Location: Watershed Physical Processes Research
2022 Annual Report
Objectives
1. Develop technologies to effectively manage surface water and groundwater resources in the Lower Mississippi River Basin.
1.A. Evaluate aquifer storage and recovery (ASR) for increasing groundwater supply in the Lower Mississippi River Basin.
1.B. Develop databases and computer modeling technologies to manage surface and groundwater resources for sustainable irrigated agriculture in the Lower Mississippi River Basin.
2. Develop and improve technologies to conserve soil and effectively manage erosion and sediments for a range of scales including plot, field, channel, and watershed scales.
2.A. Quantify the effects of soil physicochemical, geographic and hydro-climatic conditions, and soil conservation measures on soil erodibility and health.
2.B. Investigate the transport and fate of sediments eroded from farm fields and channels in agricultural watersheds.
2.C. Develop computer model components to improve assessment of soil and sediment management practices from field to watershed scale.
3. Evaluate management impacts on landscape evolution and processes in support of the national CEAP and LTAR networks.
3.A. Evaluate the multi-scale impacts of soil and water conservation practices.
3.B. Contribute databases and models to evaluate the long-term sustainability of agroecosystems.
3.C. Enhance and analyze the Goodwin Creek Experimental Watershed long-term data sets.
Approach
This Research Project addresses: (1) stresses on the Nation’s soil and water resources by increased agricultural water demand, agricultural intensification, and a changing climate; (2) impacts of groundwater withdrawals from the Mississippi River Valley Alluvial Aquifer on the integrity of the regional agroecosystem; and (3) limitations in knowledge and tools to assess management and climatic effects on watershed physical processes at plot, farm, watershed, and river-basin scales. We will use an integrated approach to watershed management through the development and testing of innovative practices and computational models based on scientific understanding of multi-scale hydrogeomorphic processes. Specifically, we will evaluate the feasibility of aquifer storage and recovery to provide reliable groundwater supply for irrigated agriculture on the Mississippi Alluvial Plain, and develop databases and computer modeling tools to assess surface water and groundwater resources management in the region. We will combine field and laboratory, short- and long-term experiments to fill technology and knowledge gaps in USDA erosion models concerning soil erodibility characterization, erosion and control of ephemeral gullies and earthen embankments, and transport and fate of eroded sediments. Long-term research and computer model development will investigate the long-term sustainability of agroecosystems. Project outcomes will provide critical information and tools to federal, state and local agencies to: (1) sustainably manage water resources in the Lower Mississippi River Basin, and (2) reduce soil loss and manage sediment in our Nation’s water bodies.
Progress Report
This report documents progress for Project Number 6060-13000-029-000D, which started in March 2022, and continues research from Project Number 6060-13000-026-000D, “Managing Water and Sediment Movement in Agricultural Watersheds.” Progress has been made on all three objectives and their subobjectives.
Under Objective 1 we made progress on testing managed aquifer recharge (MAR) technology utilizing riverbank filtration and groundwater transfer and injection (GTI) for the Mississippi River Valley Alluvial Aquifer (MRVAA). We conducted a 6-month continuous experiment and collected measurements of groundwater level and water quality; and collaborated with scientists, faculty, and graduate students at the National Center for Physical Acoustics, National Center for Computational Hydroscience and Engineering, U.S. Geological Survey (USGS), and University of Mississippi Department of Geology & Geological Engineering who are co-analyzing the data from the experiments. Near the riverbank filtration withdrawal site, we mapped river bathymetry and flow on a monthly basis that will be used to determine if pumping water near the river affects the hyporheic zone through which water flows to the aquifer. An alternative, more cost-effective MAR technology (relative to GTI), viz. vadose-zone recharge wells, was constructed to assess its effectiveness for groundwater recovery of the MRVAA. Databases comprising weather, surface and subsurface hydrology, aquifer lithology have been established to prepare for computer model development and testing to assess water resources management across the Mississippi Alluvial Plain, which overlies the MRVAA.
Under Objective 2 we completed the construction of a new flume, which will be used to study the erosion resistance of fine-grained soils found on farm land and used to construct levees and dams. Extensive tests were conducted to quantify the hydraulic forces acting on the flume bottom and develop relationships with bulk flow parameters. We continued to survey cross-section geometry of an irrigation reservoir levee to document ongoing erosion, and collected weather data to calculate wind-generated wave energy responsible for eroding the levee. We worked with land manager to plan for levee repairs and installation of protection measures after the lake was drained. Prototype-scale floating wave barriers as a protection measure were built and laboratory experiments focused on dimensioning of the mooring system for the wave barriers were completed. After establishing the methodology for automating pump control for our 100 ft-long laboratory channel, flow hydrographs with 1, 2, 3, 4, 5, and 6 hour durations were completed. Each dataset consists of real-time flow, slope, transport, and bed topography data throughout the experiments. Analysis of the dataset is ongoing at the time of this report. We made progress on successfully conducting sand erosion experiments in a laboratory channel with a new bi-modal size distribution of gravel on the bed of the channel. Also, two impact plates were successfully installed on the main channel of the Goodwin Creek Experimental Watershed, Mississippi. The impact plates have been operational since December, 2021 and have recorded data from particle impacts from more than 30 runoff events. A new bed load sampler was constructed and deployed on a refurbished sampling boom to allow the collection of physical samples of the bed load at the same time as impacts were being recorded. These samples will be used to calibrate the impacts for grain size of the impacting grains using amplitude and frequency information of the recorded signals. We made progress on further improving the USDA, ARS natural resources computer model AnnAGNPS by integration into the University of Mississippi WEB-based tool, Agricultural Integrated Management System. The integrated capabilities of AnnAGNPS to characterize and evaluate water, sheet and rill and gully erosion, combined with channel erosion models developed by the University of Mississippi within an on-line user interface will provide a critical management tool to evaluate the most efficient combination of conservation practices applied within watershed systems needed in conservation management planning to manage water and erosion. Ephemeral gully widening algorithms for AnnAGNPS and the USDA Conservation Planning Tool RUSLE2 have been improved by results from experiments on four different soils.
Under Objective 3 we continued to enhance our 40-year database comprising precipitation, runoff, sediment transport, land use and management, and channel morphology data at the Goodwin Creek Experimental Watershed to support the national Conservation Effects Assessment Project (CEAP) and Long Term Agroecosystem Research (LTAR) Network. Runoff samplers in aspirational and business-as-usual fields within the Lower Mississippi River Basin (LMRB) were established as well as annual biomass collection of cover crops and post-harvest was performed in support of LTAR. Progress has been made to develop a database of water and energy fluxes across the LMRB to examine the hydrologic processes across the critical zone of the Mississippi Alluvial Plain.
Accomplishments
1. Successfully conducted second long-term pumping/injection experiment. Reliance by agriculture on groundwater in the Mississippi River Valley alluvial aquifer (MRVAA) has resulted in long-term declines in water levels over much of the region. The main objective of the Groundwater Transfer and Injection Pilot (GTIP) project is to test the feasibility of withdrawing groundwater from near a large river and injecting the water into an area where the aquifer is depleted to be used later for irrigation. ARS researchers in Oxford, Mississippi, conducted a 6-month experiment, and collected groundwater samples monthly from 24 sampling points and groundwater levels continuously in 17 observation wells. Near the withdrawal site, the data indicate changes in water chemistry during riverbank filtration, showing a 10-fold decrease in suspended solids, whereas relatively small changes in water chemistry were observed near the injection wells. A groundwater mound, approximately 1.5 miles in diameter and 1–7 ft in height, formed near the injection site, while smaller impacts were observed near the extraction well where a groundwater depression formed approximately 1 mile in diameter and 1–5 ft in depth. These data will provide vital information needed for determining whether groundwater injection is a viable method for reversing declines in groundwater levels in the MRVAA. A wide variety of stakeholders have expressed keen interest in the GTIP project, including the Delta Council, Mississippi Department of Environmental Quality, Mississippi River Commission, Mississippi Soil and Water Conservation Commission, Natural Resources Conservation Service, U.S. Army Corps of Engineers, U.S. Geological Survey, and Yazoo Mississippi Delta Joint Water Management District.
2. Sustaining agricultural productivity, while preserving groundwater and surface ecosystems requires effective management of available water. The long-term sustainability of groundwater and terrestrial systems depends on understanding all the interactions of complex surface-groundwater flows at different scales of time and space. This also includes understanding the impacts of agricultural practices on water use. ARS researchers in Oxford, Mississippi, developed USDA modeling technology to support these efforts by combining the capability of a surface water model to characterize the impact of farming practices on groundwater levels with a subsurface flow model. The integrated technology was evaluated in the Upper Sunflower River watershed located in northwest Mississippi within the Lower Mississippi River Alluvial Plain. The integrated modeling technology was used to evaluate various irrigation strategies at varying time and space scales with observed values of streamflow at the outlet and well water levels throughout the watershed. Use of improved irrigation strategies demonstrated the sensitivity of streamflow and groundwater levels to irrigation strategies. Reduction of irrigation application rates by 20%-40% produced higher groundwater levels as estimated by the technology. This indicates the potential to positively impact the long-term sustainability of the aquifer with the adoption of more efficient irrigation strategies. The developed technology provides a management tool for action agencies, and is critical to understanding and evaluating the impact of agricultural practices, irrigation, and aquifer recharge strategies that are important to sustaining water resources in irrigated agricultural watersheds.
3. Novel time series analysis methods aid in evaluating land use and management impacts on watershed-scale sediment transport processes. Suspended sediment is listed as one of the leading pollutants that adversely impact the quality of U.S. rivers and water bodies. Effective management of suspended sediments at the watershed scale is difficult because of the spatial variability in sediment sources, land use and land management, and temporal lag effects caused by the event cycle of erosion and deposition. ARS researchers in Oxford, Mississippi, in collaboration with scientists from the University of British Columbia, Canada, used novel techniques (wavelet transform and coherence) to analyze a comprehensive 20-year record of land use, rainfall, stream flow, and suspended sediment concentration collected by the USDA, ARS, National Sedimentation Laboratory in the Goodwin Creek Experimental Watershed, Mississippi, at various spatial scales between 1982 and 2002. During the study period an overall decline in clay and silt suspended sediment load occurred across all time scales, which was primarily caused by land use change and in-channel stabilization. The spatiotemporal pattern of sand dynamics reflects both the state of channel stability and the availability of sand stored within the channel. The study shows that wavelet analysis can help evaluate the impact of land management practices on sediment transport processes, and therefore identify appropriate policies for future land use while mitigating environmental consequences.
