Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: June 1, 2006
Publication Date: July 1, 2006
Citation: Bosch, D.D., Flanagan, D.C., Davis, F.M. 2006. Soil Water Modeling in South Georgia Using Wepp Hydrology. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE). July 9-12, 2006, Portland, OR. Paper #062227. Interpretive Summary: The utility of natural resource models, models which predict what is occurring in the environment, is expanding rapidly to meet the needs of society. One application of these models is to look at the probability of flooding, drought, and plant production. A necessary requirement for these predictions is an accurate prediction of the amount of water in the soil. This study examines the application of a highly regarded hillslope model, WEPP, for simulating soil water conditions at a South Georgia, USA, field site. Three years of data were used to fit the model, while four years were used to compare the accuracy of the results. The model simulations of surface runoff were within 30% of the observed annual runoff for the years used for calibration but varied considerably for the years used for model validation. While results indicate that the model will be useful to examine long-term and seasonal patterns, additional work will be necessary to improve the accuracy of the simulations.
Technical Abstract: Soil water is a fundamental component of any field or watershed scale water balance. A basin scale soil water model is being assembled using the runoff and water redistribution functions within the WEPP model. The model uses the runoff, infiltration, plant uptake, and water redistribution functions within WEPP to make predictions of soil water within the vadose zone. The WEPP model was evaluated using runoff and soil water data collected from South Georgia experimental plots where the effects of conservation tillage were examined. WEPP model simulations of surface runoff from the plots were within 30% of the observed annual runoff for the years used for calibration but varied considerably for the years used for model validation. In general, results were better for the simulations of the strip tillage system than for the conservation tillage system. Simulations of soil water in the upper profile were useful for examining seasonal patterns and for examining differences between the two tillage systems.