Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 6/29/2008
Publication Date: 6/29/2008
Citation: Baffaut, C., Benson, V.W. 2008. Possibilities and Challenges for Modeling Flow and Pollutant Transport in a Karst Watershed with SWAT. In: Proceedings of the American Society of Agricultural Biological Engineers Annual International Meeting, Providence, Rhode Island, June 29-July 2. Paper No. 083933. Interpretive Summary: The Soil and Water Assessment Tool, a computer simulation tool that predicts flow and pollutant loadings in watersheds, was applied to the James River Basin, in South Missouri. The objective was to evaluate the ability of this tool to simulate flow and pollutant loadings in a region with karst topography and to determine needed improvements. Karst terrain is characterized by springs, sinkholes, and losing streams that provide direct conduits from the soil surface to groundwater and increase the risk of groundwater contamination. Activities such as agriculture, tourism, and residential development accentuate the contamination potentials. Flows were well simulated in the main river reaches. Flow simulation in the upper reaches needs improvement. The frequency of pollutant concentrations and loadings were well simulated. The results of this study are important to scientists and managers of water resources in karst areas in that it gives guidance on how this tool can be used, what its limitations are and what improvements are needed.
Technical Abstract: Karst hydrology is characterized by multiple springs, sinkholes, and losing streams resulting from acidic water percolating through limestone. These features provide direct connections between surface water and groundwater and increase the risk of groundwater, spring and stream contamination. Anthropogenic activities (agriculture, tourism, urban and residential areas) accentuate the contamination potentials. The Soil and Water Assessment Tool (version 2005) was calibrated for the James River Basin, a large watershed (3,600 km2) in Southwest Missouri, to evaluate its ability to simulate flow and pollutant transport in karst areas. Losing streams were simulated by specifying high soil conductivities in the channels. The model was modified to allow infiltrations from sinkholes and losing streams to return to surface waters. The model was calibrated for flow, phosphorus and bacteria using data from four weather stations, five USGS flow gauges and four USGS water quality stations. Results indicated that flow calibration is satisfactory in the main stream reaches but needs to be improved in the upper reaches. Pollutant calibration was acceptable on a frequency basis only. Understanding the assumptions and the limitations is necessary to determine the future development needs of the SWAT model in this domain and to interpret the results obtained with the current version.