ARS | Publication request: RUNOFF MAPPING USING WEPP EROSION MODEL AND GIS TOOLS

Submitted to: Computers and Geosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 22, 2005
Publication Date: October 1, 2005
Repository URL: http://hdl.handle.net/10113/14165
Citation: De Jong Van Lier, Q., Sparovek, G., Flanagan, D.C., Bloem, E., Schnug, E. 2005. Runoff mapping using WEPP erosion model and GIS tools. Computers and Geosciences. 31(2005):1270-1276.

Interpretive Summary: When rain falling exceeds the capacity of the soil to absorb it, runoff occurs. It is difficult and expensive to measure runoff from fields and watersheds, due to costs of equipment and labor. However, the amount of water that can or may runoff from a particular site can be very important in terms of the amount of soil erosion that can occur, or the loss of nutrients or pesticides. In this study we used a computer simulation model (WEPP) to estimate the amount of runoff at many points within a watershed. We also used special mapping tools and geographic information systems to be able to see in a watershed how runoff is distributed. The results show that the predicted runoff is largely affected by the climate, geology and agricultural management at a location. This research and the mapping tools developed impact scientists, hydrologists, engineers, land managers and others dealing with assessment of watershed runoff and soil loss, and possible land management strategies to reduce them. Better knowledge of critical locations of potential high runoff can allow for more targeted application of control practices.

Technical Abstract: Soil erosion, associated with environmental impacts and crop productivity loss, is usually considered the most impacting of surface hydrology processes. Runoff plays a major role in the erosion process, but also has a significant importance by itself as it directly influences several surface hydrology processes. In this paper a computer interface (Erosion Database Interface, EDI) is applied which allows processing the surface hydrology output of the WEPP (Water Erosion Prediction Project) erosion prediction model, resulting in a georeferenced estimation of runoff. The application of results is illustrated. WEPP output originally contains non-georeferenced daily information about calculated runoff at the lower end of each Overland Flow Element. EDI, when applied to WEPP result files, allows extracting calculated runoff values, transforming these into annual means and consider them in a georeferenced database readable by a Geographic Information System (GIS). EDI was applied to a 1,990 ha agricultural watershed in southeast Brazil, where predominating land use is sugarcane, forest and pasture. A 100-year climate simulation was used to run WEPP, erosion values were calculated at an irregular resolution of 6 points per hectare and subsequently interpolated for regular raster gridpoints. EDI was applied successfully to prepare an input database for automated calculation of erosion and hydrologic parameters with WEPP and to assign georeferences to mean annual accumulated runoff data in order to be imported into the GIS as a vector database. Resulting maps illustrate that runoff is an integrator of climatic, geologic and agricultural management factors.