Project : USDA ARS

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Research Project: Managing Water and Sediment Movement in Agricultural Watersheds

Location: Watershed Physical Processes Research

2021 Annual Report

Objectives
1. Develop new knowledge and methodologies to quantify soil detachment and sediment transport, transformation, storage, and delivery. 1.a. Determine functional relations among variables (i.e., rainfall, soil moisture, soil texture, bulk density, organic matter, vegetation) with soil erosion. 1.b. Quantify the surface and subsurface processes controlling erosion and depositional features. 1.c. Quantify the effects of mixed-particle sizes and bed forms on roughness and sediment transport. 2. Improve knowledge of processes controlling surface and groundwater movement in agricultural watersheds, and their associated quantification. 2.a. Removed per approved Ad-hoc approval July 2018. See approved post plan. 2.b. Assess the use and management of floodplain water bodies for providing ecosystem services in order to support their use as a sustainable source of water for agriculture. 2.c. Quantify the processes partitioning components of the water budget in upland catchments of the Lower Mississippi River Basin. 3. Translate research into technology to quantify and evaluate management effects on watershed physical processes. 3.a. Develop a GIS-based erosion prediction management system that facilitates database acquisition and input file development, output visualization, and supports multiple scales of focus, including: watersheds, farm fields, and streams. 3.b. Develop technologies and tools to evaluate the benefits of conservation practice plans within and among fields, streams, and watersheds. 3.c. Develop new computer model components to simulate non-uniform sediment transport and stream morphologic adjustment at subreach scales. 4. As part of the LTAR network, and in concert with similar long-term, land-based research infrastructure in the Midsouth region, use the Lower Mississippi River Basin LTAR site to improve the observational capabilities and data accessibility of the LTAR network and support research to sustain or enhance agricultural production and environmental quality in agroecosystems characteristic of the Midsouth region. Research and data collection are planned and implemented based on the LTAR site application and in accordance with the responsibilities outlined in the LTAR Shared Research Strategy, a living document that serves as a roadmap for LTAR implementation. Participation in the LTAR network includes research and data management in support of the ARS GRACEnet and/or Livestock GRACEnet projects. 4.a. Develop the Lower Mississippi River Basin LTAR location addressing issues of long-term agroecosystem sustainability specific to the region, participating in the Shared Research Strategy, and contributing to network-wide monitoring and experimentation goals. 4.b. Enhance the LMRB CEAP watershed long-term data sets and integrate with other long-term data sets in the LMRB to address agroecosystem sustainability at the basin scale. 5. Increase knowledge and understanding of the processes governing movement, storage, and quality of water in the Mississippi River Valley Alluvial Aquifer, and develop technologies to enhance the sustainability of water resources for agriculture. 5.a. and 5.b. See approved post plan.

Approach
In the Lower Mississippi River Valley, groundwater extraction for irrigation has outpaced aquifer recharge, and precipitation is expected to fall in fewer, higher intensity events, thereby increasing runoff and stream peak discharges. This will impact erosion patterns and rates, destabilize streams with consequent loss of arable land, adversely impact ecosystem services, and reduce reservoir usability. These are not only regional but also national concerns. There is a critical need for improved understanding and quantification of the processes that control: the movement of water across the landscape; the detachment and transport of soil and sediment; and the morphologic adjustment of channels. This research will use an integrated approach to watershed management through the development and testing of innovative practices and computational models based on a scientific understanding of hydrogeomorphic processes at the test-plot, farm, watershed, and river-basin scales. Field and laboratory, short- and long-term experiments will be conducted to fill technology and knowledge gaps in USDA erosion models concerning: ephemeral gully and soil pipe erosion; transport of eroded sediments and of sediments introduced by reservoir sediment management actions; and stream system physical integrity. Findings will be used to develop new computer modeling components to optimize conservation measure design and placement for the RUSLE, AnnAGNPS, and CONCEPTS computer simulation models. Long-term monitoring combined with new field experiments will investigate the long-term sustainability of surface and groundwater resources in the Lower Mississippi River Valley.

Progress Report
Progress was made on all five objectives and their subobjectives, all of which fall under National Program (NP) 211. The construction of a new laboratory soil erodibility testing method was completed. Calibration of the erosive flow parameters of the test facility has been started. Complementary field experimentation to study gully erosion processes and control is ongoing. The field monitoring of the combined impacts of soil pipeflow and surface runoff on headcut migration were analyzed and journal publications were prepared. We made progress on experiments concerning the calculation of bed load using the modification of the bed forms in sand-bedded channels. This project was cooperative with researchers from the U.S. Army Corps of Engineers Waterways Experiment Station, Vicksburg, Mississippi. One of the major goals of this study was to quantify confidence intervals in the calculated bed load rates using this procedure. This goal was met along with others concerning the formation and dynamics of dunes on the bed of sand bedded channels. Progress has also been made on a series of experiments concerning the clean-out depth of sand in immobile gravel beds. A new series of field data collection was designed for the Goodwin Creek Experimental Watershed using the impact of gravel sediment on plates mounted on the bottom of the channel. This study will determine initiation and cessation of motion of gravel particles by grain size over a runoff year. Additionally, a hydrophone array was constructed for testing the measurement of direction and distance of Sediment Generated Noise (SGN) to determine bed load transport rates. The system was tested in the University of Mississippi swimming pool. Continued monitoring particle settling traps at Beasley Lake and Roundaway Lake to determine the seasonal variability in sedimentation rates of ponds in the Mississippi Delta. To study the erosion of levees around small irrigation reservoirs in the Mississippi Delta, we surveyed cross-section geometry of levee to document ongoing erosion at Johnson Reservoir, and installed and monitored an onsite weather station. Further, we installed approximately 200 meters of geotextile bank protection on the south levee to develop best management practices. The laboratory experiments and a publication on cable-restrained floating pipe breakwaters were completed. We made progress on further improving the USDA, ARS natural resources computer models AnnAGNPS, CONCEPTS, EphGEE and RUSLE2, and their integration. The USDA, ARS natural resources computer model AnnAGNPS was improved through integration with pesticide models focused on rice production and enhancements to better describe organic carbon, ephemeral gullies, on-farm water storage, glaciated landscapes, and basin systems. These features provide critical management tools to evaluate the most effective approach of implementing conservation practices applied within watershed systems needed in conservation management planning. The USDA conservation planning tool RUSLE2 has moved from the desktop to the cloud with improved dynamic erodibility and carbon sequestration modules. The RUSLE2 ephemeral erosion calculator (EphGEE) has been modified and is currently under calibration review using remotely sensed centimeter scale imagery. A final report comparing RUSLE2 soil loss estimates to those of the Water Erosion Prediction Project was delivered to ARS Headquarters. Using a combination of multi-dimensional computer models of different complexity, the evolution of dunes and bars on the bed of the Pearl River was examined. The findings were used together with results from high-resolution bathymetric sonar surveys to elucidate the interactions between river bed and planform adjustment. We made progress in developing the Lower Mississippi River Basin (LMRB) LTAR site through participation in national network activities, the establishment of new flux tower sites, and further development of the Common Experiment design for the LMRB site. The Water Information Systems by KISTERS (WISKI) is being used to enhance the collection, management, and analysis of precipitation, runoff, and sediment concentration data from the ARS Conservation Effects Assessment Program (CEAP) Goodwin Creek Experimental Watershed. We continued development of a novel pilot project for investigating managed aquifer recharge in the Mississippi Valley Alluvial Aquifer: (1) completed construction of the system, (2) established final version of rigorous sampling protocols for pre-operation water level and water quality data, (3) conducted monthly water sample collection for laboratory analysis, (4) completed shakedown of the system and began continuous operation of the facility for pumping/injection experiments; and (5) interacted with faculty and graduate students at the National Center for Physical Acoustics, National Center for Computational Hydroscience and Engineering, U.S. Geological Survey, and University of Mississippi departments of Civil Engineering and Geology & Geological Engineering who are analyzing some of the experimental data. The bathymetry and width of select reaches on the Little Tallahatchie River were quantified. In collaboration with the University of Illinois a database of stream geometric properties (width, depth, bottom topography, planform) is under development, and predictive technologies are being developed to estimate these properties using geography, soil, and land use information.

Accomplishments
1. Pesticide application in rice paddies has the potential to be harmful to ecological health of receiving water bodies. Thiobencarb is a commonly used herbicide in Northern California rice fields that may pose ecological risks to non-targeted organisms. Currently available models do not adequately represent the fate and transport of rice pesticides at watershed or basin scales. ARS researchers in Oxford, Mississippi, integrated rice pesticide transport technology at the field-scale with watershed-scale technology to follow the fate of pesticides throughout the watershed system. Application of the new technology to investigate the fate and transport of thiobencarb residues from paddy fields in the Colusa Basin, California, showed thiobencarb concentrations in both water and sediment phases were accurately captured at the edge of field. The integrated system accurately reflected both the seasonal pattern of surface runoff and the timing of monthly thiobencarb loadings downstream as well. The integrated technology successfully extends field level simulations to watershed scales while considering the impact of mixed land uses on downstream loads. This integrated modeling system provides technology to action agencies when evaluating rice pesticide load impacts as part of a basin level management approach to improve water quality.

2. Improved relationships between river planform and cross-section attributes. The understanding of the migration of river meander bends is incomplete because of highly complicated flow and sediment transport patterns, and resulting interactions between vertical and planform adjustment. Planform is typically represented by the curvature of the channel centerline, while point bars are the prominent features comprising the river bed. Combining analyses of aerial imagery and river bathymetry collected using unmanned aircraft systems and multibeam sonar, ARS researchers in Oxford, Mississippi, in collaboration with researchers from Louisiana State University and the University of Illinois developed relationships between channel centerline curvature and point bar geometry for select meander bends on the Wabash River, Illinois/Indiana, and the Pearl River, Mississippi/Louisiana. Additionally, an analytical model to estimate river bed geometry from channel centerline curvature was used to investigate the developed relationships. The temporal adjustment of planform and point bar geometry on both river systems was consistent for meander bends migrating in downstream direction. Specifically, the point bars presented a flat upper geometry, maximum migration rates occurred near the bend apex, and the bends developed a curvature comprising multiple maxima. These findings can be used in river engineering to determine rate and direction of future meander bend migration and channel depth. Action agencies will therefore be able to prioritize bank stabilization to protect farmland and irrigation infrastructure along meandering rivers.

3. Established baseline conditions for groundwater level and water quality for the Groundwater Transfer and Injection Pilot Project. The Mississippi River Valley alluvial aquifer (MRVAA) provides over 90% of the irrigation water used in the heavily agricultural Mississippi Delta region in northwestern Mississippi, with more than 20,000 irrigation wells supplying water to 1.8 million acres of cropland. Reliance on groundwater has resulted in consistent declines in MRVAA water levels over much of the region. ARS researchers in Oxford, Mississippi, developed the Groundwater Transfer and Injection Pilot Project (GTIP) to test the feasibility of withdrawing groundwater from near a large river and injecting the water into an area where the aquifer is depleted so that it can be used later for irrigation. The GTIP system was activated on April 15, 2021, and was operated continuously. Water level data from 17 monitoring wells were collected for at least nine months prior to the GTIP system entering the operational phase. Water quality data for a subset of 6 wells were collected for at least 7 months. Monthly physical samples were collected from over 20 sampling points and analyzed, including a set of samples collected just before the pumping began. A groundwater mound exceeding 6 ft formed near the injection wells, extending beyond a radial distance of 3,600 ft based on a small but steady rise in water level at this location. The data collected during this phase of the project will provide vital information needed for determining whether groundwater injection is a viable method for reversing declines in groundwater levels in the Mississippi Delta region. Agricultural producers, Mississippi Department of Environmental Quality, U.S. Geological Survey, U.S. Army Corps of Engineers, and other entities are keenly interested in the results of the project.

4. Conservation management planning agencies need information to guide planning activities and allocation of limited mitigation resources at regional scales. An integrated approach to analyze individual fields based on multiple management, landscape, and combined management-landscape conditions with links to larger scale analyses would be a valuable management tool. ARS researchers in Oxford, Mississippi, developed integrated watershed technology to characterize water and non-point source pollution at basin scales through integrated field-scale analyses providing optimization of computer resources at larger scales. The integrated technology was shown to provide similar results when applying individual simulations to smaller areas linked together compared to when simulating all the areas in one simulation. This study revealed the integrated approach is a viable option to increase computational efficiency when simulating large areas at high spatiotemporal resolutions. These tools provide capabilities to action agencies in performing national assessments of conservation practice effectiveness based on analyses of integrated results from individual agricultural fields throughout the U.S.

5. Flow history and transport of sand and gravel in streams. The rate of movement or transport of the sediment on the bottom of streams is information necessary to assess the net rate of erosion from upstream sources, determine the potential for erosion or deposition of the channel boundary, and ultimately to evaluate and predict the stability of the channel and watershed. ARS researchers in Oxford, Mississippi, conducted a series of experiments to determine the effect of recent flow history on the rate of movement of sand and gravel in a model stream channel. The effect of four different antecedent flows on the mean rate of sand and gravel transport for standard flows was evaluated and found to be related to the magnitude of the previous flow in the channel. This study indicates that the transport of coarse sediment in stream channels is not just a function of flow strength and sediment size but is also a function of flow history. Accurate bed load transport rates are critical for designing stable channels. This information is necessary for managers to evaluate and design sustainable watersheds to assure that fertility and productivity of the land is maintained.

6. Established field monitoring and experimental levee protection on irrigation reservoir. Irrigation reservoirs are a conservation practice for reducing dependence on groundwater for crop irrigation. Surface water is stored in the reservoirs during months with high precipitation and then used for irrigation in the summer, when crops need the most water. A common problem with the reservoirs is rapid levee erosion caused by wind-driven waves. ARS researchers in Oxford, Mississippi, initiated a field study at Johnson Reservoir near Shelby, Mississippi. A weather station was installed, levee cross-sections were surveyed, and geotextile bank protection was implemented for approximately 200 m of the south levee. In the near future, experimental floating wave barriers for reducing wave energy will be installed. The results of this work will be used for developing recommendations for reducing levee erosion for farmers who use irrigation reservoirs. Reducing erosion will make the levees last longer and reduce costs for levee repairs, which represent a barrier to using the conservation practice.

U.S. DEPARTMENT OF AGRICULTURE

Watershed Physical Processes Research: Oxford, MS