Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2010
Publication Date: 8/31/2010
Publication URL: http://hdl.handle.net/10113/48577
Citation: Mao, D., Cherkauer, K.A., Flanagan, D.C. 2010. Development of a coupled soil erosion and large-scale hydrology modeling system. Water Resources Research. 46:W08543. DOI:10.1029/2009WR008268. Interpretive Summary: Soil erosion is a serious problem across the U.S. and the world. In order to estimate and effectively manage the land to minimize erosion problems, computer simulation models are often created to represent mathematically the physical processes that occur in nature and cause or impact erosion. In this study, a large scale hydrology model called the Variable Infiltration Capacity (VIC) model was used to estimate processes such as water infiltration into the soil and surface runoff water moving off the soil, and then was linked with a hillslope erosion model using components from WEPP (Water Erosion Prediction Project) to estimate soil detachment, sediment transport, sediment deposition and delivery. Several innovative techniques were used to take information from the VIC model and scale it down to the much smaller size needed for soil erosion predictions. When testing the combined VIC and WEPP code, we found that the soil erosion predictions were very comparable to those from the full WEPP model. Thus assuming that WEPP adequately predicts soil erosion, the linked VIC-WEPP model should also satisfactorily predict soil loss. This research impacts other scientists working with models at large river basin scales, and provides a method for them to estimate soil erosion, which has typically not been done with these models and at these scales in the past.
Technical Abstract: Soil erosion models are usually limited in their application to the field-scale; however, the management of land resources requires information at the regional scale. Large-scale physically-based land surface schemes (LSS) provide estimates of regional scale hydrologic processes that contribute to erosion. If scaling issues are adequately addressed, coupling an LSS to a physically-based erosion model can provide a tool to study the regional impact of soil erosion. A coupling scheme was developed using the Variable Infiltration Capacity (VIC) model to produce hydrologic inputs for the stand-alone Water Erosion Prediction Project - Hillslope Erosion program (WEPP-HE) accounting for both temporal and spatial scaling issues. Precipitation events were disaggregated from daily to hourly and used with the VIC model to generate hydrologic fluxes. Slope profiles were downscaled from 30 arc-second to 30 m hillslopes. Additionally, soil texture and erodibilities were adjusted with simplified assumptions based on the full WEPP model. Soil erosion at the large-scale was represented on a VIC model grid cell basis by applying WEPP-HE to subsamples of 30 m hillslopes. On an average annual basis, results showed that the coupled model was comparable with full WEPP model predictions. On an event basis, the coupled model system captured more small erosion events, with erodibility adjustments of the same magnitude as from the full WEPP model simulations. Differences in results can be attributed to discrepancies in hydrologic data calculations and simplified assumptions in vegetation and soil erodibility. Overall, the coupled model demonstrated the feasibility of erosion prediction for large river basins.