Submitted to: Transactions of the ASABE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/20/2009
Publication Date: 4/1/2009
Citation: Baffaut, C., Benson, V.W. 2009. Modeling Flow and Pollutant Transport in a Karst Watershed with SWAT. Transactions of the ASABE. 52(2):469-479. Interpretive Summary: The Soil and Water Assessment Tool, a computer simulation tool that predicts flow and pollutant loadings in watersheds, was modified to better simulate water movement from sinkholes and losing streams in karst systems. 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. The model was applied to the James River Basin, in South Missouri. Flow simulation was improved by the proposed changes in the upper reaches where it was most needed. 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, springs and stream contamination. Anthropogenic activities (agriculture, tourism, urban and residential areas) accentuate the contamination potentials. The objectives of this paper are to present a modification of the Soil and Water Assessment Tool (version 2005) that allows faster percolation through the soil substrate and recharge of the aquifer. This addition was necessary to simulate quick movement of water through vertical conduits that characterize karst topography. The model was calibrated for the James River Basin, a large watershed (3,600 km2) in Southwest Missouri. Losing streams were simulated by specifying high soil conductivities in the channels, and sinkholes were simulated as ponds with a high hydraulic conductivity at the bottom. Results indicated that the changes improved the partition of stream flow between surface and return flow. Water quality results indicated that the SWAT model can be used to simulate the frequency of occurrence of pollutant concentrations and daily loads. This case study highlights the possibilities and limitations in modeling flow and water pollutant movement in a karst watershed.