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Numerical simulation of flow, sediment and nutrients in upland watersheds and downstream channel networks
Proceedings of the 2023 Mississippi Water Resources Conference
Year: 2023 Authors: Chao X., Al-Hamdan M., Bingner R., Zhang Y., Witthaus L.
Goodwin Creek Experimental Watershed (GCEW) located in Panola County, Mississippi, is a 21.3 square kilometers Conservation Effects Assessment Project (CEAP) benchmark watershed monitored by USDA-ARS National Sedimentation Laboratory (NSL). The main concern in this watershed is soil erosion due to rainfall and runoff in the upland fields. In addition, the sediment associated nutrients are also transported into downstream channel networks due to soil erosion. The Annualized Agricultural Non-Point Source (AnnAGNPS) watershed model, developed at the NSL, was applied to simulate the loads of water, sediment and nutrients from the upland fields of GCEW. In this model, the effects of land use/land cover, soil properties, climate, agriculture management, etc. on the watershed loads were considered. The results produced from AnnAGNPS were used as boundary conditions for the Center for Computational Hydroscience and Engineering 1-Dimensional (CCHE1D) model developed at the National Center for Computational Hydroscience and Engineering, to simulate the flow, sediment, and nutrients in downstream evolving channel networks of GCEW. This model computes the non-equilibrium sediment transport with non-uniform size mixtures. It can also simulate the transport and fate of nutrients and other pollutants in channel networks, including the biogeochemical reactions that take place in the streams and sediment bed layers. Simulated results were calibrated and validated using field measured data collected by the NSL. This research provides useful tools to assess the impacts of upland sediment and nutrient loads on the downstream channel networks.