Modeling seasonal sediment yields for a medium-scale temperate forest/agricultural watershed

As vegetation cover senesces across temperate watersheds, the potential for soil erosion and subsequent sediment yields increases. Despite the importance of vegetation dynamics and evapotranspiration towards influencing watershed-scale hydrological processes, limited research has fully included these variables in modeling sediment yields, relying on surface runoff records alone. Focusing on the Upper Floyds Fork watershed, Kentucky, we applied a multi-objective approach utilizing MODIS-derived estimations of vegetation and evapotranspiration (ET) to calibrate the Soil and Water Assessment Tool (SWAT) towards modeling seasonal sediment yields May 2019-April 2020. Results generated satisfactory error measures across all four variables (vegetation cover, ET, runoff, sediment). Above average precipitation and elevated erosive storm activity generated significant sediment yields even during months of greater vegetation coverage. Conversely, below average precipitation during Aug-Sep resulted in minimal sediment yields despite diminishing vegetation coverage. While precipitation acted as the dominant process controlling sediment yields, higher yields were also predicted in sub-watersheds as a function of steeper slopes, higher soil erodibilities and increased agricultural land cover during the dormant winter period. These findings may help identify when to expect increased sediment loads towards targeting specific sub-watersheds in managing future soil erosion, and defining and establishing best management practices in the future.