Location: Watershed Physical Processes Research
2021 Annual Report
Objectives
1. Provide accurate, efficient and user friendly multi-dimensional numerical models for studying:
1.1. Water driven soil erosion and sediment transport.
1.2. Embankment breaching processes and associated flooding problems.
1.3. Agro-pollutant transport and water quality problems.
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.
2.1. Development of the AIMS portal with user access management system and geospatial map server with graphical user interface (GUI), and its maintenance.
2.2. Preparation of geospatial data layers to be provided for both dissemination and use in models for sustainable watershed management implemented in AIMS.
2.3. Adapting TopAGNPS and AnnAGNPS to improve their performance on the web-based, multi-user environment of AIMS portal.
2.4. Adaptation and implementation of BMPTOOL (Best Management Practices Tool), IWMTool (Integrated Watershed Management Tool) and CCIT (GIS-Based Cover crop Implementation Tool) under AIMS portal.
Approach
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
Progress was made on the two objectives and their subobjectives, all of which fall under National Program (NP) 211.
Channel network delineation is important for one-dimensional models when simulating water flow, sediment and pollutant transport processes from sub-watersheds to downstream. A new channel network delineation model using the newly developed watershed-merging method has been developed, which can be used for delineating channel network in watersheds based on digital Elevation Models (DEM). The model is further refined with improved computing efficiency. Multiple watershed examples ware used for testing which provided satisfactory results. This new capability substantially broadened the applicability of the CCHE1D model to hydrodynamic processed at watershed scale. In addition, the preliminary integration of this method into CCHE1D-GUI for personal computer (PC) based applications has been completed. The network generation model will also serve as a pathway for the integration of the CCHE1D model to the web-based decision support system, AIMS, and the agriculture process and management model, AnnAGNPS, in the future.
Mesh generation is a fundamental step to discretize mathematical equations and set up numerical simulations. The new CCHE-MESH version 5.0 with the automatic mesh generation algorithm and the efficient bed interpolation algorithm using a fast sorting approach has been developed. The automatic mesh generation algorithm was further refined by error fixes. The efficient bed interpolation algorithm was coded with two versions: one embedded into CCHE-MESH in VisualC++ (VCII) and the other as stand-alone executable tool in Fortran 95. With the above two techniques, the new CCHE-MESH can provide more efficient and easier mesh generations in complex geometries.
The momentum interpolation method is used in many computational fluid dynamics (CFD) models to calculate the face velocities and fluxes at the edges of control volumes. This approach eliminates numerical oscillations when solving free surface flows, sediment transport and pollutant transport problems. A new momentum interpolation scheme has been developed by including more information surrounding the cell surface. The new scheme out-performs those currently adopted in many other models in both accuracy and converging rate. Multiple test cases including physical experiments and field applications demonstrated that in general more accurate results and faster convergence speed can be obtained.
Groundwater is an important resource for agriculture. A three-dimensional (3D) groundwater model (CCHE3D-GW) has been developed, verified and applied to simulate the groundwater depletion processes resulted from a pumping tests near the Tallahatchie River in the Mississippi Delta. The simulations results and the field measurements by USDA and US Geological Ssurvey (USGS) scientists compared fairly well. The CCHE3D-GW model is further applied to the groundwater pumping and recharging test to investigate the behavior and distribution of the groundwater under this condition and evaluate the effectiveness of the recharging project. A novel method is developed to identify the temporal variation of the hydraulic conductance of a stream bed using observed stream flow, groundwater level and aquifer’s information. Preliminary tests indicated that the identified stream bed conductance varies in time, instead of constant used in most of applications. The predicted groundwater level can be more accurate if the identified stream bed conductance is used in numerical simulations.
After validations using soil erosion processes observed in experimental watersheds, different soil, topographies and rainfalls measured in the field of Beasley lake watershed, Mississippi, by USGS, have been used to test the CCHE2D soil erosion model. The model is recently applied to simulate a cornfield watershed in the State of Iowa with high-resolution topography obtained using the high precision method of air-photometry by the National Sedimentation Lab, USDA. The tillage ridges, furrows and gullies of the watershed, even the wheel tracks of spray rig tractors, were resolved. The model simulated detailed rainfall erosion, runoff erosion and deposition and gully erosion effects in this watershed with complex corn-field micro-morphology. It was found in a collaborative research in China that the rainfall impact on runoff surface can increase the sheet flow resistance. This finding benefited the numerical simulations of watershed soil and gully erosion process.
CCHE-WQ model and the Annualized Agricultural Non-Point Source (AnnAGNPS) model have been linked to study the water quality constituents in Beasley Lake in Mississippi Delta. The runoff and loads of suspended sediment (SS) and nutrients from upland watershed were simulated using AnnAGNPS model. CCHE-WQ model can take the outputs of AnnAGNPS for simulating the water quality in the lake. The effects of upland watershed on the lake water quality were studied.
CCHE3D water quality model has been integrated into CCHE-GUI and tested using Beasley lake case. The 3D wind-induced flow circulations were simulated and water quality constituents were obtained. It can be found that the concentration of chlorophyll showed strong 3D distributions.
The water quality of the coastal lake, Lake Pontchartrain in Louisiana, has water quality problems due to the flood release of Bonnet Carré Spillway from the Mississippi River. The flood releases decrease the salinity and increase the sediment concentration to a large extent, and disturb the aquatic environments. CCHE water quality model was applied to systematically simulate the dynamic process of hydrodynamics and associated temporal and spatial distributions of sediment, salinity and phytoplankton in Lake Pontchartrain using multiple flood release events.
Beasley lake watershed empties into the Sunflower River in the Mississippi Delta. In recent years, the floods in the Sunflower river are exceptionally high. The land and the lake of this watershed were flooded multiple times by the backward flood of the Sunflower River. The backwater of Sunflower River would affect negatively the water quality of the Beasley Lake and the surrounded farmlands because the flood water was from areas with less or no best management practice(BMP). CCHE2D-Flow models have been applied to simulate the flooding processes in the flooding zone. It has been proposed to study the water quality and pollutant transport in the lake and the farmlands due to the flooding events.
Accomplishments
1. A new modeling approach for soil and gully erosion research. A novel two-dimensional (2D) numerical simulation model has been developed to simulate soil erosion and gully erosion processes in watersheds at field scale. 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 observations. The tests indicated that the detailed erosion, deposition process caused by rain splash and runoff over tillage ridges, furrows and gullies could be resolved. This new capability helps hydrologists and agriculture engineers in erosion control research, and provides a powerful tool to NRCS 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 and applied to simulate the groundwater depletion and recharge 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. Application of the model to various combinations of groundwater extraction and recharge scenarios is underway, which will demonstrate the effectiveness of artificial recharge by injection to a depleted aquifer. The model and its application will provide key information to the managed aquifer recharge project of USDA-ARS in the Lower Mississippi River Basin.
3. A new delineation tool. Channel network identification and delineation is important to not only hydrologic analysis but also hydraulic analysis. The D8 algorithm with the steepest slope calculation is often used to delineate a DEM for channel network identification. One major difficulty of D8 algorithm lies in the depressions and flat areas where the slope calculation cannot correctly determine the flow direction. The conventional method for delineation of the depressions and flat areas is to revise the DEM by “filling” or “breaching” to make it “hydrologically correct”. The new watershed-merging method considers the depression and flat area “as is” and uses the local surrounding cell information, as well as the neighboring watershed information to determine the flow direction. The resulting flow routes can maintain the original topographical characteristics and accurately represent the channel networks.
4. A new Momentum Interpolation Correction method for CFD models. Momentum interpolation is an important method widely applied in computational fluid dynamics (CFD). It includes a novel assumption that the momentum interpolation is applicable not only at the edge of a control volume cell but also around the edge. This idea has been implemented in a finite volume model and tested. According to the test example cases, in general the new method is able to accelerate computations, especially for cases with irregular grid cells and complex domain geometry. The new method will enhance efficiency and accuracy of CFD models and benefit CFD applications.
5. CCHE-MESH 5.0 has been released. A semi-automatic mesh generator has been developed for irregular domains and fast bed interpolations. Mesh generation is an essential step to discretize governing equations and carry out numerical simulations. It often takes time to generate a high-quality structured mesh for an irregular domain in water resources problems. A new algorithm was proposed to automatically and efficiently generate structured computational mesh. 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. In addition, bed interpolation involves heavy-duty searching and computations especially for relatively larger domains with fine meshes. The proposed fast interpolation algorithm significantly improves interpolating efficiency. The new mesh generator is now integrated with the fast bed-interpolation model, making the mesh generation a much easier work for water resource engineers.
7. Applied numerical models to study water quality of water resources. Water resources are often polluted by agriculture, industry and urban pollutants. Aquatic ecosystem would also deteriorate triggered by agro-pollutants. The developed 2D and 3D numerical models have been applied to study the process, distribution and impacts of the pollution events in waterbodies such as rivers, lakes and coasts. The model has been particularly applied to simulate multiple flood release events and the impacts of flood releases from the Mississippi River to the Lake Pontchartrain on the lake water quality. The applications of the developed models revealed water quality processes and problems in multiple water bodies in the US and other countries.
8. Rainfall impact on runoff flow resistance. Soil erosion is one of the major problems in agriculture by deteriorating farmlands and polluting water resources. Raindrop splash plays an important role in detaching soil from land surface. Collaborated with scientists in China, this study revealed that raindrops can also impact the surface runoff, disturbing the flow structure and increasing the flow resistance. Multiple experiments have been conducted to collect a wide range of data and extract empirical relationships between rainfall intensity, runoff depth, Reynolds number and flow resistance coefficients. The study improved our understanding of hill-slope hydrological processes, and provided measured data and empirical relationships for hydrologist and water resource engineers to accurately analyze and simulate soil erosion processes.
9. A web-based Agricultural Integrated Management System (AIMS) has been developed for watershed conservation management planning. Agricultural Integrated Management System (AIMS) is a powerful watershed conservation management planning tool in easy to use technology. This technology provides modeling capabilities with automated data preparation from seamless geospatial data for use in evaluating runoff, sediment, and agro-pollutant loadings for any watershed in the U.S. via a Web-browser. Currently the test version of AIMS is capable of running TopAGNPS, and AnnAGNPS with some restrictions. The migration of the AIMS platform to the new machine equipped with Debian 9 (9.9.0) was completed. A brand new testbed server on a new operating system was created, and configured for secure on-campus network access. All of the essential software packages were updated and tested. A series of variable and library updates were made to run TopAGNPS on the new machines. New frontend and backend scripts required to add AnnAGNPS functionality to AIMS were developed. AnnAGNPS button enables to user to execute a series of two automated TopAGNPS runs and an AnnAGNPS run. In addition, several bug fixes were performed and documented on the server. The geospatial data layers including soil, climate and management data layers were updated. One of the main objectives of AIMS is the preparation of geospatial data layers. A case study was performed on the Johnson Creek-Long Creek HUC 12 Watershed (155.85 km2) located in Panola County, in northwest Mississippi. The AIMS system successfully prepared data files with minimum user intervention and ran the simulations.
Review Publications
Ozeren, Y., Wren, D.G., Reba, M.L. 2021. Wave-induced erosion of soil embankment in in laboratory flume. Journal of Hydraulic Engineering. 147:04021011.
Rossell, W., Ozeren, Y., Wren, D.G. 2021. Experimental investigation of a moored, circular pipe breakwater. Journal of Waterway, Port, Coastal and Ocean Engineering. 147(5):04021019.
Rebillout, L., Ozeren, Y., Altinaker, M. 2020. Dam-break flow measurements of liquid-granular mixtures in a channelized reservoir. Journal of Hydraulic Engineering. 146(12):04020080.
Zhang, Y., Jia, Y. 2020. Watershed-merging: A simple and effective algorithm for channel network identification and extraction. Water Resources Research. 56.e2019WR026943. https://doi.org/10.1029/2019WR026943.
Shen, E., Liu, G., Jia, Y., Dan, C., A.M.Abd Elbasit, M., Liu, C., Gu, J., Shi, H. 2020. Effects of raindrop impact on the resistance characteristics of sheet flow. Journal of Hydrology. 592:125767. https://doi.org/10.1016/j.jhydrol.2020.125767.
Chao, X., Jia, Y., Hossain, A., Zhang, Y. 2021. Numerical simulation of sediment transport, phytoplankton biomass and salinity recovery processes in Lake Pontchartrain due to Bonnet Carre Spillway flood release. Ecological Engineering. 160: 106151. https://doi.org/10.1016/j.ecoleng.2021.106151.
Ding, Y., Ding, T., Rustin, A., Zhang, Y., Jia, Y. 2020. Simulation and prediction of storm surges and waves using a fully integrated process model and a parametric cyclonic wind model. Journal of Geophysical Research: Oceans. 125.e2019JC015793. https://doi.org/10.1029/2019JC015793.
