Modeling riparian buffer restoration impacts on water quality in the upper Green River watershed of Kentucky and Tennessee

Background/Question/Methods

Monitoring and modeling the impacts of implementing a Conservation Reserve Enhancement Program (CREP) in the Green River watershed of Kentucky, a program used to reestablish riparian corridors from pasture and cropland, has led us to develop a Soil and Water Assessment Tool (SWAT) model for the 400,000 ha area. The strengths of the USDA model, which focuses primarily on agricultural management practices and ecosystem processes using GIS data and analyses, are in representing flows, sediment, and nutrients in the watershed in conjunction with historical land use and changes in land use.  The primary goal of the conservation program is to improve water quality by reducing inputs of sediment, pesticides, and nutrients into the river system.

Results/Conclusions

The model we have refined for the upper Green River basin, including calibration, validation, and sensitivity analyses, is very effective at accurately representing water flows under a range of conditions. The SWAT flow model we developed showed 97% agreement with USGS measured flows. We have modified model flows to accommodate problematic karst drainage in regions where they are dominant or significant. Simulation experiments focused on sediment reduction found differences in sediment reduction effects at different scales that appeared to be dependent upon landuse, watershed size, and stream order. The model has also been used to evaluate nutrient reductions and storm events, where many stream inputs are mobilized. These modeling results are compared to historical water quality sampling results.