Environmental and economic analysis of using SWAT to simulate the effects of switchgrass production on water quality in an impaired watershed

Abstract

Future bioenergy demand will likely result in the conversion of significant amounts of crop and pasture/hay lands in the mid-south of US. The objective of this research is to analyze the effects of the large-scale land use conversion to switchgrass as a bioenergy feedstock on water quality and economic feasibility in Oostanaula Creek watershed in East Tennessee. The soil and water assessment tool (SWAT) model was first used to simulate nutrient loadings of current land use in the watershed. Statistical criteria such as Nash–Suttcliffe efficiency (E) and R2 were calculated for model calibration and validation. The calibrated SWAT model was then used to simulate the effect of the land use conversion from the entire current crop and pasture/hay lands to switchgrass production. Results show that the conversion reduces average annual watershed loadings of sediment, nitrate (NO3), total nitrogen (TN), and total phosphorous (TP) by an estimated 77%, 62%, 34%, and 46%, respectively. Analysis of net present values of ten years of farm profits and cost-effectiveness ratios for abatement of nutrient loadings indicates that the land use conversion is economically feasible.