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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Research Project #430609

Research Project: Computational Tools and a Decision Support System for Management of Sediment and Water Quality in Agricultural Watersheds

Location: Watershed Physical Processes Research

2019 Annual Report

1. Provide accurate, efficient and user friendly multi-dimensional numerical models for studying (1) water driven soil erosion and sediment transport, (2) embankment breaching processes and associated flooding problems, and (3) agro-pollutant transport and water quality problems. (NP211 2016-2020 Action Plan: C2: PS 2.1; 2.2; 2.4; 2.5; C3: PS 3.1) 2. Develop a web-based Agricultural Integrated Management System (AIMS) that disseminates seamless geospatial data for modeling purposes and sustainable watershed management, and provides automated simulations of runoff, sediment, and agro-pollutant loadings for any watershed in the U.S. (NP211 2016-2020 Action Plan: C2: PS 2.4; C3: PS 3.1; C4: PS 4.1; 4.2; 4.3)

Sediment and agro-chemicals from agricultural watersheds and streams are transported into lakes and rivers where they degrade the aquatic eco-system and general water quality. The University of Mississippi, National Center for Computational Hydroscience and Engineering (NCCHE) has developed a number of computational models capable of simulating free-surface flows, soil erosion, embankment, levee and dam breaching, flood flows, sediment/contaminant transport, optimization analysis and decisions support systems for watershed management. These models have been rigorously verified and validated in previous research and are continuously being improved and upgraded. Computational modeling and effective decision support systems are needed in order to study problems and find solutions for soil erosion, gully erosion, sediment transport, embankment breaching and consequential flood inundation. NCCHE staff will work closely with the research scientists of the USDA to utilize these reliable and efficient models to study, understand and resolve the soil and water related problems in agriculture watersheds. At the same time, existing models need to be improved and enhanced by adopting new methods and merging technologies in order to better serve the needs of the agriculture research. The main focus of this project are issues of embankment breaching and flood inundation, detailed watershed runoff, erosion and pollutant transport, local scouring around instream structures, water quality and eco-systems affected by watershed, sediment transport optimal control, software efficiency improvements and decision support for watershed management. This research will help to achieve the goals of Water Availability and Watershed Management.

Progress Report
Water availability and sustainability are major challenges to our agriculture productivity and environmental quality. In Mississippi, the situation of the groundwater depletion in the Delta due to agriculture has drawn attention to water resource management and research community. The current rate of over-pumping is obviously non-sustainable. National Center for Computational Hydroscience and Engineering has started some research in this direction and developed a 3D groundwater model to assist current groundwater recharging study of the USDA. Improving computational modeling methods is one of our research focus areas. In this period, a new method to improve a key computation fluid dynamics modeling technique has been developed for better convergence and accuracy of free surface flow models. The topographic mapping method used in the mesh generator is further significantly improved and updated. The mapping time needed using the new mesh generator is reduced to a tiny fraction of that used before. New features have also built in the updated graphic user interface for the general public. In shallow inland lakes, hydrodynamic forcing is weak. The concentrations of dissolved chemicals and suspended sediments are almost uniformly distributed. The WQ constituents may also have vertical distributions because the solar intensity, temperature and suspended sediment have vertical distributions affecting the water quality processes. Considering these conditions, a vertical distribution (VD) model has been developed to simulate the WQ processes. Since the water depth in natural lakes varies, the VD model is further improved by dividing the entire lake automatically into multiple zones. The water depth of each zone is nearly uniform. The water quality process is computed within each of the zones and then redistributed to obtain a more reliable solution. The accuracy of the VD model developed earlier is thus further enhanced and its high efficiency feature is kept.