270 - Numerical Modeling of Flow, Sediment and Nutrients in Upland Watersheds and Downstream Channel Networks

The water quality in channel networks is influenced not only by the physical and chemical processes in the waterbody, but also significantly affected by the surrounding watersheds, which may produce large amounts of sediment, nutrients, and other pollutants. Linking information about upland watersheds and channel networks is critical for developing an effective approach to assess the causes of water quality issues and target solutions to improve water resource management. This paper presents a technical approach by integrating watershed and surface water models to simulate flow, sediment and nutrient processes throughout the entire system. The AnnAGNPS watershed model developed at the ARS National Sedimentation Laboratory, is applied to simulate the runoff, sediment and nutrients loads from upland watersheds. The outputs from AnnAGNPS provide inlet boundary conditions for the CCHE1D model developed at the National Center for Computational Hydroscience and Engineering (NCCHE), University of Mississippi, to simulate flow, sediment transport and nutrient distributions in downstream channel networks. The developed system was validated and applied to the Goodwin Creek Experimental Watershed in Mississippi. This technology provides a useful tool for evaluating water quality in both the upland watershed and the receiving water bodies. It can also be applied to assess the effectiveness of upland conservation management practices in improving water quality in downstream channel networks.