|Ascough Ii, James|
Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2008
Publication Date: 1/14/2009
Citation: Heathman, G.C., Larose, M., Ascough II, J.C. 2009. SWAT Evaluation of Soil and Land Use GIS Data Sets on Simulated Stream Flow. Journal of Soil and Water Conservation. 64(1):17-32. Interpretive Summary: There are several issues to consider in compiling primary input GIS data sets for use in watershed scale hydrologic modeling. This is especially true when using the model as an environmental assessment tool or as a decision-support system for water resource management. The objective of this study was to determine to what extent, the use of various combinations of soil and land cover GIS input data layers affected non-calibrated stream flow estimates, in a large scale agricultural watershed. Based on our results, the SWAT model shows the most variation in stream flow estimates and sediment yield using different land cover data sets. Although the model is sensitive to soil properties, the scale and extent of soil information did not have a substantial impact on model results. In determining the effects of farm conservation practices on diverse watersheds across the U.S., a major objective of the USDA Conservation Effects Assessment Project (CEAP), it is important that our modeling efforts maintain as much consistency as possible in the use of geospatial data sets.
Technical Abstract: The integration of geographical information systems (GIS) and hydrologic models provides the user the ability to simulate watershed scale processes within a spatially digitized computer based environment. Soil type and land cover data are essential GIS data layers used in a wide array of government and private sector activities, including inventory, management, monitoring, and modeling. This investigation was conducted to evaluate the use of SSURGO and STATSGO soil classification systems and the National Agricultural Statistics Survey (NASS) and Gap Analysis Project (GAP) land cover geographic data sets in the watershed scale model referred to as the Soil and Water Assessment Tool (SWAT). Performance of the model was tested on the Cedar Creek Watershed in northeastern Indiana, one of twelve benchmark watersheds in the U.S. Department of Agriculture, Agricultural Research Service (USDA ARS) Conservation Effects Assessment Project (CEAP). Model performance of the annual and monthly stream flow response in SWAT was assessed using the Root Mean Square Error (RMSE), coefficient of determination (R2), and the Nash-Suttcliffe Efficiency coefficient (ENS). Results of this study indicate that there is little influence due to differences in GIS soil input data layers on stream flow estimates and that the use of different land cover layers has a greater effect.