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Testing of the IGARF1 v4 spreadsheet tool for assessing the impacts

1. El Microsoft Excel IGARF1v4_Test4 uls 2 6 x Eie Edt view Insert Format Tools Data Window Help ale x JOSE S6RY SBAS O 4 gt A My ara zo B zu x dist_scale v IF rdf_scl_check 0 MIN 20000 MAX 100 SORT Transmissivity MAX ABS dista2 ABS distal i 4 Storage_coetficient max_lam rdf_scl_check A B C D l J K 1 River Depletion Factor Sheet for River 2 2 Numerical Parameters please refer to manual for a detailed description ENVIRONMENT 3 Parameters for the Fourier Transform AGENCY 4 Power CL ____Fscate Factor ea
2. 26 Humerical solution for specified reach Numerical solution for infinite reach Analytical Solution for Steady State flows over an infinite reach 27 River 1 0 1433 River 1 0 5000 River 1 0 5000 28 River 2 0 1433 River 2 0 5000 River 2 0 5000 29 T 0 2866 Total 1 0000 Total 1 0000 z l4 4 gt bi Periodic Abstraction Periodic Abstraction Table Impact of Pumping Test _ _calculations_ Audit rdf functions rdf functions 2_ dal IT draw Py G autoshaes SOB 4M O 4 A EE Ready Calculate i es NUM Figure 17 Test 1 rdf functions sheet Figure 18 El Microsoft Excel IGARF1v4_Test1 xls S ile Edit View Insert Format Tools Data window Help la x 61 x JOSsE 6RY sBRSloO a A1 hd A 2 anal Evolution of River Flow Depletion WARNING The impact of the two river system is not being resolved and the single river solutions for each river are being returned Refer to the Numerical Parameters section Evolution of River Flow Depletion Click on the chart to return to the Data Sheet on the rdf functions worksheet to determine whether an inappropria
3. File Edit View Insert Format Tools Data Window Help jose ESR smeo ae fz i Alara zuo se 7 T B5 M A B c D J K ica 1 River Depletion Factor Sheet for River 2 2 Numerical Parameters please refer to manual for a detailed description ENVIRONMENT 3 Parameters for the Fourier Transform AGENCY 4 Power Scale Factor Scale Factor for drawdown E 5 6 Fourier Transform Output z Examples of the impact of the Scale Factor on the Fourier Transform output a os a 05 10 River 2 11 24 12 o3 t River 1 133 34 2 15 o 16 o 17 o 500000 1000000 1500000 Scale factor too low Acceptable scale factor Scale factor too high 18 19 20 WARNING The impact of the two river system is not being resolved and the single river solutions for each river are being returned Refer to Fourier Transform Output 21 chart to determine whether an inappropriate scale factor is being used 22 a 24 COMPARISON OF IMPACTS FROM NUMERICAL AND ANALYTICAL SOLUTIONS THE ANALYTICAL SOLUTION IS THE LIMITING CASE 25 Red cells indicate that the numerical solution exceeds the analytical solution Refer to the chart above to determine whether an appropriate scale factor is being used 26 Humerical solution for specified reach Numerical sol
4. Dur Pum Upstream limit Downstream li Calculate Now i ENVIRONMENT Last calculated at AGENCY Last saved at 7 Y y 0 Dale AS ins ee 5 i414 gt i Data Sheet Evolution of River Depletion Profile of River Depletion Time Drawdown Drawdown Contours Periodic Abstraction Perioc tT crows R G autoshopess SS OR AB O 4 A eO Ready Calculate lI I a NUM Figure 3 Data Sheet of IGARF model used for ZOOMQ3D comparison 1 Figures 4 to 6 show that there is close agreement between the analytical and numerical model solutions for each of the three types of impact plotted for this first comparison Figure 4 and 5 show the s shaped nature of the time drawdown and evolution of river depletion curves when plotted on a log time axis with the system approaching steady state after approximately 100 days The time drawdown and evolution of river depletion curves are very similar but small differences are apparent at early times i e less than 5 days after the start of pumping This is due to the numerical model being less accurate at the start of the simulation due to the use of a relatively coarse one day time step Figure 6 shows the profiles of river depletion after 200 days and obviously illustrates that the greatest impact on the river is closest to the
5. Data Sheet Evolution of River ion Profile of River ion Time Drawdown Drawdown Contours Periodi 4 mie orem gt Ty Anosh Ss IO 4M Oo s A S oam Ready Calculate a Cr Nom Figure 28 Data Sheet for Test 5 spreadsheet model The changes to the model parameters and their effects on the solution are listed in Table 3 In general when simulating this low transmissivity and storage system in which the pumped well is close to the river few warnings are presented to the user that cannot be corrected by adjusting the Scale Factor In this case the numerical solution process only failed to produce adequate results when an extreme and unrealistic parameter value was used for the river bed sediment thickness i e 0 001 m This is not likely to used in practice but if required this warning could be circumvented by using a high river bed hydraulic conductivity instead The second problem that was identified was the simulation of an irregular river depletion profile 10 days after the cessation of pumping This is shown in Figure 29 Whilst this is not accurate the depletion rates at this time are so small that it is not of great importance 24 Table 3 Original parameter set shown in Figure 28 Difference from original parameter data set Increase storage coefficient to 0 1 Saturated thickness increased and decreased Depth of river increased and decreased River bed sediment thickness increased Sediment thickness reduced to 0 0
6. and by altering the geometry and hydraulic characteristics of the aquifer The tests in this section represent a relatively small number of examples but illustrate some of the problems encountered during the use of the tool Groundwater systems are modelled which both broadly approximate UK aquifers types and which include features that incorporate extreme parameters or represent untypical situations 5 1 TEST 1 TWO HUNT RIVERS 10KM APART ABSTRACTION BOREHOLE HALF WAY BETWEEN RIVERS This model includes an abstraction well that is located half way between two Hunt type rivers The distance between the rivers is 10km and the parameters assigned to the aquifer approximate a high transmissivity low storage system i e a transmissivity of 1000 m day and a storage coefficient of 1 The model data set is shown in Figure 16 The evolution of river depletion is monitored over the reaches from 2 km upstream to 2 km downstream of the pumped well El Microsoft Excel IGARF1v4_Test1 xls 18 xj JG Eile Edit View Insert Format Tools Data Window Help laj xi Deasy BaS 5 o B gt A i jaa 22 e z UlEP22m 9 e 2 o A 2 A M Project name Test 1 a Conceptual Model Parameters Abstraction rate Compensation Transmissivity m2 d m3id returns m3 d Abstraction well laj a ya ver jell 1 Sel ZE A Conceptual Model bd iver 2 Hunt Aquife r Width River aquifer contact length Width Sedime
7. jul 100 m aug 5m sep oct h Dur Pumping rate for Upstream limit Downstream lii Calculate Now ENVIRONMENT m Last calculated at AGENCY Monitoring well location y m Last saved at 19 05 2004 16 03 14 gt DIN User information Model Selection Data Iny yam Data Sheet Evolution of River Depletion Profile of River Depletion 4 mi Jows Ty G Atoshepess gt amp OR AB O 4 A S eu Ready Calculate a Figure 30 Data sheet for Test 6 model 27 5 8 TEST 7 PUMPED WELL BETWEEN HUNT AND HANTUSH TYPE RIVERS In this test a spreadsheet model is constructed using the data shown in Figure 31 In this system the pumped well is located 4 km from a Hunt type river and 4 km from a Hantush type river The initial model has a high transmissivity of 2000 m day and storage of 1 however as in Test 5 each of the aquifer and river parameters is adjusted in turn to examine the effect on the robustness of the solution process i e to investigate when and how often warning messages are presented to the user Ea Microsoft Excel IGARFiv4_Test7 xls alal x 2 Eile Edit View Insert Format Tools Data Window Help l xi rA Er E E My 2 ara 72 v B z u Ele 2 E 2 0 A 2 Al fad Project name TOI fame lest a ion well Well 1 Conceptual Model Parameters Abstraction rate Compensation na Mot i m3id returns m3 d Sel ew VEF i Conceptual Model EEY EN 4 5m 20 m River aquifer contact leng
8. m3id Project Name Test 1 River 2 At 5000m River 1 At 5000m 200 Abstraction Well Well 1 Name 0 T T T T T T T T ENA 0 10 20 30 40 50 60 70 80 90 100 Time d River 1 River 2 ENVIRONMENT AGENCY These data have been calculated using a two river solution The River 2 is a Theis River The River 1 is a Theis River 14141 gt l Dats Input Diagram Data Sheet Evolution of River Depletion Profile of River Depletion Time Drawdown Drawdown Contours Periodi mil orawy Ty G autoshessy gt n AC IOR AB AA ERM Ready Calculate I pem f NUM p Figure 24 Test 3 Evolution of River Flow Depletion sheet 21 5 5 TEST 4 TWO HUNT RIVERS 4 KM APART ABSTRACTION BOREHOLE HALF WAY BETWEEN RIVERS This model again included an abstraction well that is located half way between two Hunt type rivers The distance between the rivers is 10 km and the parameters assigned to the aquifer approximate a low transmissivity high storage aquifer system i e transmissivity of 100 m day and storage coefficient of 15 The model Data Sheet is shown in Figure 25 The evolution of river depletion is monitored over the reaches from 2 km upstream to 2 km downstream of the pumped well As with Test 1 and 2 the Scale Factor and Power parameter were adjusted but it was not possible to stop the warning relat
9. 2 British BGS Geological Survey 1835 NATURAL ENVIRONMENT RESEARCH COUNCIL Testing of the IGARF1 v4 spreadsheet tool for assessing the impacts of groundwater abstraction on river flows Groundwater Systems amp Water Quality Commissioned Report CRO4 095N The National Grid and other Ordnance Survey data are used with the permission of the Controller of Her Majesty s Stationery Office Ordnance Survey licence number GD 272191 1999 Key words IGARF groundwater abstraction river flows Bibliographical reference JACKSON C R 2004 Testing of the IGARF1 v4 spreadsheet tool for assessing the impacts of groundwater abstraction on river flows British Geological Survey Commissioned Report CR 04 095N 32pp NERC 2004 BRITISH GEOLOGICAL SURVEY COMMISSIONED REPORT CR 04 095N Testing of the IGARF1 v4 spreadsheet tool for assessing the impacts of groundwater abstraction on river flows C R Jackson Keyworth Nottingham British Geological Survey 2004 BRITISH GEOLOGICAL SURVEY The full range of Survey publications is available from the BGS Sales Desks at Nottingham and Edinburgh see contact details below or shop online at www thebgs co uk The London Information Office maintains a reference collection of BGS publications including maps for consultation The Survey publishes an annual catalogue of its maps and other publications this catalogue is available from any of the BGS Sales Desks The Briti
10. Av 74 B z u S e B 4 A 2 Al bd River Depletion Factor Sheet for River A B c iD I J K E 1 River Depletion Factor Sheet for River 2 2 Numerical Parameters please refer to manual for a detailed description ENVIRONMENT 3 Parameters for the Fourier Transform AGENCY 4 Power OfScale Factor 5 6 Fourier Transform Output 7 8 o6 g 05 10 River 2 m 24 12 03 River 1 JE 14 02 45 01 16 o 17 o 100000 200000 300000 Scale factor too high 18 WARNING The data shown in the Fourier Transform Output chart may be falling to zero too rapidly Observe the impact of increasing the Scale Factor or decreasing the Power on the model outputs WARNING The impact of the two river system is not being resolved and the single river solutions for each river are being returned Refer to Fourier Transform Output chart to determine whether an inappropriate scale factor is being used COMPARISON OF IMPACTS FROM NUMERICAL AND ANALYTICAL SOLUTIONS THE ANALYTICAL SOLUTION IS THE LIMITING CASE Red cells indicate that the numerical solution exceeds the analytical solution Refer to the chart above to determine whether an appropriate scale factor is being used
11. Factor for drawdown 5 6 Fourier Transform Output Z Examples of the impact of the Scale Factor on the Fourier Transform output 8 o6 os 10 River 2 41 04 12 03 te River 1 13 44 2 45 01 16 of 17 O 5E 06 1E 07 2E 07 2E 07 3E 07 Scale factor too low Acceptable scale factor Scale factor too high 18 i 20 WARNING The impact of the two river system is not being resolved and the single river solutions for each river are being returned Refer to Fourier Transform Output 21 chart to determine whether an inappropriate scale factor is being used 22 a 24 COMPARISON OF IMPACTS FROM NUMERICAL AND ANALYTICAL SOLUTIONS THE ANALYTICAL SOLUTION IS THE LIMITING CASE 25 Red cells indicate that the numerical solution exceeds the analytical solution Refer to the chart above to determine whether an appropriate scale factor is being used 26 Humerical solution for specified reach Numerical solution for infinite reach Analytical Solution for Steady State flows over an infinite reach 27 River 1 0 0010 River 1 0 5000 River 4 0 5000 28 River 2 0 0010 River 2 0 5000 River 2 0 5000 0 0020 Total 1 0000 Total 1 0000 a I4 4 piZ Periodic Abstraction Periodic Abstraction Table Impact of Pumping Test _ calculations Audit rdf functions rdf functions 2_ dal tT Draw gt R CG Autoshapesy 5 a Ready Calculate 1 Ea NUM Figure 27 Test 4 rdf functions sheet 23 5 6 TEST 5 HANTUSH RIVER WELL NO FL
12. Microsoft Excel calculates the effect that a constant or periodic groundwater abstraction has on a groundwater system containing one or two straight line rivers The testing involves the simulation of a number of different aquifer configurations to examine if and when the tool has difficulty in calculating a solution In addition to examining the robustness of the spreadsheet a number of comparisons are made with a numerical model There is close agreement between the results produced by the numerical model and the IGARF tool in these comparisons Whilst the testing has shown that the spreadsheet is a Powerful and easy to use modelling application that generally produces accurate results rapidly a number of problems have been encountered One problem appears to relate to the execution of the dynamic link library dll and it is suspected that an error in the dll can cause the tool to crash This has occurred approximately 6 times during this investigation and appears to be due to memory referencing or allocation errors However it is not absolutely certain that the error lies within the dll and it could be a problem with the code contained in an Excel macro This problem should be resolved before the tool is released to organisations external to the Environment Agency Four models have been constructed using both the IGARF1 v4 spreadsheet and a numerical model and a comparison has been made between the results of each The results are in close agree
13. The example described in Appendix C 4 of the IGARF1 v4 User Manual in which an abstraction borehole is pumped at a rate of 1000 m day and which is 10 m from a Theis type river and 100 m from a Hunt type river is reproduced A comparative plot is produced for the profile of river depletion after 100 days of pumping 4 2 COMPARISON 1 In this comparison a pumped well is located midway between two Hunt type rivers which are 4km apart The hydraulic parameters assigned to the model are broadly representative of a Chalk aquifer i e a relatively high transmissivity of 1000 m day and a relatively low storage coefficient of 1 are applied The abstraction borehole pumps at a constant rate of 10 000 m day for 200 days The full parameter data set is illustrated in Figure 3 which shows the Data Sheet for the IGARF model The numerical model is 20 km square and has a 125 m square mesh The abstraction borehole is located in the centre of the model The rivers are 2 km from the pumped well and are assigned the same parameters as those input to the IGARF spreadsheet A one day time step is used to simulate the system Three charts are produced Figures 4 to 6 which show the comparison between the analytical and numerical model for e the time drawdown at an observation well halfway between the well and one of the rivers with time shown on a log scale e the evolution of river depletion over the reach 2 km upstream to 2 km downstrea
14. comparing simulated results with those presented in the User Manual 3 Bugs amp error hunting 3 1 BUGI This was encountered when using the version of the spreadsheet containing the reporting facility Whilst following the River Otter case study and examining the time drawdown curves discussed in Section 5 2 7 of the User Manual the following error occurred e After having previously followed the example to the end of Section 5 2 7 successfully the x axis maximum of the time drawdown curve was changed a few times It was then changed back to 180 days and the Calculate Now button was pressed again It then appeared that the code possibly contained in the dll could not reference the required area of memory A Windows pop up error message was presented specifying this error which gave the option to debug On pressing OK to skip debugging Excel was shut down A number of attempts were made to repeat this error by following the same steps but the problem did not recur The same problem was encountered on pressing Calculate Now after having filled in the Data Sheet to run the Example C 7 in Appendix C of the User Manual Figure 1 This problem was not encountered when a second attempt was made to run the model However this error did recur approximately five times generally when the Calculate Now button was pressed E3 Microsoft Excel IGARF_Otter xls l j xi E fle Edit view Insert Format Tools Data window Help la x JOS E SRY s B
15. is a repeat of Test 1 but with Hantush type rivers used instead of Hunt type rivers All other model parameters are the same As with Test 1 the Scale Factor and Power parameter were adjusted but it was not possible to stop the warning relating to the returning of the single river solution for both rivers from appearing A Scale Factor of 50 000 was required to stop the Fourier Series Output chart from falling to zero too rapidly Figure 20 This warning message still occurred when the reach length over which the evolution of river depletion was calculated was reduced to 100 m upstream and downstream of the abstraction borehole as shown in Figure 21 Ea Microsoft Excel IGARF1v4_Test2 xls laj x Ele gdt View Insert Format Tools Data Window Help la x PEVE TECNA E i Flan 2 e z u E Ses alee oa 2 A1 X Project name roj lame Test2 a i n well Conceptual Model Parameters Abstraction rate Compensation Vay ity m3id returns m3 d na Sel Conceptual Model Well 1 t River aquifer contact length Depth Sediment thickness a Sediment hydraulic conductivity of well to river Depth lt gman E River aquifer contact length Depth 1 2 The drawdown at the well is greater than 50 of the 2 Dur effective saturated thickness of the aquifer This Pumping rate for may affect the validity of the solution Upstream limit Downstream Ii Calculate Now ENVIRONMENT Last calculated at AGENCY Monit
16. well The two profiles of river depletion are also in very close agreement and there are no visually discernible differences between the two model plots Figure 4 Figure 5 Figure 6 18 Time drawdown at 1000m 0m 1 6 4 IGARFI v4 ZOOM 0 8 4 0 6 5 Drawdown 1km to east of well 0 4 4 0 2 4 0 1 1 10 100 1000 Time days Time drawdowns curves for ZOOMQ3D comparison 1 River depletion over reach 2000 to 2000 m 3500 5 IGARF1 v4 3000 4 x ZOOM 3 2500 4 E 2000 4 E amp 15004 3 2 1000 4 a4 500 4 1 10 100 1000 Time days Evolution of river depletion curves for ZOOMQ3D comparison 1 Profile of river depletion at time 200 days IGARF1 v4 14 x ZOOM 0 8 5 3 Depletion rate m day m 0 6 xx x 0 4 4 x xX 0 2 7 0 om T T T T T T T T 10000 8000 6000 4000 2000 0 2000 4000 6000 8000 10000 Distance downstream of well m Profile of river depletion for ZOOMQ3D comparison 1 4 3 COMPARISON 2 This comparison uses the same model as that used for comparison 1 However in this simulation the abstraction borehole pumps periodically The well pumps for six months between May and October at a rate of 10 000 m day The full parameter data set is illustrated in Figure 7 which shows the Data Sheet for the IGARF model The numerical model is the same as that used in com
17. 1 m Sediment thickness reduced to 0 001 m Reduce hydraulic conductivity of river bed to 10 4 mday Distance of well to river increase to 1 km Reduce distance to no flow boundary to 100 m Increase abstraction to 5000 m day Reduce abstraction to 50 m day Calculate evolution of river depletion for reach from 100 m to 100 m Calculate evolution of river depletion for reach from 5000 m to 5000 m Calculate profile of river depletion 1 day after start of pumping Calculate profile of river depletion 110 days after start of pumping Time at which to calculate contours increased and decreased Location of monitoring well moved perpendicular to river along line of well Summary of Test 5 model parameters adjustment process and warnings Warning produced relating to too rapid fall of Fourier Series Output Easily corrected by increasing Scale Factor Results Warnings persist No warnings errors observed No warnings errors observed No warnings errors observed Warnings are easily resolved by adjusting the Scale Factor but river becomes disconnected Warnings presented in which abstracting more from river than abstraction corrected using Scale Factor Warnings presented in which abstracting more from river than abstraction Could not correct using Scale Factor and Power parameters Numerical accuracy warnings occur but are easily resolved by adjusting Scale Factor River becomes d
18. 93 411501 www nerc ac uk Contents Summary 1 Introduction 2 User Manual case study of the River Otter 3 Bugs amp error hunting 3 1 Bugl 3 2 Bug2 3 3 Bug 3 4 Comparison with numerical model 4 1 Background 4 2 Comparison 1 4 3 Comparison 2 4 4 Comparison 3 4 5 Comparison 4 5 Numerical accuracy of the spreadsheet 5 1 Test 1 Two Hunt rivers 10km apart abstraction borehole half way between rivers 5 2 Sensitivity analysis using Test 1 5 3 Test 2 Two Hantush rivers 10km apart abstraction borehole half way between rivers 5 4 Test 3 Two Theis rivers 10km apart abstraction borehole half way between rivers 5 5 Test 4 Two Hunt rivers 4 km apart abstraction borehole half way between rivers 5 6 Test 5 Hantush river well no flow boundary system 5 7 Test 6 Well between Two Hunt type rivers 5 8 Test 7 Pumped well between Hunt and Hantush type rivers 6 Conclusions References iv RW WwW O UUM A 12 14 14 17 18 20 22 24 27 28 30 32 FIGURES Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 Figure 28 Figure 29 Figure 30 Figure 31 Error during running of Example C 7 in Appendix C oo eeeeceeeeseeneeeeeteeneeenees 3 Screen dump showing bu
19. HING The impact of the two river system is not being resolved and the single river solutions for each river are being returned Refer to the Numerical Parameters section jon the rdf functions worksheet to determine whether an inappropriate scale factor is being used Chart Properties x axis minimum 0 d River depletion over reach 10 m to 10 m m3id x axis maximum 2000 d Upstream limit of reach evaluated m Downstream limit of reach evaluated 3 0 07 E 0 06 he parameters used to calculate e hese data have not been saved in 8 0 05 ja report file 2 Ey 0 04 go 5 00 Project Name Test 4 0 02 River 2 At 5000m River 1 At 5000m 0 01 Abstraction Well Well 1 Name 0 T T T T Calculate Now 0 200 400 600 800 41000 41200 1400 1600 1800 2000 Time d River 1 River 2 These data have been calculated using a two river solution The River 2 is a Hunt River The ENVIRONMENT River 1 is a Hunt River AGENCY l4 T4 Pi User Information Conceptual Model Selection Data Input Diagram Data Sheet Evolution of River Depletion Profile of River Depletion wi orem R i autoshapes s 48 o 4 A S EO Ready Calculate a TT Nom Td Figure 26 Test 4 Evolution of River Flow Depletion sheet
20. OW BOUNDARY SYSTEM In this test an IGARF spreadsheet model is constructed using the data shown in Figure 28 In this system the pumped well is located 10 m from a Hunt type river and km from a no flow boundary The initial model has a low transmissivity of 50 m day and low storage of 0 1 however each of the aquifer and river parameters is adjusted in turn to examine the effect on the robustness of the solution process i e to investigate when and how often warning messages are presented to the user El Microsoft Excel IGARF1v4 no report xls Read Only Eile Edit View Insert Format Tools Data window Help JOSE S6RY SBAS O o B gt A hy 2 Ara E54 pe Pro name Test5 Al ipn bad Well 1 mcrae Model Parameters Compensation na ransmissivity 50 m2id m3id returns m3 d Storage coefficient 0 001 Effective saturated thickness 100 m Depth 5m Width 5m Sel R Conceptual Model River aquifer contact length Width 5m Sediment thickness 4 River 1 Hunt Aquifer Er Sediment hydraulic conductivity A _ Distance of well to river not used f not used notused not used i 2 not used Distance of well to noflow boundary 1000 1000 01 n Tian 100 d n Panini rate fori Depletion Upstream limit Downstream lis de Calculate Now ENVIRONMENT A Last calculated at AGENCY Monitoring well location y Last saved at 30 03 2004 17 22 ay J F M141 pif Data put Diagram
21. Y SEs 5 Storage coefficient 0 01 jan Conceptual Model bd Effective saturated thickness 100 m feb 7 Depth 41m mar ar E width 5m apr ayes River aquifer contact length Width 5m may 2g ra N Sediment thickness o1m jun B eai a E Sediment hydraulic conductivity 1 00 01 mid jul Distance of well to river 2000 m 2 aug d z Depth 1m sep i T T E width sm oct i gt a River aquifer contact length Width 51 S nov T Sediment thickness orm 3 dec L 2 Sediment hydraulic conductivity 1 00E 01 ma geau Distance of well to river 200m 10000 0 1 il 2 aa 200 y fei h 3 Dur Pum Upstream limit Downstream li a Calculate Now ENVIRONMENT m Last calculated at AGENCY Ea Last saved at FT nae 4 4 gt PIN User Information Conceptual Model Selection Data Input Diagram Data Sheet Evolution of River Depletion Profile of River Depletion i dram gt ty G autoshapes gt SOR AB O 4 A S Rag Ready Calculate a NUM Figure 7 Data Sheet of IGARF model used for ZOOMQ3D comparison 2 The comparison between the two models for the evolution of river depletion is shown in Figure 8 This again shows that the two models are in good agreement In particular the rising and falling limbs of the curve are in close agreement However the numerical model does simulate slightly greater depletion rates towards the end of the six month period of abstraction The exac
22. au sez o A M River Depletion Factor Sheet for River A B c D J K ica 1 River Depletion Factor Sheet for River 2 2 Numerical Parameters please refer to manual for a detailed description ENVIRONMENT 3 Parameters for the Fourier Transform AGENCY 4 Power CL dscate Factor Scale Factor for drawdown E 5 6 Fourier Transform Output z Examples of the impact of the Scale Factor on the Fourier Transform output 8 os 2 os 10 River 2 11 24 12 03 te River 1 33 34 2 15 o 16 o 17 o 500000 1000000 1500000 Scale factor too low Acceptable scale factor Scale factor too high 18 19 20 WARNING The impact of the two river system is not being resolved and the single river solutions for each river are being returned Refer to Fourier Transform Output 21 chart to determine whether an inappropriate scale factor is being used 22 a 24 COMPARISON OF IMPACTS FROM NUMERICAL AND ANALYTICAL SOLUTIONS THE ANALYTICAL SOLUTION IS THE LIMITING CASE 25 Red cells indicate that the numerical solution exceeds the analytical solution Refer to the chart above to determine whether an appropriate scale factor is being used 26 Humerical solution for specified reach Numerical solution for infinite reach Analytical Solution for Steady State flows over an infinite reach 27 River 1 0 1215 River 1 0 5000 River 1 0 5000 28 River 2 0 1215 River 2 0 5000 River 2 0 5000 0 2430 Total 1 0000 Total 1 0000 z i4 4 gt gt I Periodic Abstraction Periodic Abs
23. calculated using a single river and no flow boundary solution The ENVIRONMENT River 1 is a Hunt River If the data presented on this chart are oscilliating you may need to increase the Power parameter Refer to the User Manual for further information a 14 4 gt pif Data Sheet Evolution of River Depletion Profile of River Depletion Time Drawdown Drawdown Contours Periodic Abstraction Perioc 4 Draw gt Dy G Autoshapes a CO4 o 4 A ea Ready Calculate i TT Nom Figure 29 Irregular profile of profile of river depletion during use of Test 5 model 26 5 7 TEST 6 WELL BETWEEN TWO HUNT TYPE RIVERS In this test an IGARF spreadsheet model is constructed using the data shown in Figure 30 This is the same system as described in the previous example but with the no flow boundary being replaced by a second Hunt type river The pumped well is located 100 m from both rivers Again the aquifer has a low transmissivity of 50 m day and low storage of 0 1 A single run was performed to see if the introduction of a second Hunt type river caused problem to the solution process This was not found to be the case E Microsoft Excel IGARF1v4_Test6 xls ile Edit View Insert Format Tools Data Window Help JDSE S6RY SBAaS o gt A fy jaa Al E Project name rol Test6 well nai i Sel PET N Conceptual Model x Well 1 01 m 3 jun 1 00E 01 mid
24. e River 1 is a Hantush River AGENCY 4 4 gt bI User Information Conceptual Model Selection Data Input Diagram Data Sheet Evolution of River Depletion Profile of River Depletion ow R amp AutoShapes a og4m gt 24 4A Sagq Ready Calculate I Ea INUM Figure 21 Test 2 Evolution of River Flow Depletion sheet 19 5 4 TEST 3 TWO THEIS RIVERS 10KM APART ABSTRACTION BOREHOLE HALF WAY BETWEEN RIVERS Test 3 is a repeat of Test 1 but with Theis type rivers used instead of Hunt type rivers All other model parameters are the same Again as with Test 1 the Scale Factor and Power parameter were adjusted but it was not possible to stop the warning relating to the returning of the single river solution for both rivers from appearing The Data Sheet and model output are shown in Figures 22 to 24 El Microsoft Excel IGARF1v4_Test3 xls laj x E ie Edt View Insert Format Tools Data Window Help lalx JOSOE S6AY sSBRSlo o B A i 2 ara ao ae PDE E e gt s gt erA gt 3 2 v Test 3 t ion welll Aweit 4 Conceptual Model Parameters Abstraction rate Compensation T nai Wye A Transmissivity 1000 m2id m3id returns m3 d Sel I NY festa Storage coefficient 0 01 Conceptual Model bd Effect
25. e is pumped at a rate of 1000 m day which is 10 m from a Theis type river and 100 m from a Hunt type river The full parameter data set is illustrated in Figure 13 which shows the Data Sheet for the IGARF model The numerical model is shown in Figure 14 The model is 4 km square and in the area of interest around the well and rivers the mesh spacing is 10 m square As discussed in Appendix C of the User Manual the spreadsheet cannot calculate the evolution of river depletion for this scenario but can calculate the profile of river depletion after 100 days of pumping Consequently in this comparison only one comparative plot is produced which is the profile of river depletion after 100 days of pumping This illustrates that in this relatively low transmissivity and low storage shallow aquifer in which the pumped well is close to two rivers there is close agreement between the two models Figure 15 El Microsoft Excel IGARF1 4_Z00M4 xls laj x Eile Edit View Insert Format Tools Data Window Help 18 x JOSE S6RY SBBS o fH fy gt anal K56 bd Project name Zoom comparison 4 nwo Conceptual Model Parameters Abstraction rate Compensation na kod 5 Transmissivity m3id returns m3 d Sel y Well 1 N Conceptual Model i i 2 Theis Aqui hea 3 4 Sediment hydraulic conductivity Distance of well to river WARNING the River 1 becomes disconnected by the end of pumping from the abstract
26. er parameters on the rdf functions sheet had to be adjusted to resolve the warning messages that are presented after the solution is calculated In most cases the warning messages can be resolved quickly generally by adjusting the Scale Factor parameter only However for some models it was not possible to resolve the warning messages by adjusting either or both of the Scale Factor and Power parameters The most frequently occurring warning that could not be resolved was WARNING The impact of the two river system is not being resolved and the single river solutions for each river are being returned Refer to the Numerical Parameters section on the rdf functions worksheet to determine whether an inappropriate Scale Factor is being used 30 This warning relates to the evolution of river depletion over time and always occurred in the models containing a well located half way between two rivers see sections 5 1 to 5 4 and 5 8 in e an aquifer with transmissivity of 1000 m day and a storage coefficient of 1 with rivers 10 km apart e an aquifer with transmissivity of 100 m day and a storage coefficient of 15 with river 10 km apart These are realistic parameters for UK aquifers but the message also occurred in the model of e an aquifer with transmissivity of 2000 m day and a storage coefficient of 10 with river 8 km apart see Section 5 8 Numerous other aquifer and river well configurations have been s
27. es o o Flim ara u E als x e B O A Otter Case Study T ion well Conceptual Model Parameters Abstraction rate nal Po A Transmissivity 100 m2id m3id Sel we Z Storage coefficient 0 0001 Conceptual Model Effective saturated thickness 10 m j h Depth 5m Width 5m River aquifer contact length Width 5m sediment thickness eim Prod BH 4 Sediment hydraulic conductivity 1 00E 01 mid Distance of well to river 10 m not used m The instruction at 0x053e53e6 referenced memory at 0x0480e018 The memory could not be read Click on OK to terminate the program Click on CANCEL to debug the program Thames evern The drawdown at the well is greater than 50 of the Se Dur effective saturated thickness of the aquifer This he Pui may affect the validity of the solution ic Upstream limit Create Report ENVIRONMENT EEA AGENCY m ai SN itt gt M I4 41 gt gt l Data Sheet Evolution of River Depletion Profile of River Depletion Time Drawdown Drawdown Contours Periodic Abstraction Perioc IF orn G autoshepes a OE 4il o J A eu Calculating Cells 10 start 4 S A noveu ijicaRF_1_v4_e Gyicarrs Microsoft Excel Microsoft excel a OINML SALQOQ D 14 47 Figure 1 Error during running of Example C 7 in Appendix C 3 2 BUG2 This was encountered when using the version of the spreadsheet containi
28. g 2 anria a A E T EE 4 Data Sheet of IGARF model used for ZOOMQ3D comparison 1 ceeeeeeeees 6 Time drawdowns curves for ZOOMQ3D comparison l o eeeceeseesseeeteeeteeeseees 7 Evolution of river depletion curves for ZOOMQ3D comparison 1 seers 7 Profile of river depletion for ZOOMQ3D comparison 1 ou ce eeeeeeseeeeeteeneeenees 7 Data Sheet of IGARF model used for ZOOMQ3D comparison 2 c ceseeeees 8 Evolution of river depletion curves for ZOOMQ3D comparison 2 ceeeeees 9 Data Sheet of IGARF model used for ZOOMQ3D comparison 3 seeseeeee 10 Profiles of river depletion for ZOOMQ3D comparison 3 0 0 eceeeeeeseeeseeeeeneees 11 Time drawdown curves for ZOOMQ3D comparison 3 ccceesseesseesteeeteeeseeeees 11 Evolution of river depletion curves for ZOOMQ3D comparison 3 eeee 11 Data Sheet of IGARF model used for ZOOMQ3D comparison 4 ceeeeeeee 12 ZOOMQ3D model for comparison 4 occ eeeceeseessceseceeseessecsseceeeceeeceeseeeseeenseeaes 13 Profiles of river depletion for ZOOMQ3D comparison 4 00 eeeeceeeeeseenreeeeeeeees 13 Test l AAAS TS i asl eee ade roa cas EE tuna or or vients a ET 14 Test rdf functions sheets a neared eatin 15 Test 1 Evolution of River Depletion sheet cccccccesssesseesteeetseesseesteeeteeeseeeees 16 Test 2 Data Shetani oaae aa E args ates rera E EE E Snide eiar EE 18 Test 2 rdf f netions Sheet viscs cats nips carta ea aw on ea aati 19 Test 2 Evolution of R
29. imulated for which no warnings or errors were observed except when setting extreme parameter values e g the river sediment thickness to 10 m in Test 5 Section 5 6 However in Test 7 Section 5 8 it was not possible to resolve the warning messages when the river bed sediment hydraulic conductivity of the two rivers was reduced to 10 mday This is not an unrealistic value for river bed permeability Whilst the numerical warnings occurred frequently the appropriate warnings were always presented at the appropriate time These warnings are well presented and make it easy for the user to attempt solve the problem However in terms of the ease of use of the tool perhaps one improvement that could be made would be to implement a button on the rdf functions worksheet that returns the user to the Data Sheet This is minor point though and the spreadsheet was found to be well laid out clear and easy to understand There are a couple of issues that should be considered when preparing the tool for release to organisations external to the Environment Agency The first consideration relates to the applicability of the model External users should be made fully aware of its limitations and of the need to carefully check the accuracy of the model results This is a minor point however a more serious issue relates to the robustness of the dll which has caused the tool to crash The dll should be rigorously debugged before the tool is made freely avai
30. ing to the returning of the single river solution for both rivers from appearing El Microsoft Excel IGARF1v4_Test4 xls laj x E Ble Edt View Insert Format Tools Data Window Help 18 xj DSO SRY SBBS 5 o B b 2a v2 ez o Essee zF oA 2 Ad X Project name rol jame Test4 A ion well Conceptual Model Parameters Abstraction rate Compensation m3id returns m3id Well 1 na if Sel TEF N Conceptual Model FE River aquifer contact length Width Sediment thickness Sediment hydraulic conductivity of well to river Ed h The drawdown at the well is greater than 50 of the Dur effective saturated thickness of the aquifer This Pumping rate for may affect the validity of the solution Upstream limit Downstream li Calculate Now ENVIRONMENT Last calculated at AGENCY Monitoring well location y Last saved at 1 ae ie ADI Data Sheet Evoliion of River Depletion A Profle of Rive Depletion f Tare Drawdoanl Draweown Contours 7 Parodie Astraction a al pram fy G atoshese n a Oglar ERMA Ready Calculate lI INUM i f Figure 25 Test 4 Data Sheet 22 El Microsoft Excel IGARF1v4_Test4 xls S Eile Edit wew Insert Format Tools Data Window Help Jose B S6RY sBOAs o gt zi Alara au e 7 oF Al hd Evolution of River Flow Depletion Evolution of River Flow Depletion Click on the chart to return to the Data Sheet WAR
31. ion well see User reach i Information sheet for further discussion The Depletion Upstream drawdown at the well is greater than 50 of the 100 Downstream li effective saturated thickness of the aquifer This may affect the validity of the solution 5 een i alculate Now ENVIRONMENT Last calculated at AGENCY Monitoring well location y Last saved at 1 ae So Re iad aM MP ok g 4 b bih Data Sheet Evolution of River ion Profile of River ion Time Drawdown Drawdown Contours _ Periodic Abstraction Perioc 4 oew A Atoshpes e n a OR AB O 4 A oO Ready Calculate 1 al NUM if Figure 13 Data Sheet of IGARF model used for ZOOMQ3D comparison 4 12 4km Figure 14 Figure 15 4km Well 9M WO w QOT IAN yUNP IAN JIPON ZOOMQ3D model for comparison 4 Depletion rate m day m Profile of river depletion at time 100 days IGARFI v4 x ZOOM So io f o N a f N 1 S a f S 1 So a fn 0 2000 1500 1000 500 0 500 1000 1500 2000 Distance downstream of well m Profiles of river depletion for ZOOMQ3D comparison 4 13 9M woy WOT JOALI SI YL ATepunog Jopour poy poxty 5 Numerical accuracy of the spreadsheet The IGARF1 v4 spreadsheet can be used to investigate a vast number of different aquifer configurations by varying the position of abstraction boreholes with respect to rivers and no flow boundaries
32. isconnected Warnings easily removed by modifying Scale Factor No warnings errors observed Warnings easily resolved by modifying Scale Factor No warnings errors observed No warnings errors observed No warnings errors observed No warnings errors observed No warnings errors observed but oscillation in profile of river depletion due to low depletion rates after pumping stops See Figure 29 No warnings errors observed No warnings errors observed 25 E3 Microsoft Excel IGARF1 4 no report xls Read Only amp Eile Edit wiew Insert Format Tools Data Window Help DEESA SMBS oce w i aral A16 bd Profile of River Flow Depletion Click on the chart to return to the Data Sheet Profile of river flow depletion at time 110d Chart Properties x axis minimum upstream sem m AE REE 1000 Not Applicable Not Applicable Not used for single river system River 1 downstream m Evaluation time for profile d he parameters used to calculate these data have not been saved in a report le 0 007 Project Name Test 5 Local river flow depletion rate m3 dim esses s55 8388 82a 8 River 1 At 10m 0 002 No Flow boundary At 1000m cael Abstraction Well E Well 1 0 Re eu Name s s s s s s ee ee eee eee e o o ese 8ssf 8 8 amp amp 2 8 8 8 8 Ff 8 BS Calculate Now i Position along reach m ese data have been
33. ive saturated thickness 100 m 7 es m m z m eed m 5 mid pistance of wellto river 5000 m not used m o a q not used m nausea 1 2 z h Pumi Upstream limit o Downstream lin Calculate Now ENVIRONMENT m Last calculated at AGENCY m Last savedat Maa h CT ee F 5 4 4 gt gt i Data Sheet Evolution of River Depletion Profile of River Depletion Time Drawdown Drawdown Contours Periodic Abstraction Perioc 4 oraw Ty G Autoshapes gt a Ready CB4B 4 A 500 Calculate i al Test 3 Data Sheet INuM TT Figure 22 20 El Microsoft Excel IGARF1v4_Test3 xls
34. iver Flow Depletion sheet cccccesccesseeseeeseeeteesteeees 19 Test 3 Data SHEE eo iioo aa Er r A E ER 20 Testa tdi functions sheet ceca scesodun e ae a a E r 21 Test 3 Evolution of River Flow Depletion sheet ccccccessesseeseeseetteeeteeens 21 Test4 Data SHEE nonner tenas asioin a wa eset 22 Test 4 Evolution of River Flow Depletion sheet ccccccsessesseeseeeseeesseeeteeees 23 Test4 rdf functions SHeet soere ueeren ania E TE EEE AS EEEE aS 23 Data Sheet for Test 5 spreadsheet model oo ee ceeceesseessecsseceseeesteeeteesteesseeeseeees 24 Irregular profile of profile of river depletion during use of Test 5 model 26 Data sheet for Test 6 model 22552 eee aw ee on ae 27 Data sheet for Test 7 model icsccsnssteeirisusc tenunishueacereipyein tee imetaevwmabiane Genes 28 TABLES Table 1 Summary of the comparative models cccceeceesseesessseeeseeesscsseceeeceeesesseeeeeeeneeenees 5 Table 2 Summary of Test sensitivity analysis cccccceeseesseesccesseeesseeseceesceeeseneeeeseeeseeens 17 Table 3 Summary of Test 5 model parameters adjustment process and warnings 25 Table 4 Summary of Test 7 model parameters adjustment process and warnings 29 iii Summary This report describes the testing of the IGARF1 v4 spreadsheet tool developed by the Environment Agency for the assessment of the impacts of groundwater abstraction on river flows This spreadsheet constructed in
35. lable Once this has been achieved the development of the spreadsheet should be publicised and disseminated widely to enable other hydrogeologists to test their conceptual understanding of simple groundwater systems readily 31 References ENVIRONMENT AGENCY 2004 IGARF1 v4 User Manual Environment Agency Report NC 00 28 HANTUSH M S 1965 Wells near streams with semi pervious beds Journal of Geophysical Research 70 12 2829 2838 HUNT B 1999 Unsteady stream depletion from groundwater pumping Groundwater 37 1 98 102 JACKSON C R 2001 The development and validation of the object oriented quasi three dimensional regional groundwater model ZOOMQ3D British Geological Survey Internal Report IR 01 144 THEIS C V 1941 The effect of a well on the flow of a nearby stream American Geophysical Union Transactions 22 3 734 738 32
36. le This is observed in the evolution of river depletion rates Figure 12 which illustrates the lower river leakage rates to the aquifer in the numerical model 10 Profile of river depletion at time 200 days 18 5 i IGARFI v4 x ZOOM 14 4 2o 124 10 4 g 8 a E 3 64 E A 44 2 0 2000 1500 1000 500 0 500 1000 1500 2000 Distance downstream of well m Figure 10 Profiles of river depletion for ZOOMQ3D comparison 3 i8 Time drawdown at 125m 0m 12 16 4 14 4 Z 3 i 12 4 S 104 5 g 8 s a z 3 E g a 64 A y a z IGARFI v4 Lo Pa x ZOOM Number of perched ZOOM river nodes 0 T T 1 r T r T T T 0 0 20 40 60 80 100 120 140 160 180 200 Time days Figure 11 Time drawdown curves for ZOOMQ3D comparison 3 River depletion over reach 1000 to 1000 m 10000 r 12 9000 8000 z 7 z 7000 4 A E6000 d a S N so00 S E a 400 3 5 3 amp 30004 z a a 2000 4 5 IGARFI v4 a 1000 4 Sp ZOOM Number of perched ZOOM river nodes 0 r r r r r 0 0 20 40 60 80 100 120 140 160 180 200 Time days Figure 12 Evolution of river depletion curves for ZOOMQ3D comparison 3 11 4 5 COMPARISON 4 In this comparison a numerical model is constructed which represents the example described in Appendix C 4 of the IGARF1 v4 User Manual In this scenario an abstraction borehol
37. lowing step were made to try to produce an acceptable solution l 2 4 Increase the Scale Factor to 20000 Increase the Scale Factor to 30000 This removed the first warning relating to Fourier Transform Output chart falling too rapidly Increase the Power parameter to 2 This caused the first warning relating to Fourier Transform Output chart falling too rapidly to return Increase the Scale Factor to 100000 Though it was possible to stop the first warning to occur it was not possible to stop the tool from presenting the following message which is shown in Figure 18 WARNING The impact of the two river system is not being resolved and the single river solutions for each river are being returned Refer to the Numerical Parameters section on the rdf functions worksheet to determine whether an inappropriate Scale Factor is being used 2 Microsoft Excel IGARF1v4_Test1 xls x File Edit Yiew Insert Format Tools Data Window Help 18 x OSM SRY SBOP O o S f hy P
38. m of the well with time shown on a log scale and e the profile of river depletion along the central 20 km one of the rivers after 200 days of pumping Ei Microsoft Excel IGARF1v4_Z00M1 xls la x G Eile Edit view Insert Format Tools Data Window Help 6 x JOSE SRY SEBS 5 B wl i aria Je e z 0 E2 sale z E 0A 2 A1 X Project name ZOOM comparison 1 7 ction well ana Conceptual Modei Parameters Abstraction rate Compensation im na AP A 5 Transmissivity returns m3 d Sel Le Mey S Storage coefficient Conceptual Model M 3 Effective saturated thickness y Depth E wian River aquifer contact length Width i be N Sediment thickness jo g a E Sediment hydraulic conductivity Distance of well to river T F E wan oo River aquifer contact length Width m T Sediment thickness oim g Z Sediment hydraulic conductivity 1 00E 01 mid S Distance of well to river 2000m
39. ment except in one example where as expected the river becomes perched due to abstraction The use and testing of the spreadsheet has illustrated that in most cases it returns accurate results In general it is straightforward to obtain the correct results however in approximately half of the model runs the Scale Factor and Power parameters on the rdf functions sheet had to be adjusted to resolve the warning messages that are presented after the solution is calculated In most cases the warning messages can be resolved quickly generally by adjusting the Scale Factor parameter only However for some models it was not possible to resolve the warning messages by adjusting either or both of the Scale Factor and Power parameters This problem occurred in examples with realistic parameters and did not just occur in aquifers with unrealistic data sets as expected Whilst numerical warning messages are presented frequently after the calculation of a solution by the IGARF1 v4 spreadsheet the appropriate warnings were always found to appear at the correct time when they were required to direct the user iv l Introduction The Environment Agency s IGARF1 v4 tool is a spreadsheet based modelling application created in Microsoft Excel that enables the investigation of the impact of groundwater abstraction on river flows in a system containing either one or two straight line rivers The tool uses three different analytical solutions to asses
40. ng the reporting facility After having reached the end of Section 5 2 4 of the User Manual the following steps were performed e The contents of the cell containing the Downstream limit of reach evaluated were copied and pasted into the cell above containing the upstream limit e The Upstream limit of reach evaluated was then adjusted to be 1000 instead of 1500 This resulted in the error message below Which could only be corrected by modifying its value in the Data Sheet See Figure 2 e This error message was not presented if values greater than 1500 were then input as the upstream reach limit This may not be viewed as a bug but rather as the problems associated with the use of Copy Paste instead of the use of Copy Paste Special PValues E3 Microsoft Excel IGARF_Otter xls 8 x Fle Edt view Insert Format Tools Data window Help l x joe B 2R sBBS O o A gt I aria 0 B z ul Z E2m S e B O A B7 v 1000 Evolution of River Flow Depletion Click on the chart to return to the Data Sheet a Chart Properties x axis minimum Oo d River depletion over reach 1500 m to 1500 m m3 d x axis maximum 200 d Upstream limit of 3500 reach evaluated m 3000 Downstream limit Ss of reach evaluated m a 2500 The parameters used to calculate c these data have not been saved in amp 2000 la report file 2 a 3 x 5 Fa x The downstream limit must be greater than the u
41. nt thickness 3 Sediment hydraulic conductivity Distance of well to river Depth width River aquifer contact length Width Sediment thickness Sediment hydraulic conductivity Distance of well to river River 1 Hunt p 7 Dur Depletion oars le Pro a Downstream lim ne ra 100d Calculate Now AGENCY T ee ceg A A j ae Ny N ge gt 4 4 gt Data Sheet Evolution of River Depletion Profile of River Depletion Time Drawdown Drawdown Contours Periodic Abstraction Perioc tT Joram By G autoshaesy a OR 4M o 4 A oa Ready Calculate 1 I al INUM Figure 16 Test 1 Data Sheet 14 On calculating the solution it is found that the message box appears warning of numerical accuracy issues The rdf functions sheet is shown in Figure 17 and this shows that the Fourier Series Output curve falls to zero too rapidly To remove these errors the fol
42. oring well location y Last saved at 1 ae ee 40 gt PiN User Information Cone Model Selection Data Iny am Data Sheet Evolution of River Depletion Profile of River Depletion ows Ty G Atosheess Sk OBIA A ERR Ready Calculate 1 Ef INUM Figure 19 Test 2 Data Sheet 18 El Microsoft Excel IGARF1v4_Test2 xls S Eile Edit wew Insert Format Tools Data Window Help JO se BSR steso me w i Alara
43. parison 1 except that the periodic abstraction is included and the time step is modified In this mode there are 11 time steps per month which increase in length from one day at the start of the month A single chart is produced Figure 8 which shows the comparison between the analytical and numerical model for e the evolution of river depletion over the reach 2 km upstream to 2 km downstream of the well El Microsoft Excel IGARF1v4_ZO0M2 xls 18 x 1 File Edit View Insert Format Tools Data Window Help lal x jos O S6RY sBRSlO o gt w i Alara 2 se 7 u Essems 4 e B o A 3 AL z Project name ZOOM comparison 2 r Tai Abstraction well 4 Conceptual Model Parameters Abstraction rate Compensation T na A Sg 5 Transmissivity 1000 m2id m3id returns m3 d Sel M
44. pstream limit Project Name Not Specified River Otter At 25m ea Abstraction Well Not Specified Name 0 0 20 40 6 80 100 120 140 160 180 200 Calculate Now Time d Not used for single river system River Otter data have been calculated using a single river solution The River Otter is a Hunt River 5 ENVIRONMENT ENCY 1414 P Data Sheet Evolution of River Depletion Profile of River Depletion Time Drawdown Drawdown Contours Z Periodic Abstraction Perioc 4 Drow Autcshopes gt a CEs A A RMA Ready Calculate 1 I aa Ce NUM fama Figure 2 Screen dump showing bug 2 3 3 BUG3 The drop down box on the Periodic Abstraction sheet is not protected and can be deleted 4 Comparison with numerical model 4 1 BACKGROUND Four comparisons have been made between the results produced by the IGARF spreadsheet with those produced by the finite difference numerical groundwater flow model ZOOMQ3D Jackson 2001 Except for comparison four the numerical models contain a uniform square mesh spacing that is smaller or comparable to the distances between the simulated abstraction boreholes and rivers Consequently the numerical models are considered to contain sufficient resolution The numerical models used in comparison 1 to 3 are not presented as figures because they use simple uniform dense meshes which are clear to envisage Comparisons are been made be
45. rning remained returning of the single coefficient ten river solution for both rivers times Decrease storage With Power Scale Factor 0 Fourier Series coefficient ten Output chart falls to zero too rapidly times Increase Scale Factor to 5000 removes all warnings Increase saturated Warning remained returning of the single thickness ten river solution for both rivers times Decrease saturated Warning remained returning of the single thickness ten river solution for both rivers times Increase river Warning remained returning of the single depth ten times river solution for both rivers Increase river Warning remained returning of the single width ten times river solution for both rivers Halve distance to 5000 Increase Scale Factor to 20 000 removes rivers warnings Reduce distance to 5000 Increase Scale Factor to 10 000 removes both rivers warnings In general for this aquifer configuration the warning relating to the single river solution being returned for each river remained in most of the cases described in Table 2 and could not be resolved by adjusting the Scale Factor and Power parameters on the rdf functions sheet However no warning messages were presented when the storage coefficient was reduced by a factor of ten or when the distance between the rivers and thus between the rivers and the well was reduced 17 5 33 TEST 2 TWO HANTUSH RIVERS 10KM APART ABSTRACTION BOREHOLE HALF WAY BETWEEN RIVERS Test 2
46. s the impacts in a vide variety of simplified surface groundwater systems The analytical solutions are those presented by l Theis 1941 Analytical solution to calculate the quantity of water supplied from a fully penetrating infinite river or infinite straight line recharge boundary due to a constant rate groundwater abstraction 2 Hantush 1965 Analytical solution to an infinite straight line fully penetrating river considering the influence of low hydraulic conductivity river bank or river bed sediments 3 Hunt 1999 Analytical solution to an infinite straight line partially penetrating river considering the influence of low hydraulic conductivity river bed sediments This work describes the testing that has been undertaken on the latest version version 4 of the IGARF1 Excel spreadsheet The following tasks have been undertaken as part of the five person days of testing and this report is broken down into sections which approximately relate to each of these tasks l Undertake the spreadsheet modelling described in the case study in Section 5 of the IGARF1 v4 User Manual Environment Agency 2004 Try to find bugs in the program by simulating aquifer systems with extreme parameter values Identify aquifer configurations for which the tool has difficulty in producing a correct solution e g steep groundwater head gradients very concentrated diffuse river impacts Compare IGARF results with simple numerical model
47. s to check accuracy considering that IGARF can assess heads at all points in model space and therefore the numerical model may require a very fine mesh Assess how often the numerical accuracy issues arise in cases e Using realistic datasets different to the case study in Section 5 of the User Manual e With extreme parameters in unrealistic situations When numerical issues do occur assess how easy they are to correct Check that the appropriate numerical warning messages are shown at the appropriate times All the spreadsheet modelling referred to in this work has been performed on a Pentium III PC with 512 Mb of RAM running Windows 2000 and Microsoft Excel 2000 2 User Manual case study of the River Otter The case study described in Section 5 of the User Manual for IGARF1 v4 Environment Agency 2004 has been replicated using both versions of the Excel spreadsheet i e IGARF1v4 xls and IGARF1v4 no report xls The no report version is for use on portable lap top machines and does not incorporate the facility to produce short reports or modelling logs which are printed using the Environment Agency s computing network This case study illustrates its application to the assessment of the impact of an abstraction close to the River Otter in Devon flowing across the Permo Triassic sandstone The steps described in the User Manual have been replicated using both versions of the Excel file No differences have been found when
48. sh Geological Survey carries out the geological survey of Great Britain and Northern Ireland the latter as an agency service for the government of Northern Ireland and of the surrounding continental shelf as well as its basic research projects It also undertakes programmes of British technical aid in geology in developing countries as arranged by the Department for International Development and other agencies The British Geological Survey is a component body of the Natural Environment Research Council Keyworth Nottingham NG12 5GG T 0115 936 3241 Fax 0115 936 3488 e mail sales bgs ac uk www bgs ac uk Shop online at www thebgs co uk Murchison House West Mains Road Edinburgh EH9 3LA 0131 667 1000 Fax 0131 668 2683 e mail scotsales bgs ac uk London Information Office at the Natural History Museum Earth Galleries Exhibition Road South Kensington London SW7 2DE T 020 7589 4090 T 020 7942 5344 45 Fax 020 7584 8270 email bgslondon bgs ac uk Forde House Park Five Business Centre Harrier Way Sowton Exeter Devon EX2 7HU T 01392 445271 Fax 01392 445371 Geological Survey of Northern Ireland 20 College Gardens Belfast BT9 6BS T 028 9066 6595 Fax 028 9066 2835 Maclean Building Crowmarsh Gifford Wallingford Oxfordshire OX10 8BB T 01491 838800 Fax 01491 692345 Parent Body Natural Environment Research Council Polaris House North Star Avenue Swindon Wiltshire SN2 1EU 01793 411500 Fax 017
49. t reason for this has not been identified due to time constraints but the difference is not sufficiently significant to draw the conclusion that there are errors in either of the models River depletion over reach 2000 to 2000 m 4000 IGARF1 v4 3500 ZOOM 3000 4 i t Fi 2500 H 2000 4 2 f 1500 oe ae x 1000 4 500 0 i 0 20 40 60 80 100 120 140 Month Figure 8 Evolution of river depletion curves for ZOOMQ3D comparison 2 4 4 COMPARISON 3 In this comparison a model is constructed to illustrate the impact of perching of the rivers on the solution An abstraction borehole is located 125 m from a Hunt type river in an aquifer with a transmissivity of 200 m day and storage coefficient of 5 The full parameter data set is illustrated in Figure 9 which shows the Data Sheet for the IGARF model The numerical model is 20 km square and has a 125 m square mesh The river is 125 m from the pumped well and is assigned the same parameters as those input to the IGARF spreadsheet A one day time step is used to simulate the system Three charts are produced Figures 10 to 12 which show the comparison between the analytical and numerical model for e the time drawdown at an observation well located on the river e the evolution of river depletion over the reach 1 km upstream to 1 km downstream of the well and e the profile of river depletion along the central 4 km of one of
50. te scale factor is being used Chart Properties x axis minimum d x axis maximum 100 d Upstream limit of reach evaluated m Downstream limit of reach evaluated he parameters used to calculate hese data have not been saved in ja report file Project Name Test 1 River 2 River 1 Abstraction Well Well 1 Name Calculate Now At 5000m At 5000m River depletion m3id River depletion over reach 2000 m to 2000 m m3 d 40 50 60 70 Time d River 1 River 2 80 These data have been calculated using a two river solution The River 2 is a Hunt River The River 1 is a Hunt River liad Draw gt Autoshapess gt a Ready Calculate 16 Test 1 Evolution of River Depletion sheet 5 2 SENSITIVITY ANALYSIS USING TEST 1 To examine the influence of some of the model parameters on the occurrence of numerical accuracy warnings a limited sensitivity analysis was performed using the Test model Each of the parameters on the Data Sheet was modified in turn and the effects on the solution observed These changes are outlined in Table 2 Table 2 Summary of Test 1 sensitivity analysis Change made Original New Effect of change Warnings value value persist Reduce 1000 100 Warning remained returning of the single transmissivity ten river solution for both rivers times Increase storage A Wa
51. th Width 20 m Sediment thickness Sediment hydraulic conductivity Distance of well to river Depth Width 20m 2 piver aquifer contact length Depth 100 0 5 rg 3 T 1 00E 01 Distance of well to river 4000 5000 2m 1440 d Feach m Pupin rete 4 Depletion Upstream limit le iam a Downstream li ig pam a Calculate Now ENVIRONMENT m Last calculated at AGENCY Monitoring well location y ai Last saved at 19 05 2004 16 22 E 44 gt b Data Sheet Evolution of River tion Profile of River ion Time Drawdown Drawdown Contours Periodic Abstraction Perioc 4 Joan gt Be amosse SOR 4M O 4 A En Ready Calculate i I NUM ma Figure 31 Data Sheet for Test 7 model The changes to the model parameters and their effects on the solution are listed in Table 4 In all but three of the eleven simulations performed using this model it was the case that either no warnings or errors were observed or when warnings were presented they could easily be resolved by adjusting the Scale Factor and Power parameters However the numerical solution process failed to produce adequate results in three cases one of which represents a realistic system When the transmissivity was reduced to 500 m day two types of warnings were presented which could not be resolved by adjusting the Scale Factor and Power parameters These relate to the rapid fall of the Fourier Series Output for both rivers and to the single ri
52. the dll which contains the analytical solutions The spreadsheet has crashed a number of times less than ten when the Calculate Now button has been pressed In these cases a Windows pop up error message is presented which indicates that there has been a memory access error It is suspected that this is likely to be a problem with the code contained in the dll but it could be an error within an Excel macro 2 copy and pasting values between data entry cells in the spreadsheet This can cause the rules which are associated with the values that are allowed in the cells to be corrupted If this is not considered as a bug it should be recommended that users should use Copy Paste Special PValues 3 the drop down box on the Periodic Abstraction sheet which is not protected and can be deleted Four models have been constructed using both IGARF1 and ZOOMQ3D Jackson 2001 and a comparison has been made between the results of each In all cases the results have been in close agreement except for the model in which the river becomes perched due to the abstraction The analytical solutions do not represent the perching of river As expected drawdowns are greater and river depletion rates lower in the numerical model The use and testing of the spreadsheet has illustrated that in most cases it returns accurate results In general it is straightforward to obtain the correct results however in approximately 50 of model runs the Scale Factor and Pow
53. the rivers after 200 days of pumping El Microsoft Excel IGARF1 4_Z00M3 xIs S Eile Edit wiew Insert Format Tools Data Window Help 18 x le x DEESA s neS oce A ie C2 pal z Arial 10 B z uzam n E n a A 2 ZOOM comparison 3 Abstraction well is ie me jell Sel WAY FE Conceptual Model bd Conceptual Model Parameters 200 m2 d 0 05 100 m 1m 5m 5m 0 1m Abstraction rate Compensation returns m3 d m3id m River 1 Hunt Aquifer Sediment hydraulic conductivity Distance of well to river 1 00E 01 mid 125 m not used m To a p B Distance of well to noflow boundary 11875 10000 0 1 The River 1 has become disconnected affecting the 4 E Dur validity of this solution Consider the signficance of Pumi this with respect to the real river system see User Depletion Upstream limit Information sheet for further discussion The Downs
54. traction Table Z Impact of Pumping Test _f calculations Audit rdf functions rdf functions 2 IKI A ow R amp AutoShapes a CH4B o 4 A Ready Calculate 1 I ET NUM Figure 20 Test 2 rdf functions sheet El Microsoft Excel IGARF1v4_Test2 xls 18 x Eie Edt view Insert Format Tools Data Window Help ale x Deusy see o aA E A ara zno e zu Hy OvA Downstream _limi 100 Evolution of River Flow Depletion Click on the chart to return to the Data Sheet on the rdf functions worksheet to determine whether an inappropriate scale factor is being used WARNING The impact of the two river system is not being resolved and the single river solutions for each river are being returned Refer to the Numerical Parameters section Chart Properties x axis minimum 0 d River depletion over reach 100 m to 100 m m3 d x axis maximum 100 d Upstream limit of reach evaluated m Downstream limit of reach evaluated he parameters used to calculate hese data have not been saved in ja report file River depletion m3id Project Name Test 2 River 2 At 5000m River 1 At 5000m Abstraction Well Well 1 Name T T T T T T T EEEE 0 10 20 30 40 50 60 70 80 90 100 Time d River 1 River 2 These data have been calculated using a two river solution The River 2 is a Hantush River Th
55. tream lim drawdown at the well is greater than 50 of the effective saturated thickness of the aquifer This morenn oo Calculate Now AGENCY T ae EE Ay j FZ ad iala gt gt i Data Sheet Evolution of River Depletion Profile of River Depletion Time Drawdown Drawdown Contours Periodic Abstraction Perioc iT draw gt Ty G Autoshopess gt amp IOR AB O 4 A S EB Ready Calculate Num ay Figure 9 Data Sheet of IGARF model used for ZOOMQ3D comparison 3 The impact of the river becoming perched i e when the groundwater head falls below the bed of the river is clearly visible in all three comparative plots shown in Figures 10 to 12 The numerical model predicts that the river becomes perched over an 875 m length of channel equivalent to seven model river nodes by the end of the 200 day period of abstraction represented by seven central points on curve in Figure 10 However the section of the river closet to the abstraction well becomes perched after only two days of pumping in the numerical model This perching has a significant impact on the subsequent drawdown and depletion rates At early times after the start of pumping the time drawdown curves for the two models are in relatively close agreement However after approximately 25 days of abstraction the curves diverge Rates of drawdown are more rapid in the numerical model because perching of the river limits the supply of water to the well close to the boreho
56. tween IGARF and ZOOMQ3D for the time drawdown curves the evolution or river depletion curves and the profiles of river depletion for models using both constant and periodic abstraction rates Table 1 gives a summary of the models described in the following four sections Table 1 Summary of the comparative models Comparison Description 1 Pumped well equidistant from two Hunt type rivers that are 4 km apart Hydraulic parameters are broadly representative of a Chalk aquifer i e a transmissivity of 1000 m day and storage coefficient of 1 Abstraction borehole pumps at a constant rate of 10 000 m day for 200 days Comparative plots are produced for the time drawdown at an observation borehole for the evolution of river depletion and for the profile of river depletion The model is the same as that constructed in Comparison 1 except it includes periodic abstraction The well pumps for half of each year between May and October at a rate of 10 000 m day A comparative plot is produced for the evolution of river depletion over time A model is constructed to illustrate the impact of river becoming perched on the model solution An abstraction borehole is located 125 m from a Hunt type river in an aquifer with a transmissivity of 200 m day and storage coefficient of 5 Comparative plots are produced for the time drawdown at an observation borehole for the evolution of river depletion and for the profile of river depletion
57. ution for infinite reach Analytical Solution for Steady State flows over an infinite reach 27 River 1 0 1888 River 1 0 5000 River 1 0 5000 28 River 2 0 1888 River 2 0 5000 River 2 0 5000 0 3776 Total 4 0000 Total 14 0000 z ld 4 gt gt I Periodic Abstraction Periodic Abstraction Table Z Impact of Pumping Test calculations Audit rdf functions rdf functions 2 tal IT ow amp AutoShapes a CH4B 4 A Ready Calculate 1 I ET NUM Figure 23 Test 3 rdf functions sheet El Microsoft Excel IGARF1 4_Test3 xls Eile Edit View Insert Format Tools Data Window Help jDeel6RY smad o o e zrlm 2 AL hd Evolution of River Flow Depletion Arial z4 e z T Evolution of River Flow Depletion Click on the chart to return to the Data Sheet WARNING The impact of the two river system is not being resolved and the single river solutions for each river are being returned Refer to the Numerical Parameters section on the rdf functions worksheet to determine whether an inappropriate scale factor is being used Chart Properties x axis minimum 0 d River depletion over reach 2000 m to 2000 m m3 d x axis maximum 100 d Upstream limit of reach evaluated m Downstream limit of reach evaluated 1000 he parameters used to calculate hese data have not been saved in ja report file 800 600 400 River depletion
58. ved Two types of warnings are presented which could not be resolved by adjusting the Scale Factor and Power parameters These relate to the rapid fall of the Fourier Series Output for both rivers and to the single river solution being returned for each river for the evolution of river depletion Warning presented The impact of the two river system is not being resolved and the single river solutions for each river are being returned Failed not stop warning by adjusting Scale Factor and Power No warnings errors observed No warnings errors observed 29 6 Conclusions The IAGRF1 v4 spreadsheet tool has been found to be a Powerful and easy to use application that generally produces accurate results rapidly However during the testing process problems have been encountered some of which could be considered serious The testing process has been broken down into a number of tasks the first of which was to replicate the use of the spreadsheet as it is described in Section 5 of the IGARF1 v4 User Manual i e to reproduce the River Otter case study This has been done using both versions of the Excel spreadsheet IGARF1v4 xls and IGARF1v4 no report xls and no differences have been observed between the modelled results and those presented in the User Manual Three bugs have been encountered which relate to coding issues or to features of the spreadsheet These relate to 1 what appears to be problems associated with
59. ver solution being returned for each river for the evolution of river depletion These warnings were also presented and could not be resolved by adjusted the Scale Factor and Power parameters when the river bed conductivity was reduced to below 10 mday 28 Table 4 Original parameter set shown in Figure 31 Difference from original parameter data set Transmissivity increased to 4000 m day Transmissivity decreased to 500 m day Storage coefficient reduced to 0 01 Storage coefficient reduced to 0 001 Storage coefficient increased to 0 25 Saturated aquifer thickness and depth of Hantush type river reduced to 10 m Sediment hydraulic conductivity of Hantush type river reduced to 10 Sediment hydraulic conductivity of both rivers reduced to 10 Abstraction increased to 10 000 miday Abstraction reduced to 100 m day Summary of Test 7 model parameters adjustment process and warnings Warning produced relating to too rapid fall of Fourier Series Output Easily corrected by increasing Scale Factor to 20000 Results Warnings persist No warnings errors observed Warning presented The impact of the two river system is not being resolved and the single river solutions for each river are being returned Failed not stop warning by adjusting Scale Factor and Power No warnings errors observed No warnings errors observed No warnings errors observed No warnings errors obser

Testing of the IGARF1 v4 spreadsheet tool for assessing the impacts

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