BASDEV user manual
Contents
1. Calculation Mode 2 Dimensions Calculation Mode 2 is the reverse of Calculation Mode 1 the flow rate is now known and you want to know the approximate basin dimensions that are needed to achieve a reasonable performance The program will also give you the required cutoff time together with the primary performance indicators and infiltrated depths BASDEV uses a standard length width ratio of 1 ie square basins for the calculation of the basin dimensions The resulting application efficiency is similar to that in Mode 1 Here again the calculated values for basin dimensions and cutoff time are only a first shot In Mode 3 you can change the size and shape of the basin to try to increase the application efficiency eg by decreasing the basin dimensions Calculation Mode 3 Cutoff time Calculation Mode 3 is one of the two main modes of BASDEV It will be the most frequently used and is the starting mode for the experienced user Here both the flow rate and basin dimensions are input The required cutoff time is the resulting decision variable while also the primary performance indicators and depth and time parameters are given The calculated cutoff time is such that the minimum infiltrated depth is equal to the required depth This mode is suitable for a quick try out of the various options for design and operation Calculation Mode 4 Minimum depth In Calculation Mode 4 the other main mode the cutoff time is specified as inpu2. families 1 Flow rate View Print Length Time rated families 2 Dimensions Depth Kostiakov equation 3 Cutoff time Time 4 Min Depth 51 Depth millimetres centimetres or inches These are used for the various supplied and infiltrated depths Time minutes or hours These are used not only for advance cutoff depletion and recession time but also for the infiltration equa tions The selected units are maintained throughout the program and are also saved with the file When the program is started default units are litres per second for flow rate metres for basin dimensions millimetres for infiltrated depths and minutes for time 5 1 3 Sub menu infiltration In the sub menu Infiltration you can select one of three infiltration input modes Table 5 1 All the modes are based on the infiltration characteristics of a soil as described by the Kostiakov equation Equation 3 1 Di kTA where D is the cumulative infiltration after an infiltration opportunity time T Ais the infiltration exponent and k is the infiltration constant In BASDEV you can enter the soil infiltration characteristics A and k indi rectly by using the Modified SCS Intake Families and the Time Rated Families or directly by giving values to A and k For more background infor mation on this subject the reader is referred to Chapter 3 Section 1 1 The default infiltration input mode is the Modified SCS family 5 1 4 Sub menu calculation
3. how to change these values in order to get a result The above ranges are ignored for output results so no warning will be given if an out of range value obtained is subsequently used as input in another mode 5 3 Output window Once all input has been entered press F2 for the calculation and output The screen again shows the two input windows but a third window has now been added showing the results Figure 5 2 These are depicted in various groups separated by a blank line The first group contains the desired decision variables according to the selected calculation mode In Mode 1 they are the flow rate and the cutoff time in Mode 2 the basin dimensions and the cutoff time in Mode 3 it is the cutoff time and in Mode 4 it is the minimum infiltrated depth The second group contains the primary performance indicators as discussed in Chapter 3 Section 3 In Modes 1 2 and 3 this is the application efficiency with the maximum and average infiltrated depths in Mode 4 the storage efficiency and the distribution uniformity are added Finally there is a group with various time parameters The output results for the various modes are listed in Table 5 4 Note the distribution uniformity DU is not given in Modes 1 2 and 3 because it equals the application efficiency for basin irrigation as long as the required depth is achieved which 57 FIELD PARAMETERS INPUT DECISION VARTABLES ER Fo Gaon FA Save Fig
4. scaled to facili tate a solution to the equations It is impossible to do this in such a way so that all combinations of all parameters can be solved As a result a calcula tion problem may occur with some combinations of extreme values of param eters although the input ranges given in Section 5 2 3 have been fixed so as to avoid too many problems Note a problem such as this is always related to a virtual poor irrigation performance an unacceptably low application effi ciency or excessive under irrigation This will not happen if you use a combi nation of input parameters that will result in the performance you will nor mally try to achieve Physical problems The combination of input values could be such that it is physically impossible to get a result This can happen for instance with small flows on large basins or with very light soils and large basins In these cases Modes 1 2 and 3 will flash you a message on the screen because the required depth cannot be realised or in Mode 4 when the flow will not reach the end of the basin at all This is not a calculation problem but a signal that it is physically impossible to get a result with the given set of input values Cutoff time problem The calculation algorithm and the solution procedures of BASDEV cannot handle a cutoff time that is substantially shorter than the advance time For instance a high flow rate in a short basin will give a short advance time but because of th
5. 5 BASDEV user manual BASDEV is a modular menu driven computer program developed to solve problems in the design operation and evaluation of level basin irrigation sys tems You start the module by selecting it in the SURDEV package The installation procedure of this package was discussed in Chapter 4 Section 1 5 1 Menu structure There are five main menu items four of which have sub menus that you can select by moving the highlight with the arrow keys and pressing Enter or by typing the red bold character Table 5 1 shows the structure of the main menu and its first layer of sub menus 5 1 1 Sub menu files In the sub menu Files there are two options Load and View Print With Load you can select an existing file and continue with the calculations With View Print you can select an existing file the contents of which will be dis played on the screen Pressing F5 gives you the option to print this file or to save it as a text file or spreadsheet file For more information on these topics see Chapter 4 Section 4 3 5 1 2 Sub menu units The sub menu Units gives you a choice of units for flow rate length depth and time which include Flow rate litres per second cubic metres per minute cubic feet per sec ond or US gallons per minute Length metres or feet These are used for basin length and width Table 5 1 Basdev menu structure Files Units Infiltration Calculation Quit Load Flow rate Modified SCS
6. EV will internally use the corresponding values for Kostiakov s Aand k You can check this by following the same procedure as outlined above for the modified intake families If the Kostiakov equation is selected the exponent A and the coefficient k must be specified Under the Help key F1 you will find a table with A and k values corresponding approximately to various soil types Conversion of A and k values for other than the default units can be done as follows go back to the Units menu change time and depth units and return to the Field Parameters window where the new values with their mod ified units will appear Flow resistance The value of Manning s roughness coefficient n can be specified in the Field Parameters window Accepted values range between 0 01 and 0 50 For prac tical purposes however values given in Table 3 5 are recommended This table is also available under the Help key F1 when the cursor is on the n value Required depth The required depth to be infiltrated at the end of the basin is given as the last input in the Field Parameters window This target 1s determined outside BASDEV as indicated in Chapter 3 Section 1 3 The accepted range is between 40 and 500 mm 55 5 2 2 Decision variables The decision variables in surface irrigation are normally the field dimensions length and width flow rate and cutoff time Which of these parameters appear under the heading Input Decision Var
7. The sub menu Calculation is the only place in BASDEV where the input data can be entered but before doing this you need to select one of four different calculation modes Table 5 1 What the first three modes have in common is that the calculated minimum infiltrated depth at the downstream end of the basin always equals the required depth In other words no under irrigation will occur and there will always be over irrigation in the upstream part When to use the various modes is summarised below Calculation Mode 1 Flow rate Calculation Mode 1 is primarily for design purposes when the dimensions of the basin are known and you want to know the approximate flow rate that is needed to achieve a reasonable performance The program will also give you 52 the required cutoff time and the primary performance indicators as well as various depth and time parameters We emphasise that Mode 1 does not give a best solution It only serves as a first shot at a reasonable application efficiency Depending on the type of soil and the required depth the resulting efficiency in this mode varies between 70 and 95 per cent This efficiency can be increased in Calculation Mode 3 eg by increasing the flow rate If an inexperienced user were to start straightaway with Mode 3 he may inappropriately select values of input vari ables that give a poor performance or even error messages Starting with Mode 1 avoids too many trials or error messages
8. e high flow rate the cutoff time being the required volume divid ed by the flow rate may be even less The same problem could occur if the specified cutoff time in Mode 4 is too short No single remedy can be given to circumvent this problem and suggestions on the screen therefore vary with the calculation mode As long as the flow is cut off when advance has passed 90 of the basin length the program will give a result With cutoff when advance is between 90 and 100 of the field length computation results will be somewhat inac curate but they will be acceptable for practical purposes Many runs with BASDEV have shown that the occurrence of this type of problem gives inadequate results anyhow You can verify this by generating such an error message in Mode 3 or 4 and then gradually changing one of the input values as recommended by the message This will lead to a rather poor first result too much under irrigation in Mode 4 or a very low application effi ciency in Mode 3 60 5 5 Assumptions and limitations The BASDEV program is based on a model that is assumed to represent the process of basin irrigation This model described in detail in Appendix A involves assumptions on the validity and accuracy of the algorithm used and also on the procedures to solve the equations The use of BASDEV is thus lim ited to conditions where these assumptions are valid In addition the model itself is a schematisation that includes a n
9. eby the total inflow is divided by the basin width This allows a two dimensional calculation of the surface flow on a one metre wide strip surface flow in length direction and infiltration in vertical direction Slight variations eg when inflow is distributed over the width by an ade quate number of siphons will not produce a severe limitation on longer fields because flow from the siphons will rapidly spread out to form one straight front If water is supplied from one inlet point however a head ditch can be made to make basin inflow more uniform For situations with a point inlet Clemmens et al 1995 state that for length width ratios of gt 2 the location of the inlet has no effect on advance For basins that are almost square they recommend using the diagonal distance as the field length and using a calculation width that is the actual basin area divided by the diagonal distance Inflow is constant during the supply period A deliberate inflow cutback is 61 not needed with basin irrigation because there is no surface runoff In practice fluctuations in flow rate may occur Minor fluctuations around the intended value will not be a problem because their effect is levelled out during advance especially if cutoff occurs later than advance time Reddy and Clyma 1982 showed that this also applies to larger variations The influence of systematically lower or higher inflows can be assessed with BASDEV itself Infiltratio
10. ect when the flow rate is increased from 80 to 90 I s 4 The results of this run Table 5 6 Run 3 show that there is now a slight over irrigation the minimum infiltrated depth is 104 mm and the applica tion efficiency is reduced to 82 So there is scope for reducing the flow rate 65 Table 5 6 Basdev program for level basin irrigation Filename EXAMPLE2 Run no 1 2 3 4 Calculation Mode 1 2 3 4 Input parameters Units Flow rate s l 80 90 85 Basin length m 100 100 100 100 Basin width m 80 80 80 80 Cutoff time min 180 180 180 Required depth mm 100 100 100 100 Flow resistance 0 15 0 15 0 15 0 15 SCS Time rated T min Inf par A 0 68 0 68 0 68 0 68 Inf par k mm min A 2 27 221 2 27 2 27 Output parameters Flow rate l s 80 Basin length m Basin width m Cutoff time min 201 Applic efficiency o 83 91 82 87 Storage efficiency 98 100 100 Distribution unif 80 86 83 Min inf depth mm 86 104 95 Max inf depth mm 133 121 132 126 Average depth mm 121 108 122 115 Over irr depth mm 13 22 16 Under irr depth mm 7T 0 2 Over irr length m 75 100 91 Under irr length m 25 0 9 Advance time min 135 135 117 125 Recession time min 397 345 394 369 somewhat Run Mode 4 again to see the effect when the flow rate is decreased from 90 to 85 Vs 5 This run Table 5 6 Run 4 shows that the EE IR i
11. error mes sage with a list of acceptable numbers is shown Instead of typing a number you can also use the help screen by pressing F1 while keeping the cursor on the family number A screen with family numbers will then pop up from which you can make your selection The same screen also shows the corresponding approximate soil types as shown in Figure 5 1 When a family number has been selected the corresponding values for Kostiakov s A and k are used internally by the program see Table 3 2 You can check this by selecting a family number going back to the sub module Infiltration type selecting Kostiakov mode and returning to the input window again which then shows the corresponding A and k values If you select Time Rated Families you must specify the time required to infil trate 100 mm Tjo9 in the Field Parameters window Although originally seven time rated intake families were presented see Table 3 4 the program Table 5 2 Input variables for the Basdev calculation modes Input variables Mode 1 Mode 2 Mode 3 Mode 4 Field Parameters Infiltration O o o o Flow resistance n o o o o Required depth Dreq o o o o Input Decision Variables Length L o o o Width W o o o Flow rate Q o o o Cutoff time Teo o 54 FIELD PARAMETERS INPUT DECISION VARIABLES S C S Intake families Figure 5 1 Selecting an intake family accepts any value ranging between 10 and 2000 minutes If you assign a value for Tyo9 BASD
12. es 6 In the input window you can specify field parameters and decision vari ables after which you can run the program with F2 7 You can view the results of each run in tabular form in the output window or in graphical form with F3 The results of one simulation run output and input in one file can be saved in a separate file or can be appended to earlier runs in an existing file with F4 8 Select Files and View Print from the main menu to see what has been done and or to print a file directly or convert it to a print file for a word proces sor program or convert it to a file that can be imported into a spreadsheet program where you can carry out further analyses and make your own graphs 5 7 Sample problems In most cases the user will not be satisfied with a solution obtained after one run and he will usually do a number of runs to get an acceptable solution Two simple examples are given to illustrate this procedure For more elabo rate problems see Chapter 8 Section 1 5 7 1 Determine basin dimensions A design is to be made for a situation where the available flow rate is fixed at 30 l s The soil type is sandy loam and can be classified with the Modified SCS family 1 5 Table 3 2 The net irrigation requirement is 80 mm The crops are grown in rows in the direction of flow so the value of the flow resistance can be taken as 0 20 Table 3 6 Determine the basin dimensions in such a way that the application eff
13. h should also include topographic agricultural economic and social aspects In addition one should take into account the relationships between field irriga tion the water distribution in the tertiary unit and the supply regimes in the main system Therefore an overriding assumption of BASDEV is that the user is fully aware of its limitations and must give due consideration to all these other aspects as well 5 6 Program usage The following eight steps are important in the usage of the BASDEV program 1 Start the SURDEV package Select BASDEV from the main menu of SURDEV i i 2 If you want to use an existing file retrieve it with the Load command under the Files menu If you want to make a completely new file go 62 straight to the Calculation menu bypassing the Files menu and you will get the default data 3 If you normally work with the default unit settings you can skip the Units menu Select Units only if you want to work with other units 4 Specify which type of infiltration characteristics you will be inputting in the Infiltration menu The program default is the Modified SCS families infiltration type 5 Go to the Calculation menu and select a mode to work in Most of the work will be done in Modes 3 and or 4 Less experienced users can start in Mode 1 or 2 to get a first estimate of flow rate or field dimensions respectively Mode 4 can be used to evaluate an existing situation or to do sensitivity analys
14. iables depends on the selected calculation mode see Table 5 2 Basin dimensions You can prescribe values for the basin length and width in Calculation Modes 1 3 and 4 In Mode 3 increasing the length will lower the performance because the advance time with the given flow rate will be longer Applying a larger flow will then enable a greater length In Mode 4 when using the pro gram for evaluation purposes you either prescribe the basin dimensions of an existing situation or you keep them as determined in Mode 3 Flow rate Flow rate values can be given in Calculation Modes 2 3 and 4 Decreasing the flow rate too much would result in the flow not reaching the end of the field Contrarily there is also a practical upper limit above which the performance will hardly improve see Chapter 8 Section 1 1 In Mode 4 you either keep the flow rate as determined in Mode 3 or when using BASDEV for evaluating an existing situation take the value from the field Cutoff time Values for the cutoff time can only be given in Calculation Mode 4 there are however practical limitations to changing its value When you go to Mode 4 after having run Mode 3 the displayed cutoff time corresponds to a situation where the minimum infiltrated depth at the downstream end of the basin matches the required depth Increasing the cutoff time will result in over irri gation and a lower application efficiency On the other hand if you decrease the cutoff time
15. ically adds the extension TXT to the file name EXAMPLE1 If you now exit BASDEV you can load the results in a word processing program by retrieving the file EXAMPLE1 TXT This is how you make Table 5 5 5 7 2 Determine flow rate A design is to be made for an existing basin of 100 by 80 m From infiltrome ter tests the parameters of the Kostiakov equation were determined as A 0 68 and k 2 27 mm min The net irrigation requirement is 100 mm The flow resistance broadcast small grains can be taken as 0 15 Determine the flow rate in such a way that the application efficiency is at least 80 per cent and the cutoff time is not more than 3 hours 1 Go to the Infiltration menu and select the Kostiakov equation Go to the Calculation menu and select Mode 1 Flow rate Enter the above values in the two input windows and make a run 2 The results of this run Table 5 6 Run 1 show that this basin can be irri gated with an application efficiency of 83 per cent given a flow rate of 80 l s A cutoff time of 201 minutes will then be required implying that the cutoff time needs to be reduced Run BASDEV in Mode 4 to see the effect when the cutoff time is reduced from 201 to 180 minutes 3 The results of this run Table 5 6 Run 2 show that although the applica tion efficiency increased to 91 per cent there is under irrigation the min imum infiltrated depth is 86 mm instead of the required 100 mm Run BASDEV again in Mode 4 to see the eff
16. iciency is at least 80 per cent and the cutoff time has a practical value The maximum possible basin length is 30 m 1 We want to make a new file and therefore need not use the Files sub 63 menu Observe that the default units and infiltration modes are to be used in this problem so you can go directly to the Calculation menu and select Mode 2 Dimensions Enter the above values in the two input windows and make a run F2 2 The results of this run Table 5 5 Run 1 show that with an available flow rate of 30 l s a square field of 28 by 28 m can be irrigated with an applica tion efficiency of 88 per cent This is sufficiently high but the basin length is less than the maximum Go to Mode 3 to see the effect when the basin dimensions are increased to 30 by 30 m 3 The results of this run Table 5 5 Run 2 show that the slightly larger basin causes a reduction in the application efficiency from 88 to 86 per cent which is still acceptable The cutoff time however has an impracti cal value Therefore we now go to Mode 4 to see the effect when the cutoff time is reduced from 47 to 45 minutes Table 5 5 Basdev program for level basin irrigation Filename EXAMPLE1 Run no 1 2 3 Calculation Mode 2 3 4 Input parameters Units Flow rate l s 30 30 30 Basin length m 30 30 Basin width m 30 30 Cutoff time min 45 Required depth mm 80 80 80 Flow resistance 0 20 0 20 0 20 SCS 1 5 1 5 1 5 Time rated T
17. length of the field Where applicable under and over irrigation are indicated The graph can be saved if you press F8 or F9 depending on whether you want to print it in colour or in black and white Figure 5 3 shows a graph that was made by running BASDEV in Mode 4 with default values except for the cutoff time which was taken as 50 minutes You can save the tabulated simulation results together with the input data by pressing F4 In a small window the path folder file name can be con firmed or changed as described in Chapter 4 Section 3 3 You can overwrite the previous file or append the current results to it Further processing of the saved results file must be done under the Files menu using View Print see Chapter 4 Section 4 5 4 Error messages When you start with Mode 1 or 2 to get proper initial estimates BASDEV will usually give an output as a result of the calculations Yet particularly when working in Modes 3 and 4 BASDEV may flash you error messages on the screen Such an error message will usually start with Change one or more input parameters and be followed by suggestions on which parameter to decrease or increase 59 The suggestion will depend on the mode and on the input value Possible prob lems can be grouped into three categories ie computational problems phys ical problems and cutoff time problems Computational problems In the calculation algorithm of BASDEV the parameters are
18. min Inf par A Inf par K mm min A _ Output parameters Flow rate l s Basin length m 28 Basin width m 28 Cutoff time min 41 47 Applic Efficiency Jo 88 86 89 Storage efficiency 100 Distribution unif 85 Min inf Depth mm l 77 Max inf Depth mm 98 101 98 Average depth mm 91 93 90 Over irr Depth mm li Under irr Depth mm 2 Over irr Length m lt 27 Under irr Length m 3 Advance time min 25 30 30 Recession time min 102 106 102 64 4 The results of this run Table 5 5 Run 3 show that the reduction in cutoff time results in a slight under irrigation the minimum infiltrated depth is now 77 mm instead of 80 mm but the storage efficiency is still 100 per cent see also the graph F4 Furthermore the advance time is 30 minutes so cutoff can be done 15 minutes after advance The application efficiency has increased to 89 per cent and the distribution uniformity is 85 per cent These results are acceptable Table 5 5 can be made with BASDEV The procedure is as follows Save Run 1 with F4 and specify a file name EXAMPLE1 BASDEV automatically adds the extension BCR to this file name Save Runs 2 and 3 with F4 under the same file name using the Append option Go back to the main menu go to Files menu select View See the results and select F5 Print Save and then use the option Text File BASDEV now automat
19. n and flow resistance are uniform over the basin area Substantial variations in infiltration will certainly affect the performance but to what extent this occurs depends on the values of the other parame ters Variations in flow resistance usually have less influence Resistance that is generally higher than assumed will result in the advance time being later consequently performance will be poorer Calculations of design and performance sensitivities can indicate the accuracy required in these inputs The basin surface is level in all directions A slight gradient lengthways is acceptable eg up to half the maximum flow depth the calculations there of need not be adjusted because the advance will be faster and the practical result would be a slightly better performance than calculated Slopes across the field however should always be avoided Undulations high and low spots seriously affect the performance because the surface flow first has to fill the low spots before it can overcome the higher spots This can be avoid ed by proper levelling Deviations of about 15 mm as achieved with laser controlled levelling have little effect but deviations of more than 40 mm are not acceptable Dedrick et al 1982 Finally we must emphasise that BASDEV only deals with the technical hydraulic aspects of basin irrigation In a proper design or operation the pro gram result only constitutes one element of the total considerations whic
20. of Mode 3 in Mode 4 you will introduce under irrigation yield ing a higher application efficiency but a storage efficiency becoming lower than 1 The cutoff time should not be much shorter than the advance time calcu lated for the same input combination This would give an unacceptably poor result or even an error message because insufficient water will reach the end of the field or no water at all 5 2 3 Input ranges As shown in Table 5 3 ranges have been fixed for all input variables and are in metric units If other units are chosen in the menu the indicated ranges are converted in the program 56 Table 5 3 Accepted ranges of input parameters Input parameters Accepted values Field Parameters SCS family 0 2 4 0 Time rated T 10 2000 min Infiltration coefficient k 0 8 45 0 mm min Infiltration exponent A 0 2 1 0 Flow resistance n 0 01 1 00 Required depth Dreq 40 500 mm Input Decision Variables Basin length L 5 800 m Basin width W 5 500 m Flow rate Q 5 600 I s Cutoff time Teo 10 800 min Fixing of the ranges based on a large number of runs has been done to avoid too many impossible combinations and corresponding error messages For all practical purposes the indicated ranges of the individual parameters will be more than sufficient If you combine extreme values of the various parame ters you may not get a result In that case BASDEV will flash you a message on the screen indicating
21. s reei the minimum infiltrated depth is 95 mm and the storage efficiency is still 100 per cent The application efficiency is good 87 per cent These results are acceptable Table 5 6 was also made with BASDEV as outlined above Once you are famil iar with the foregoing basic elements of working with the program you can solve the more elaborate problems presented in Chapter 8 These concern sev eral sets of runs with which various relationships can be established They illustrate the further possibilities of BASDEV as well as providing a deeper insight into the complex nature of the basin irrigation process 66
22. t in addition to the basin dimensions and the flow rate Thus all design variables are input which means that the required depth at the end of the field will usually not be achieved and under and or over irrigation will occur The main indicator is the minimum infiltrated depth occurring at the far end of the field It is therefore given as the first output parameter followed by the primary performance indicators and infiltrated depths This mode is most suitable for a performance evaluation of an existing level basin irrigation sys tem and for testing the performance sensitivity to a change in the field param eters Together Modes 3 and 4 constitute the core of BASDEV 53 5 2 Input windows When a calculation mode has been selected BASDEV will display two win dows on your screen for data entry Field Parameters and Input Decision Variables The input data to be provided in the two windows are summarised in Table 5 2 Usually you will only need to change the values of the field parameters to carry out sensitivity analyses after you have obtained satisfac tory results in Mode 3 or 4 see Chapter 4 Section 3 2 Calculation examples can be found in Chapter 8 Section 1 1 5 2 1 Field parameters Infiltration Upon selection of the Modified SCS families type of infiltration data BAS DEV will use the intake families as discussed in Chapter 3 Section 1 1 One of the eight families can be chosen If a wrong number is typed an
23. umber of practical assumptions on conditions that require fulfilment These may also restrict the use of BAS DEV We therefore briefly discuss the theoretical assumptions and the practi cal limitations of the use of BASDEV for design operation or evaluation of a level basin surface irrigation system As explained in Appendix A the model assumes that The modified Eulerian cell approach with the modified zero inertia model is appropriate for simulating the advance phase The modified Manning equation and flow resistance coefficients are suffi ciently accurate in describing the surface flow component The infiltration characteristics and the approximation of infiltration pro files are sufficiently accurate in describing the infiltration component The numerical solution procedures are sufficiently accurate in establishing the volume balances The simplifications of storage and recession phase are realistic Apart from these more theoretical assumptions related to the algorithm and its solutions ie accepting the model as it is there are a number of practical conditions that should be fulfilled The most important are the following There is no surface runoff This is a reasonable assumption which is achieved by ensuring that the bunds all around the basin are sufficiently high and by working with reasonable water depths Inflow is evenly distributed over the width The program works with unit flows wher
24. ure 5 2 Performance output for Basdev the program ensures In Mode 4 the application efficiency and the distribu tion uniformity are usually not the same and hence both are shown The key F3 shows you two graphs with the main results the upper one shows the cutoff time and the advance time in relation to field distance and Table 5 4 Output results for the Basdev calculation modes Qutput parameters Mode 1 Mode 2 Mode 3 Mode 4 Design variables Basin length Basin width o Flow rate 0 Cutoff time o 9 o Primary performance indicators Application efficiency E D o Distribution uniformity 0 Storage efficiency 0 Infiltrated depths Minimum infiltrated depth o a o Maximum infiltrated depth o o E Average applied depth 0 0 o o Under irrigation Uength depth 0 Over irrigation length depth 0 Time variables Advance time o 0 Recession time a 58 time min 0 13 25 38 distance m 50 0 atalala aletale ateta eatea pelete e a eye ere era etu orafa u eu eta ata a atera a e eS Tatala eta eta ela eta eta ata E E E ER acl tee ac oH SE NOES z pupp RENE 44 PENEDO L I D D I I D I I TTT Ln EE SSSSSS Cen a ee a ale ae ee ee ee ee ea ee e o o to enp a p e a en ee o e a e be p e a ene G EEEE eRe Ce eC Se 66 eR EE N Be E E o j req over irrigation under irrigation Figure 5 3 Graphic output of advance curve and infiltration profile the lower one shows the infiltrated depths along the
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