Simulating nonpoint source pollutant loading in a karst basin: A SWAT modeling application

Karst terrain confounds efforts to parameterize and calibrate The Soil Water Assessment Tool (SWAT). purpose of this study was use SWAT simulate long-term natural (e.g. climate) human land use) impacts streamflow, sediment nutrient loading in a karst catchment. Sub-objectives were to: (1) perform rigorous model performance assessment SWAT, (2) apply highlight critical source areas NPS pollutant large (HUC-8 spatial scale) basin the central USA. Long-term (25-years) daily streamflow data collected at seven nested U.S. Geological Survey flow gaging sites used validate SWAT. Annual estimates spring contributions from dominant springs disintegrated timeseries' dependent on baseflow separation results calculated observed data. Model calibration showed percent bias (PBAIS) ranged 1.1 19.3%, Nash-Sutcliff efficiency (NSE) values 0.25 0.63. validation PBIAS −5.1 −32.8%, NSE 0.44 0.78. Results highlighted potential pasture sources. Simulated overland (i.e. not including channel processes) sediment, TN, TP yields 108 Mg km−2 yr−1, 14.1 kg ha−1 0.68 respectively, HUC-8 scale. greatest N P associated with waste water treatment plant (WWTP), WWTP persisted over 100 km downstream ultimately accounting for approximately 37% outlet. have implications end users tasked creating physically realistic models watershed hydrology using point an ongoing need improved sub-surface storage routing modeling routines.