Impacts of Input Datasets on SWAT Model Performance and Watershed Hydrology

2015 SWAT Conference at Purdue University, Oct 14-16, 2015

Aleksey Sheshukov and Jungang Gao

Biological & Agricultural Engineering Kansas State University

NSF Grant No. 1313815 SWAT Input Datasets

• Elevation/DEM • LiDAR, 10m, 30m or 100m • Landuse/Land Cover • NLCD, NASS CDL, or Custom CLU-based • Soil • STATSGO or SSURGO • Weather • Point land-based (NCDC) or gridded (NEXRAD, PRISM) • Operation management/Crop rotations

2 Objectives

• Climate dataset: • Assess the variability of three climate datasets (NCDC, NEXRAD, PRISM) in a watershed in West-central Kansas • Evaluate the impacts of climate data on SWAT performance and watershed hydrology

• LULC dataset: • Develop and test a sub-CLU LULC dataset • Identify dominant crop rotation patterns • Evaluate SWAT performance

3 Middle Smoky Hill River (SHRW) Watershed

• 6,310 km2 (1.5 mln acres) • Cedar Bluff Reservoir (West) and Kanopolis Reservoir (East) • Cropland (47%; winter wheat, sorghum and corn) and pasture (47%) • Precipitation variability (380 mm in the west to 630 mm in the east) • 450 m elevation increase (from 440 m to >900 m) 4 Climate Datasets

(NCDC) NOAA National Climatic Data Center

(NEXRAD) Next Generation Weather Radar

(PRISM) Parameter–elevation Regressions on Independent Slopes Model by Climate Group @ Oregon State Univ.

5 • Network of point land-based stations • ~ 1 gauge per 800 km2 • HDMY • >100 years 6 Next Generation Weather Radar WSR-88D (NEXRAD)

• First deployed in 1988 • 160 Radars with: • Spatial Resolution 1x1, 2x2, 4x4 km2 • Temporal Resolution of 6-10 minutes • Stages 1, 2, 3, 4 or MPE Stage III/IV NEXRAD data processing • Compressed and multi-tarred binary file • Hydrologic Rainfall Analysis Project (HRAP) • 8,640 files of hourly data per year (24 x 365 = 8,640 files/yr) • Perl/C/Python scripting for automatic downloading/processing

Monthly.tar 1 Daily.tar 2 Hourly.z 3 Hourly ASCII

Unzip Unzip 1 30 Unzip 30 x 24=720 720 720

• Workflow of converting Stage IV for watershed modeling

Reprojection Define Projection GIS (grid) (720) (720) (720) PRISM climate dataset

• Developed by Climate Group @ Oregon State Univ. • Simulated and calibrated on observed data • Produces short- and long-term climate patterns • Spatial resolution: 4x4 km2 • Temporal resolution: DMY >100 years Climate data for SHRW

푛

푃푐푝푘 = 푃푖 × (푎푖/ 푎푖) 푖=0 (NCDC) 18 temp and 11 precip sites (NEXRAD) 425 grid-cells, 5 radars (PRISM) 425 grid cells

10 NEXRAD / PRISM vs NCDC

Ellsworth, KS:

• PRISM showed superior statistics than NEXRAD • PRISM temperature showed better fit than precipitation • Statistics worsens from East to West

11 NEXRAD / PRISM vs NCDC

PRISM • 11 NCDC stations • PBIAS increased from East to West • PRISM had NEXRAD better stats • NEXRAD fair radar coverage in SHRW

12 NEXRAD Coverage

Legend nm NEXRAD station * Rain gauge station Contour line Best Radar Coverage Better Radar Coverage Fair Radar Coverage Maximum Rader Coverage NEXRAD pBias (%)

< -15 1 - 3 -15 - -7 3 - 5 -7 - -5 5 - 7 -5 - -3 7 - 15 -3 - -1 >15 -1 - 1

13 Crop coverage in the US

Wheat Sorghum

Corn Soybean

14 LULC Datasets

NASS CDL KSLULC • 10-years: 2003-2012 • Developed for Kansas • NASS CDL as basemap • 1,381,719 CLU polygons • 3,993,986 MODIS NDVI pixels • FSA irrigated crop data • Refined field boundaries used for creation of grower and field level databases • Each “field” includes a series of annual crops

15 Crop rotations • Three 3-year crop rotation periods 2006-2008 2008-2010 2010-2012 • 20 dominant 3-year rotations cover 80% of cropland area

16 SWAT model for SHRW

Hays Ellsworth

• 10-m DEM, sub-field LULC, STATSGO soil, 16 crop rotations • 54 subbasins and 7,179 HRUs • Calibrated at 2 sites (Hays, Ellsworth) from 2003-2012

17 SWAT model calibration • NCDC Coverage

• Calibrated with three weather sets

Daily Monthly Yearly NCDC PRISM NEXRAD NCDC PRISM NEXRAD NCDC PRISM NEXRAD NSE 0.42 0.61 -0.15 0.64 0.78 0.74 0.85 0.82 0.78 pBias (%) -4.00 10.36 -5.63 -3.70 10.75 -5.44 -3.99 10.36 -5.60 RSR 0.76 0.62 1.07 0.60 0.47 0.51 0.39 0.42 0.47

18 Annual water budget Monthly water budget

Hays (USC 00143527) NCDC NEXRAD PRISM Precipitation 590 684.9 564.8 Runoff 27 46 20 ET 530 587.8 514.3 Baseflow 6.6 8.7 6.5

Ellsworth (USC 00142459) NCDC NEXRAD PRISM Precipitation 626 856.9 667.4 Runoff 209 367.1 244.4 ET 277 271 263 Baseflow 74.6 133.4 85.9

Hays, KS Ellsworth, KS 19 Crop rotations

Rotations Rotations • The number of rotations ranged from 0 to 20 (some were shifted) • Model performance improved as the number of rotations increased • Third rotation (Winter wheat -> Grain sorghum -> Fallow) showed significant improvement for streamflow

20 SWAT model performance

Base rotation: 2006-2008 2008-2010 2010-2012

2006- 2008- 2010- 2006- 2008- 2010- 2006- 2008- 2010- 2008 2010 2012 2008 2010 2012 2008 2010 2012

21 Conclusions

• Climate dataset: • Three climate datasets (NCDC, NEXRAD, PRISM) showed variability in precipitation data for SHRW with NEXRAD highly overestimating precipitation • Modeled hydrologic budget components were affected by the differences in precipitation for historical and future climate projections • LULC dataset: • Crop rotations improved model performance • SWAT model performance dipped outside of sample period • In general, various input datasets can profoundly impact model results for present and future climatic conditions, and their selection should be based on careful considerations of accuracy and temporal and spatial coverage

22 Thank You!

• Aleksey Sheshukov • [email protected]

• Acknowledgements • Watershed stakeholders at SHRW • NSF:CNH Systems Program, Grant No. 1313815