the moisture content increases based on antecedent rainfall and the position of the water table so that runoff is higher under poorly drained conditions Land use types that generate more runoff have higher CN values such that a good quality forest more than 50 cover on type B soil has a CN value of 55 row crops on the same soil have a value of 78 while commercial areas typically have a CN value of around 92 The input files changes necessary to utilize this option are described in the following sections References Suphunvorranop 1985 Technical Publication No 85 5 A guide to SCS runoff procedures St Johns River Water Management District Project Number 15 20 200 03 July 1985 Soil Conservation Service 1972 National Engineering Handbook Section 4 Hydrology U S Department of Agriculture Soil Conservation Service Washington D C U S Department of Agriculture Soil Conservation Service 1985 National engineering handbook Section 4 Hydrology USDA SCS Washington D C Earthfx Inc VL PRMS Documentation 6 1 3 3 Addition of Hargreaves PET Estimation Method Water entering the soil in pervious areas is subject to evapotranspiration The PRMS code has three methods for calculating potential ET daily pan evaporation the Hamon 1961 method and the Jensen and Haise 1963 method A fourth option was added to VL P
15. estigations Report 95 4085 Earthfx Inc VL PRMS Documentation 11 MASTER CONTROL FILE RCRD COLUMNS FORMAT VARIABLE DESCRIPTION 1 FILE CONTROL RECORD Min of 3 Max of 7 File names may be entered in any order 1 3 A3 CODES Identifier for file type see below for required values 11 74 A64 NAME Name of file May be any name that is valid on the computer system being used May include the complete path name if necessary The length of the file name may be restricted on some machines CODES Required Description ERA opt Comment record WDM yes WDM file containing observed data Simulated data may be output to this file CG1 yes Card group 1 parameter and variable initialization CG2 opt Card group 2 storm period selection CG3 opt Card group 3 infiltration upland erosion parameters CG4 OPT Card group 4 flow amp sediment routing specifications CG5 opt Card group 5 precipitation form adjustment CG6 opt Card group 6 snowpack adjustment CG7 opt Card groups 7 and 8 optimizations and sensitivity OUT yes Model output print file QDY opt output predicted daily flow unit 20 QUN opt output predicted unit flow unit 21 PLT opt output daily plots unit42 HRU opt print hru unit 43 Example 1 2 3 4 5 6 7 8 12345678901234567890123456789012345678901234567890123456789012345678901234567890 WDM cane wdm CG1 test03 g1 CG2 test03 g2 CG3 test03 g3 CG4 test03 g4 OUT test03 out T 2 3 4 5 6 7 8
16. ir storage capacity is exceeded the surplus is assumed to run off Water is removed from canopy and detention storage by evaporation Total detention storage was assumed to be small due to the limited amount of impervious surface area under Current Conditions For pervious areas the model first computes canopy interception The amount intercepted depends on the vegetation type and winter summer vegetation cover density Water is removed from the canopy by evaporation Actual ET depends on the soil type and amount of water in canopy interception storage and in the recharge zone upper part of the soil zone reservoir If the amount of water in canopy interception storage is insufficient to meet the potential ET demand the deficit is extracted from the lower zone but at a reduced rate based on soil type and the ratio of the storage capacity of the lower soil zone to the current volume in storage Soil zone depth is typically defined by the average rooting depth of the predominant vegetation References Markstrom S L Niswonger R G Regan R S Prudic D E and Barlow P M 2008 GSFLOW Coupled ground water and surface water flow model based on the integration of the Precipitation Runoff Modeling System PRMS and the Modular Ground Water Flow Model MODFLOW 2005 U S Geological Survey Techniques and Methods 6 D1 240 p Earthfx Inc VL PRMS Documentation Precipitation I i Evaporation Sublimation i Air temperat
17. iration equation J ASCE Irrigation and Drainage Eng Volume 129 Issue 1 pp 53 63 Jensen M E and Haise H R 1963 Estimating evapotranspiration from solar radiation Journal of Irrigation and Drainage Div ASCE 89 IR 15 41 Earthfx Inc VL PRMS Documentation 7 Wu I P 1997 A Simple evapotranspiration model for Hawaii The Hargreaves model College of Tropical Agriculture and Human Resources University of Hawaii at Manoa Cooperative Extension Service CTAHR Fact Sheet Engineer s Notebook no 106 May 1997 2 PRMS Flow Chart A schematic flow chart modified from Markstrom and others 2008 describing the operation of the PRMS model is shown below Each of the boxes in the diagram represents a storage reservoir in a single cell The arrows represent the transfer of water from one reservoir to another or to an ultimate point of discharge e g the atmosphere or a stream or lake Processes related to snowpack accumulation and snowmelt were bypassed in simulations of the study area The model tracks the volume of water in each storage reservoir as well as the flows between reservoirs each day Each HRU can contain pervious and impervious surfaces and the water balance for each area is computed separately For impervious areas the model first computes capture of precipitation by canopy interception if any and detention storage e g water captured on flat roofs or puddles in parking lots If the impervious zone reservo
18. on 2 1 This version included the following documentation changes The version 2 1 code changes are implemented in VL PRMS and therefore the following documentation and notes are applicable and should be considered supplemental to the Verison 1 documentation From USGS This version of PRMS is documented below A few minor changes have been made to input card groups 1 and 4 The biggest program change is the way the time series data is accessed Time series data is read from a WDM file WDM files are created using IOWDM PRMS outputs time series data to WDM files These files are documented in the references listed below REFERENCES Johanson R C Imhoff J C and Davis H H Jr 1981 User s Manual for Hydrological Simulation Program FORTRAN HSPF Release 7 0 Environmental Research Laboratory Athens Ga Leavesley G H Lichty R W Troutman B M and Saindon L G 1983 Precipitation Runoff Modeling System User s Manual U S Geological Survey Water Resources Investigations 83 4238 Lumb A M Kittle J L and Flynn K M 1989 Users Manual for ANNIE a Computer Program for Interactive Hydrologic Analyses and Data Management U S Geological Survey Water Resources Investigations Report 89 4080 Flynn K M Hummel P R Lumb A M and Kittle J L User s Manual for ANNIE Version 2 a Computer Program for Interactive Hydrologic Data Management U S Geological Survey Water Resources Inv
19. record identifier data set numbers for daily output required when IDOUT 3 data written to wdm dsn for non zero entries 1 simulated flow 2 precipitation 3 potential evaporation 4 actual evapotranspiration 5 available soil moisture 6 ground water contribution 7 subsurface contribution 8 surface contribution record identifier number of sub basins to be written to the wdm file max of 50 record identifier output data set number for this sub basin number of HRUs in this sub basin max of 50 1215 KHRUSB k n index numbers of the HRUs contained in DSNSB this sub basin first 12 record identifier 1215 KHRUSB k n index numbers of HRU s contained in this sub basin 12the and greater and 45 if needed for each sub basin Print switch 0 no Earthfx Inc VL PRMS Documentation 16 37 11 PRTOUT 4 35 11 PRTIN 37 El PRTOUT 4 5 11 50 1015 DSNOQ 4 6 11 50 1015 DSNS WN i B O H 5 e WNER print rainfall excess plot rainfall excess save in wdm file outflow switch no print outflow plot outflow save outflow in wdm file inflow switch no print inflow to segment plot inflow to segment save inflow in wdm file outflow switch no print outflow from segment plot outflow from segment save outflow in wdf file data set numbers for segment discharge entered in same order as flow planes and channels Required if IUOUT gt 2 PRTIN or PRTOUT must be 3 data
20. tor PA Maximum daily air temperature below which solar radiation adjustment factor PA equals RTB for months Jan Dec Minumum snowfall in water equivalent needed to reset snow albedo during snowpack accumulation stage Minimum snowfall in water equivalent needed to reset snow albedo during the snowpack melt stage elevation of climate stations in feet i 1 nts override value for DRCOR for period MPCS to MPCN j 1 nru override value for DSCOR for period MPCS to MPCN j 1 NRU Earthfx Inc VL PRMS Documentation 15 GROUP CARD COLUMNS FORMAT VARIABLE 41 42 43 44 45 one record 44 41 45 46 50 51 55 56 60 61 65 11 75 1 5 11 50 11 15 16 20 21 80 21 80 I5 KTS 15 KSP LS KDC 15 AIMX F5 2 PKFAC 11F5 2 SCA 3 k DSNDV 815 DSNDV SBSNS 15 NSB DSNSB I5 DSNSB n LS NHRUSB n DEFINITION index of temperature station to use index of snowpillow station to use index of snowcovered area depletion curve to use maximum threshold snowpack water equivalent AI below which the snowcovered area depletion curve is applied snowpack water equivalent adjustment factor snowpillow KSP Areal extent of snow cover as decimal fraction for each 0 1 increment of the ration of areal water equivalent to the threshold water equivalent AI j 1 NDC k 1 11 for 0 0 to 1 0 in increments of 0 1 one record 41 for each areal depletion curve
21. ure i Evaporation and Transpiration Evaporation Impervious Zone Reservoir Interflow or subsurface flow to stream or lake Surface runoff to stream or lake Transpiration Groundwater seepage j d Subsurface recharge 4 Ground water recharge Ground water discharge to stream or lake Ground water sink Figure 1 PRMS Flow Chart Earthfx Inc VL PRMS Documentation 9 3 USGS PRMS Versions and Documentation 3 1 PRMS Verison 1 1983 3 1 1 1983 version Original version 1 0 Documentation VL PRMS is based on the original PRMS Version 1 inputs as documented in Leavesley G H Lichty R W Troutman B M and Saindon L G 1983 Precipitation Runoff Modeling System User s Manual U S Geological Survey Water Resources Investigations Report 83 4238 207 p This document can be downloaded from the USGS Web site at http pubs er usgs gov publication wri834238 VL PRMS Note VL PRMS follows the primary documentation of the model input file format included on pages 77 92 3 1 2 Version 1 Updates 1984 version A WDM file replaces the ISAM file for the time series data management 1991 version Added option to output computed time series to the Watershed Data Management WDM file VL PRMS note WDM files are not used by VL PRMS so these changes are not applicable Earthfx Inc VL PRMS Documentation 3 2 PRMS Version 2 1 March 4 1996 On March 4 1996 the USGS released PRMS Versi
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