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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

2020 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
Watershed is a basic topographic unit which dominates hydrological processes and affects agriculture practices and management. Accurate and effective ways of delineating detailed channel networks are essential to watershed process modeling. In this study period, a simple and effective algorithm for automatically identifying and extracting watershed channel networks is proposed. The proposed algorithm used a unique watershed-merging method to connect the neighboring sub-watersheds. Currently available methods need to adjust local topographic elevation to handle the network connections. The newly developed method preserves original topographic digital elevation model (DEM) data without any adjustments. Computing code based on this method has been implemented and tested. Applications of generating channel networks using multiple real-world watershed topographies demonstrated that the results of the proposed algorithm were very good, and consistent to those using the well-established model, TOPAGNPS. This development provides an optional method to delineate watershed topography and channel network for watershed hydrology, soil erosion and water quality and agriculture management models. Further improvements to this newly proposed method are necessary, particularly its computation-intensive merging process will be accelerated through optimization techniques. Water quality of inland lakes are affected by the hydrology and agriculture management of their watersheds. When rainfalls of strong storms are too much, inland lakes, particularly those oxbow lakes in the Mississippi Delta, can be flooded. In recent years, the Beasley lake, was flooded multiple times by the flood water of its downstream SunflowerRiver. The stages of Sunflower River were so high, it flaw backward and flooded the Beasley Lake and farmlands of the lake watershed. The agriculture lands in Beasley Lake watershed have conservation measures to control soil erosion and nutrient loss. The backwater of Sunflower river was from less conserved areas, and thus, may affect the water quality of the Beasley Lake. The study includes two parts: flooding and water quality. Initial numerical study has shown the flood stage of the Sunflower River in spring 2019 rose higher and higher, and backed into the Beasley watershed and Beasley Lake, inundated a large area of farmland. The flood water retreated days later. The simulated flood process and flow fields are analyzed and will be used later to study the impacts on the lake water quality. Soil erosion from agriculture watersheds results in soil and nutrient loss, and forms gullies on land surface downgrading the productivity and cultivability. These processes can be better simulated using physically based models with high resolution meshes. The physically based CCHE2D model has been validated using measured runoff velocity and water depth data in experimental watersheds of different soil, topography and rainfalls. The model is further improved to simulate watershed soil erosion and gully erosion, using the experimental data quantitatively measured in a large experimental facility by the National Sedimentation Laboratory. This developed CCHE2D model was validated using field watershed data measured in the Beasley watershed, Mississippi, by U.S. Geological Survey. The numerical model with a high-resolution mesh simulated the rainfall-runoff hydrology, rainfall splash erosion, runoff surface erosion and channel flow erosion. The agreements of simulated and measured runoff and sediment hydrographs are quite satisfactory. In addition, the CCHE2D model has implemented a unique non-isotropic surface resistance algorithm to compute farm field runoff influenced by tillage rows. Because the local elevation variation of the land surface with tillage rows is much larger than runoff depth, the runoff trends to flow along the row direction rather than the general hillslope direction. The apparent resistance in the row direction is thus smaller than that across. The updated model is tested in a farmland in the State of Iowa. The land topography was obtained using the high precision method of air-photometry by the National Sedimentation Lab, USDA. Numerical simulations showed that when the mesh size is much less than the row spacing, isotropic resistance is feasible; when the mesh size is comparable to or larger than row spacing, the non-isotropic resistance method should be applied for good results. A new method improving the computational fluid dynamics (CFD) simulation models is proposed and tested using analytic and practical cases. In many CFD models for solving free surface flows, sediment transport and pollutant transport an important step involves calculating the control volume surface value of velocities between solution points called momentum interpolation. This method prevents numerical oscillation and simplifies simulation methods. We have developed an improved interpolation method that considers the complete flow field information surrounding the interpolation point. Numerical tests indicated that the new method has more accurate solutions and converges faster than the popular conventional method. Because this is a general improvement to the widely applied momentum interpolation methods, it provides an effective approach to CFD modelers to enhance their models. A large amount of groundwater has been pumped and used for agriculture in the State of Mississippi. The resulted groundwater depletion in the Mississippi Delta has drawn a great attention to water resource management and research community because the rate of over-pumping is obviously non-sustainable. The National Center for Computational Hydroscience and Engineering (NCCHE) has started groundwater research and developed a 3D groundwater model to assist the groundwater study led by research scientists of National Sedimentation Lab, USDA-ARS. The 3D groundwater model has been applied in Money County, Mississippi, at a site near the Tallahatchie River. Using measured geological conditions of the aquifers and hydrological conditions of the Tallahatchie river, the model successfully simulated the ground water depletion process caused by pumping and surface water-groundwater interaction. The developed groundwater model has a good potential to contribute to the Mississippi Delta groundwater recharging project of USDA. Water resources are often polluted by agriculture, industry and urban pollutants. Aquatic ecosystem would also deteriorate by excessive agro-pollutants. 2D and 3D numerical models are developed, improved and applied to study the process, distribution and impacts of the pollution events in waterbodies such as rivers, lakes and coasts. Applications of the improved and refined models revealed water quality processes and problems in multiple water bodies in the U.S. and other countries. CCHE3D has been applied to study the water quality process in the Pelahatchie Bay, Ross Barnett Reservoir in Mississippi. The water quality of the bay has been degraded by sediment and nutrients from its watershed and the limited flow exchange between the bay and the main Ross Barnett Reservoir. The CCHE2D model has been applied to simulate multiple flood release events in recent years from the Mississippi River to Lake Pontchartrain, Louisiana. Because of the flood releases have greatly changed the water quality and eco-environment of the lake, algal blooms and oyster extinctions were occurred. Numerical simulations predicted the flood releasing processes and associated flow field variation, sediment transport, salinity, and nutrient level in the lake. These studies revealed the natural responses of the coastal lake to the flood release events and provided tools to mitigate the negative impacts. A web-based Agricultural Integrated Management System (AIMS) has been developed for watershed conservation management planning. This technology provides watershed process and agriculture management modeling with automated data preparation from seamless geospatial data for any watershed in the U.S. Many updates and improvements of software were made because of updates of the main server and many associated hardware. One of the main objectives of AIMS is the preparation of geospatial data layers. Among others, soil and cropland data are required to be updated. In addition, climate data and management data are needed for the AnnAGNPS model of the USDA. Capabilities of acquiring climatological data from nearby weather stations and approximate dominant crop type for watershed cells were developed. To test the consistency of the overall system, a test case was developed to simulate the watershed hydrology process and agriculture management using this web-based model.

1. A new modeling approach for soil and gully erosion research. A novel 2D numerical simulation model has been developed by ARS researchers in Oxford, Mississippi, to simulate soil erosion and gully erosion processes in field sized watersheds. This physically based model mimics rain storm induced watershed runoff, splash erosion, shear erosion of soil and sediment transport processes in high resolutions. The simulation results have been validated using experimental and field observation results collected by Federal agencies. This new capability helps hydrology and agriculture engineers in erosion control research. This provides the Natural Resources Conversation Service (NRCS) a powerful tool that will help evaluate ephemeral erosion throughout the country.

2. A 3D groundwater model assisted Mississippi Delta groundwater recharging project. A 3D groundwater simulation model has been developed by ARS researchers in Oxford, Mississippi, and applied to simulate the groundwater depletion and recharging processes. Using measured geological conditions of the ground layers and hydrological conditions of the Tallahatchie river, the model successfully simulated the ground water depletion process caused by pumping and surface water- groundwater interaction. The model and its application provide key information to Mississippi Delta groundwater recharging project.

3. A new Momentum Interpolation Correction method for CFD models. Momentum interpolation is an important method widely applied in computational fluid dynamics (CFD). A novel assumption that the momentum interpolation is applicable not only at the edge, but also around the edge of computation cells, is proposed by ARS researchers in Oxford, Mississippi. According to the test example cases, in general the new method showed accelerated convergence and improved accuracy, especially for cases with irregular cells and domain geometry. The new method will enhance efficiency and accuracy of CFD models and benefit CFD applications.

4. A semi-automatic mesh generator for irregular domains. ,Mesh generation is an essential step to carry out numerical simulations. It often takes time to generate a quality structured mesh for irregular domain of water resource problems. ARS researchers in Oxford, Mississippi, proposed a new algorism to automatically generate structured meshes to save time. Modelers will have more time working on their numerical simulation and result analyses. Test cases indicated that most meshes can be generated automatically, only a little assistance is needed if the shape of the domain is very complex. The new mesh generator makes the mesh generation a much easier work for water resource engineers.

5. Developed modeling capabilities for simulating river morphologic change. Natural rivers have flood and sedimentation processes that changes the river bed and bank morphology. The CCHE2D and CCHE3D models, developed by ARS researchers in Oxford, Mississippi, have the capability to effectively simulate these processes and help river engineers study river flooding, sedimentation processes and geomorphology. Collaborations of research scientists of Chinese Academy of Sciences, Taiwan and the National Center for Computational Hydroscience and Engineering (NCCHE) and applications to river sedimentation processes have found these tools are effective.

6. Developed and applied numerical models to study water quality of water resources. Water resources are often degraded by agriculture, industry and urban pollutants. Aquatic ecosystem would also deteriorate triggered by agro-pollutants. 2D and 3D numerical models are developed and applied to study the process, distribution and impacts of the pollution events in waterbodies such as rivers, lakes and coasts. Applications of the developed models revealed nutrient transport, sediment transport, dissolved oxygen and eutrophication processes in multiple water bodies in the U.S. and other countries.

Review Publications
Yafei, J., Yaoxin, Z., Keh-Chia, Y., Chunf-Ta, L. 2020. Modeling river morphodynamic process using a depth-averaged computational model and an application to a mountain river. Intech.
Zhang, Y., Jia, Y. 2019. Velocity correction coefficients in pressure-correction type model. American Society of Civil Engineers Journal of Hydraulic Engineering. 145(6).
Jia, Y., Zhang, Y., Chen, D., He, L., Termini, D. 2019. Modeling bedload transport trajectories along a sine-generated channel. Water Resources Publication. 46(4): 542-552.
Liu, G., Zheng, F., Jia, L., Jia, Y., Zhang, X.J., Hu, F., Zhang, J. 2019. Interactive effects of raindrop impact and groundwater seepage on soil erosion. Science of the Total Environment. 578.