Integrated Numerical Modeling System for Upland Watersheds, Channel Networks and Downstream Waterbodies

Abstract Submission: The water quality of receiving waterbodies is significantly impacted by upstream channels and land use, which can contribute substantial amounts of sediment, nutrients, and other pollutants. Integrating information from upland watersheds, channel networks, and receiving waterbodies is essential for developing an effective water quality management strategy for the entire watershed-waterbody system. This paper presents a technical approach that integrates watershed, channel network, and surface water models to simulate flow, sediment, and water quality processes throughout the system. The AnnAGNPS watershed model, developed by the USDA Agricultural Research Service (ARS) National Sedimentation Laboratory, is employed to simulate runoff, sediment, and nutrient loads from upland watersheds. The outputs from AnnAGNPS provide inlet boundary conditions for the CCHE1D model, developed by the National Center for Computational Hydroscience and Engineering (NCCHE) at the University of Mississippi, which simulates flow, sediment transport, and nutrient distributions within downstream channel networks. Subsequently, water quality constituents in the receiving waterbody are simulated using CCHE-WQ, based on the CCHE1D model results. This integrated modeling system was validated and applied to the Upper Pearl River Basin (UPRB) in Mississippi, which includes a large upland watershed (~7,000 square kilometers), major rivers (the Pearl River, Yockanookany River, and Tuscolameta Creek), and the downstream Ross Barnett Reservoir. This study provides a valuable tool for evaluating water quality across the entire watershed-waterbody system and can also be used to assess the effectiveness of upland conservation management practices in improving water quality in downstream waterbodies.

Learning Objectives/Expected Outcome (Optional) :