2. Useful Tools for Predicting Erosion from Disturbed Rangelands: Disturbed WEPP for Rangelands The Water Erosion Prediction Project in the Forest Service

3. Objectives of Presentation n To present three interfaces for Predicting Water Erosion on Rangelands

4. WEPP... n

5. n n Models soil erosion processes

6. WEPP... n n Models soil erosion processes n Was developed cooperatively with –ARS –NRCS (SCS) –BLM –Forest Service –....

7. WEPP... n Is intended to replace the USLE –Which predicts Erosion Only

8. WEPP... n Is intended to replace the USLE –Which predicts Erosion Only n WEPP Predicts –Runoff –Erosion Rates –Sediment yield

9. WEPP Versions n Hillslope –Describes a single strip of hillslope

10. WEPP Versions n Hillslope –Describes a single strip of hillslope n Watershed –Links hillslopes, channels, and impoundments –Very difficult to run

11. WEPP Versions n Hillslope –Describes a single strip of hillslope n Watershed –Links hillslopes, channels, and impoundments –Very difficult to run n GIS Tool –GeoWEPP Prototype now available –Some enthusiasts are developing custom methods

12. n Hillslope –Describes a single strip of hillslope n Watershed –Links hillslopes, channels, and impoundments –Very difficult to run n GIS Tool –GeoWEPP Prototype now available –Some enthusiasts are developing custom methods n FS WEPP Interfaces –For ease of use on the internet –ARS has one too WEPP Versions

13. WEPP Processes 1 n Rainfall, infiltration, runoff, soil water

14. WEPP Processes 2 n Rainfall, infiltration, runoff, soil water n Soil detachment, transport, deposition and delivery

15. WEPP Processes 3 n Rainfall, infiltration, runoff, soil water n Soil detachment, transport, deposition and delivery n Plant growth, evapotranspiration, and senescence

16. WEPP Processes 4 n Rainfall, infiltration, runoff, soil water n Soil detachment, transport, deposition and delivery n Plant growth, evapotranspiration, and senescence n Residue accumulation and decay

17. WEPP Processes 5 n Rainfall, infiltration, runoff, soil water n Soil detachment, transport, deposition and delivery n Plant growth, evapotranspiration, and senescence n Residue accumulation and decay n Soil consolidation

18. Erosion Processes 1 n Interrill Erosion –Raindrop splash –Shallow Overland Flow

19. Erosion Processes 2 n Interrill Erosion –Raindrop splash –Shallow Overland Flow n Rill Erosion –Concentrated Channel Flow –Assumes about 1 m spacing between rills »Varied for roads

20. Erosion Processes 3 n Interrill Erosion –Raindrop splash –Shallow Overland Flow n Rill Erosion –Concentrated Channel Flow –Assumes about 1 m spacing between rills »Varied for roads n WEPP does NOT model gullying or landslides

21. Overland Flow Elements n Describe variation in soil and vegetation down a hillslope OFE 1 OFE 2 OFE 3

22. FSWEPP File Structure Model WEPP Interface FSWEPP Internet Climate CLIGEN & Prism User Web Browser

23. GeoWEPP File Structure Model WEPP DATA DEM Digital Raster Interface GeoWEPP Topographic Analysis TOPAZ GIS ArcView Climate CLIGEN (& Prism)

24. Limitations to WEPP n Scale may be too small –Users frequently want 10 sq mi + watersheds

25. Example WEPP Application n Fort Carson, Colorado n Nearest Climate Station: Timpas, CO n Typical Slope Length: 300 m (1000 ft) n Steepness: 25% n Soil: Loam n Vegetation: Grass/Sage, about 30% cover n Observed erosion rates: 2.5 Mg/ha (1 t/acre)

26. Disturbed WEPP Performance Avg Erosion = 2.5 Mg/ha

27. Disturbed WEPP Template OFE 1OFE 2 Slope 1 Slope 2 Slope 3 Slope 4 Treatment 1 Treatment 2

28. ERMiT Template OFE 1 OFE 2 Top Slope Average Slope Toe Slope OFE 3 P(Erosion) = f(P(Climate), P(Soil), P(Distribution)) For forest, chaparral, and rangeland fire applications Post processing for mitigation evaluation

29. GeoWEPP Template n Download (or obtain) a digital elevation model … n Select watershed outlet … –Up to 2 sq mi for watershed output (“Offsite”) –No area limit for hillside output (“Onsite”) n Select files developed in WEPP Windows n Do not try ArcView Functions until all GeoWEPP runs complete

30. Download GeoWEPP Topo Data Digital Elevation ModelDigital Raster Graphic From an NRCS Lighthouse Web Site

31. GeoWEPP defines channels and hillslopes Stream Network Using ARS TOPAZ Topographic Model Representative Hillslopes Area = 324 ha (800 acres)

32. GeoWEPP Calculates Hillside Erosion and Sediment Yield Hillside Erosion Using WEPP Watershed Version Sediment Yields from Hills

33. GeoWEPP Calculates Channel Sediment Routing ChannelInput Mg Output Mg 291171 34551 41618 Delivery Ratio0.6 Avg Erosion0.5 t/ha(0.2 t/a) 4 3 2

34. Conclusions n WEPP Technology shows considerable promise for natural resources to aid in site- specific and small watershed erosion analysis on rangelands

35. Questions & Comments?