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Abstract

Suspended sediment plays a vital role in coastal zone carbon and nutrients dynamics by supplying particulate carbon and nutrients from highland waters to the coasts through river systems. Human activities like reservoir management could fundamentally modify the sediment transportation processes. However, effective representation of sediment is missing in most existing land surface or earth system models, let alone the effects of reservoirs on sediment processes. We introduce a physically based river sediment module into MOSART-WM, which includes process-based parameterizations of: 1) hillslope soil erosion and discharge into streams; 2) sediment erosion, suspension and transportation through river networks; 3) reservoir regulation based on the inflows from upstream areas and water demand from downstream areas; and 4) sediment trapping by reservoirs. This new sediment module, denoted as MOSART-sediment, is developed within E3SM and to be applied to the river networks at the regional or global scales. Model application and validation will be carried out in the contiguous U.S. using historical streamflow and sediment observations from USGS. The relative contribution of reservoir trapping mechanism and flow regulation on riverine suspended sediment processes will be isolated and quantified through hypothesis-driven numerical experiments. This new sediment module lays the foundation for modeling transportation and transform of particulate C, N and P through rivers into the coastal zones and then the open ocean to help close the global C, N and P cycles.

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