Applying the SWAT model to a Managed Irrigated Watershed in a Semi-Arid Region: Model Construction Xiaolu Wei Ryan T. Bailey Ali Tasdighi Mazdak Arabi
Irrigated System N and P Transport Irrigation Water N, P Water Table
Motivation Improve SWAT performance in intensive, highly-managed irrigation systems - Designating each cultivated field as a hydrologic response unit (HRU), so that irrigation can be applied according to water rights - Relating the total applied irrigation water to the volume diverted from the river, also according to water rights - Accounting for seepage from earthen irrigation canals to the underlying aquifer - Including nitrate concentration in irrigation water as a source of nitrogen to the soil profile.
Study Area (Irrigation Patterns) Upstream study region Lower Arkansas River Valley - Study area: 500 km 2 - Irrigation: Canals (earthen) - Irrigation: Groundwater Pumping - Canal seepage
Setup the SWAT model for the study area Modify each cultivated field to be a hydrologic response unit (HRU) Modify the.mgt files to provide seasonal planting, irrigation, harvest, and plowing to each of the field (HRU) Results Future work Outline
GIS Environment Input Data Processing and Display Watershed Delineation SWAT Databases Hydrography Land Use HRU Definition Parameterization Editing.mgt files Run SWAT MODEL Output maps Soils x y Weather Stations DDS Calibration (Dynamically Dimensioned Search Algorithms) Weather Stations and Time Series ArcGIS ArcSWAT
HRU to Cultivated Fields For all cultivated Fields (3326) Original HRUs - Single land use type - Unique soil type - Single slope Cultivated Field HRUs. (56)
HRU Definition Single land use type: - NASS data - Modified later in.mgt files
HRU Definition Unique soil type: - STASGO data
HRU Definition HRUs: - 5330 HRUs (5% land use threshold) - 4275 CF_HRUs - 3326 Cultivated Field
Modify.mgt files
Modify.mgt files
Modify.mgt files - Planting/beginning of growing season, crop rotating [1] - Irrigation operation [2] - Harvest operation [5] - Tillage operation [6]: Disk Plow Planting Heat Unit: total heat units for plant maturity HHHH = TT aaaa TT bbbbbbbb when TT aaaa > TT bbbbbbbb mm PPPPPP = HHHH dd=1 Crop Type Planting Day Harvest Day Tillage Day Units - - - Alfalfa 30-Apr 30-Sep 20-Oct Bean 20-May 30-Sep 20-Oct Corn 1-May 25-Oct 14-Nov Melon 15-May 10-Aug 30-Aug Onion 20-Mar 15-Sep 5-Oct Pasture 30-Aug 30-Sep 20-Oct Pumpkin 1-Jun 30-Sep 20-Oct Sorghum 20-May 15-Oct 4-Nov Spring Grain 1-Apr 15-Jul 4-Aug Squash 20-May 25-Jul 14-Aug Sunflower 1-Jun 10-Oct 30-Oct Vegetable 25-Apr 30-Aug 19-Sep Winter Wheat 30-Sep 5-Jul 25-Jul
Modify.mgt files - Planting/beginning of growing season [1] - Irrigation operation [2] - Harvest operation [5] - Tillage operation [6] MGT_OP: 2 IRR_SC: 1 divert water from reach 3 divert water from shallow aquifer IRR_NO: reach/subbasin IRR_AMT: mm Date FieldID Area (m2) Rainfall (m) SurfWater (m) PumpWater (m) 4/1/1999 1098 143235.473 0.013 0 0.009 4/1/1999 2083 31223.626 0.013 0 0.002 4/1/1999 3116 148320.272 0.013 0 0.002 4/1/1999 3076 9341.440 0.013 0 0.012 4/1/1999 3707 420183.008 0.013 0 0.003 4/1/1999 3713 102005.479 0.013 0 0.126 4/1/1999 3705 62775.957 0.013 0 0.048 4/1/1999 3706 972101.375 0.013 0 0.004 4/1/1999 3714 70875.227 0.013 0 0.053 4/1/1999 1113 83599.240 0.013 0.063 0 4/1/1999 3456 58468.600 0.012 0.076 0 4/1/1999 3580 135559.928 0.011 0.079 0 4/1/1999 3670 81341.549 0.012 0.167 0 4/1/1999 1151 5900.879 0.012 0.073 0 4/1/1999 1150 81905.269 0.012 0.162 0 4/1/1999 1076 47180.328 0.013 0.423 0 4/1/1999 2178 165435.683 0.012 0.084 0 4/1/1999 3400 36664.159 0.012 0.035 0
Modify.mgt files
Results 1.40E+02 1.20E+02 1.00E+02 Rocky Ford (Arkansas River) Simulated Flow Observed Flow Flow (m 3 /s) 8.00E+01 6.00E+01 4.00E+01 2.00E+01 0.00E+00 199901 199909 200005 200101 200109 200205 200301 200309 200405 200501 200509 200605 200701 200709
Observed vs simulated streamflow
Results Over-estimating Under-estimating
Future Work - Canal Seepage - Simulate N, P loadings in tributaries and Arkansas River - Enhance simulation of sub-surface flow and reactive transport processes dynamically dimensioned search algorithms - dynamically dimensioned search algorithms
Acknowledgements