Applying the SWAT model to a Managed Irrigated Watershed in a Semi-Arid Region: Model Construction

Transcription

1 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

2 Irrigated System N and P Transport Irrigation Water N, P Water Table

3 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.

4 Study Area (Irrigation Patterns) Upstream study region Lower Arkansas River Valley - Study area: 500 km 2 - Irrigation: Canals (earthen) - Irrigation: Groundwater Pumping - Canal seepage

5 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

6 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

7 HRU to Cultivated Fields For all cultivated Fields (3326) Original HRUs - Single land use type - Unique soil type - Single slope Cultivated Field HRUs. (56)

8 HRU Definition Single land use type: - NASS data - Modified later in.mgt files

9 HRU Definition Unique soil type: - STASGO data

10 HRU Definition HRUs: HRUs (5% land use threshold) CF_HRUs Cultivated Field

11 Modify.mgt files

12 Modify.mgt files

13 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

14 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/ /1/ /1/ /1/ /1/ /1/ /1/ /1/ /1/ /1/ /1/ /1/ /1/ /1/ /1/ /1/ /1/ /1/

15 Modify.mgt files

16 Results 1.40E E E+02 Rocky Ford (Arkansas River) Simulated Flow Observed Flow Flow (m 3 /s) 8.00E E E E E

17 Observed vs simulated streamflow

18 Results Over-estimating Under-estimating

19 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

20 Acknowledgements