Data for "Development of a SWAT+ model to improve conservation practice efficacy for protecting stream health in karst pasturelands"

Placing appropriate conservation practices in the proper locations can benefit stream health in karst environments that are susceptible to agricultural pollution. Watershed models, such as the Soil and Water Assessment Tool+ (SWAT+), can optimize both practice selection and placement in the landscape, but to our knowledge no studies have tested this tool in karst pasturelands. We built a SWAT+ model for four watersheds in the southern Appalachians of Virginia — an area with extensive pasturelands and karst topography. SWAT+ predicted that streamflow estimates were most affected by setting the available water capacity to zero and increasing the hydraulic conductivity of the soil, revealing that water, and associated pollutants, move primarily through subsurface pathways. Predicted sediment yield was negatively associated with agricultural land cover and was strongly influenced by channel erodibility — indicating that the predominant sediment source may be streambanks. The model unsatisfactorily predicted total nitrogen and total phosphorus loads. Based on the pollutant dynamics revealed by SWAT+, practices that stabilize stream banks (e.g., fencing cattle out of streams) would be most effective at reducing sediment loads. The utility of SWAT+ for cattle grazing operations in karst regions could be improved by more accurately representing the effects of cattle grazing on streambank erosion and the dynamic subsurface movement of nitrogen and phosphorus.