Project : USDA ARS

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Research Project: Science and Technologies for Improving Soil and Water Resources in Agricultural Watersheds

Location: Watershed Physical Processes Research

2025 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. 3.D. Assess long-term landscape agroecosystem sustainability using geophysical soil characterizations.

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
Progress was made on all three objectives and their subobjectives, all of which fall under National Program 211. Under Objective 1 we made progress in advancing knowledge on sustainability of groundwater dependent agroecosystems, including assessing the role of aquifer recharge in supporting a sustainable irrigation water source for farmers. Data collection and analysis continued for a managed aquifer recharge pilot project utilizing riverbank filtration and groundwater transfer and injection. Data included a novel application of geophysical measurements integrating electrical resistivity tomography and self-potential methods to identify groundwater movement during riverbank filtration (documented in the manuscript by Mamud et al., 2024). Findings indicate the design and implementation of the technology is fit for purpose, and stakeholders are using the pilot system as a template for expanding the program using the same overall approach. Near the riverbank filtration withdrawal site, we continued to map river bathymetry, bed material composition, and flow repeatedly to determine if pumping water near the river affects the hyporheic zone through which water flows to the aquifer. In collaboration with the University of Texas at Arlington, we finalized a machine-learning methodology and developed post-processing techniques to extract the drainage ditch systems in the Delta region of Mississippi, which was tested for the 12-digit Hydrologic Unit Code sub-watersheds Roundaway Bayou-Quiver River and Beaver Bayou-Mound Bayou. Also, in collaboration with the University of Texas at Arlington, we conducted hydraulic modeling analyses of the Roundaway Bayou-Quiver River sub-watershed to determine appropriate mesh-size for performing basin-scale hydrologic simulations of water resources in the Lower Mississippi River Basin using the Weather Research & Forecasting (WRF) and Advanced Terrestrial Simulator (ATS) computer models. Under Objective 2 we completed extensive tests to quantify the erosion-resistance of both cohesionless and cohesive soils. The critical shear stress for sand and very fine gravel material matched those found in the literature. We developed an improved post-processing method for the USDA jet erosion test (JET) to measure soil erosion resistance both in situ and in the laboratory. The new method accounts for both uncertainty of the measurement device and the eroded scour hole geometry. The measured erosion resistance presents significantly reduced noise and is now consistent between different sizes of the JET instrument. We continued to monitor weather, waves, and erosion at the Johnson Farm reservoir. Water levels were increased to approximately 75 cm, but the reservoir was not filled to capacity. The land manager plans to fill the reservoir for future rice plantings. We completed new analysis of an unsteady flow hydrograph data leading to a manuscript focused on comparing equilibrium and hydrograph flows at the same flow rate. It was found that the effects of hydrograph flows were stronger for shorter hydrographs, resulting in larger bedforms and higher transport rates for the hydrograph flows. The effect of repeated hydrographs was also greater for shorter hydrographs in the 1-3 hour range. We analyzed all incoming data from the impact plate system installed at measuring station 2 in the Goodwin Creek Experimental Watershed (GCEW). We submitted a manuscript describing the operation and calibration of the system and the first two years of data. We performed extensive analysis on data from ten pressure transducers installed last year at the slope-study reach immediately upstream of the measuring station. Preliminary findings show that maximum water surface slopes occurred at maximum flow rates, and counterclockwise hysteresis between water surface slope and flow rate for larger flow events (flow depths >1 m) was found. This indicates that, like unsteady flow flume experiments, bedforms that grew during rising flow rates are creating higher flow resistance for a given flow rate during falling flow rates. USDA soil and water conservation planning moved forward in two areas: RUSLE2 service and unmanned aerial systems (UAS) data collection. Three new manuscripts detail improved climate description for RUSLE2, including: methodology to reproduce climate database using 30-year window, in-depth discussion of the changes in weather patterns as the climate focus (30-year window) shifts in 5-year increments, and contiguous US soil loss evaluation using moving window (i.e., trends in soil loss across the U.S.). The UAS program collaborates with all projects (e.g., Long Term Agroecosystem Research (LTAR) network, Conservation Effects Assessment Project (CEAP)) across both research units at the National Sedimentation Laboratory. The Bank Stability and Toe Erosion Model (BSTEM) was enhanced by including boat and wind wave-generated bank erosion, which is critical for use of the model by the U.S. Army Corps of Engineers on navigable rivers and larger reservoirs. Under Objective 3 we made progress on adapting the USDA, ARS natural resources computer model AnnAGNPS for application within the University of Mississippi web-based tool, Agricultural Integrated Management System for use throughout the U.S. Testing was completed on several basin-scale simulations on the capability of using NASA developed climate data for the entire U.S., including evapotranspiration with good results. Characterizations were completed to identify areas of subsurface drainage to provide automated simulation capabilities for areas in the Midwest. This tool provides users with the capabilities to assess the impact of agricultural land management practices applied within any watershed system throughout the U.S. as an aid in the development of conservation management plans to manage water and erosion on farmlands. 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 CEAP and LTAR networks. We continued to collect samples of soil, biomass, as well as eddy covariance data as part of the common experiment across LTAR sites. We have three collaborative farmers, which allow us two comparisons of prevailing (PRV) practices versus two comparisons of alternative (ALT) field practices. Of the three farmers, one is owned and operated by a minority farmer in Mound Bayou, MS. A non-assistance cooperative agreement with Ohio State University resulted in gap filling and processing of backlogged eddy covariance data, which have been uploaded to the Ameriflux network. Coupling our UAS collection and analysis of LTAR and other laboratory projects has promoted continual growth and extension of UAS collection and data use.

Accomplishments
1. Conservation management planning for soil loss requires technology that represents the impact of climate on farm management practices and the implementation of conservation alternatives. Methods are needed to update the average annual rainfall erosivity for the entire continental US for use within the USDA Revised Universal Soil Loss Equation, Version 2 (RUSLE2) to assure consistency in erosion predictions for conservation planning. These methods will replace the laborious process of analyzing and processing data by hand to reproduce a smoothly and spatially varying average annual rainfall erosivity surface throughout the continental U.S. ARS researchers at Oxford, Mississippi, developed initial products based on information obtained from the U.S. National Oceanic and Atmospheric Administration (NOAA) stations. The data was processed following a strict protocol adhering to RUSLE2 science documentation that includes utilizing existing precipitation normals, distance to the U.S. coast, and continental elevation data to replicate the current RUSLE2 climate. The newly generated surfaces were compared to official surfaces and evaluated for smoothness. Results indicate agreement with RUSLE2 surfaces for absolute values but with slightly higher spatial and temporal smoothness. This approach provides the means for capturing long-term climatic variations impacting soil erosion in a consistent way and supports future updates to the RUSLE2 climate database. This also serves as a baseline for future enhancements in characterizing changing climatological drivers impacting soil erosion on farmlands.

2. Development of a novel groundwater model for flow induced by pumping and injection wells. Efficient use of water is needed to sustain irrigated croplands. Farmers and water managers often pump water from wells to irrigate agricultural fields to maximize cropland yields. Sustainable yields require that groundwater aquifers be replenished, with one option to return any available water back into the aquifers via injection wells for later use. Managing how to withdraw and replenish water in aquifers requires advanced modeling technology to accurately show how using these wells affect groundwater supplies. ARS researchers at Oxford, Mississipppi, adopted a simple and unique modeling approach to describe the complex system of groundwater flow that includes determining the impact of extracting and injecting water through wells on groundwater movement. This was accomplished by incorporating advanced geophysical techniques that measure complex underground systems into efficient numerical methods to describe extraction, injection, and water movement processes. The new model was tested with real-world data from a Mississippi Delta farming area where water was extracted from a plentiful groundwater source and transported nearly two miles for injection via wells into a depleted groundwater aquifer for eventual use as cropland irrigation water. The study showed that having detailed information from local farmers is key to making these models accurate. This work supports smarter farming practices and better water management, which benefits both agriculture and society.

3. A new jet erosion test processing technique for more reliable soil erosion-resistance values.. Soil erosion-resistance is critical information to improve stream function, protect land against floods and erosion, and safely store water in reservoirs. The jet erosion test or JET is a widely used method to derive the erosion-resistance parameters, but literature has indicated that their magnitude is sensitive to the size of the jet tester (original versus mini jet-test device) and estimation of the equilibrium depth of the scour hole eroded by the jet. ARS researchers at Oxford, Mississippi, developed a new JET post-processing method that produces more reliable estimates of erosion-resistance parameters by using a physically realistic scour hole evolution relation, directly fitting the erosion function relating erosion rate to applied shear stress, and accounting for measurement error and uncertainty. Analyses of 1,142 JETs show that mini and original jet-test devices measure equivalent erosion-resistance parameters with reduced variability in their magnitude, which will provide more confidence when using JET-derived erosion-resistance parameters in practice. These are critical information when conducting conservation management planning to improve the long-term sustainability of U.S. farms.

4. Managed aquifer recharge can help farmers irrigate with groundwater. Half the water used to irrigate farms in the United States comes from groundwater, which also is a key source of drinking water especially in rural areas. Pumping has led to declining aquifer water levels which can impair surface aquatic ecosystems, increase costs of pumping groundwater from greater depths, and cause a shortage of water to meet agricultural or drinking needs. ARS researchers at Oxford, Mississippi, conducted a Managed Aquifer Recharge pilot project in the intensively cultivated Delta region of Mississippi. Water is withdrawn from a well near the Tallahatchie River, where the river water is filtered naturally by moving through sands in the ground adjacent to the river, and subsequently injected using two wells into an area where aquifer water levels are lower. Results demonstrate that this technology can increase the amount of water in the aquifer under the unique hydrologic and geological conditions in the Delta. Stakeholders are using the pilot system as a template for expanding the program using the same overall approach.

5. Used steel plates with sensors to measure gravel moving through an agricultural stream channel. Gravel movement in streams and rivers needs to be measured to support the restoration of damaged streams, to help maintain healthy stream ecosystems, and for the design of in-stream structures. Measuring how much gravel moves through a stream is difficult because the amount of gravel changes quickly with time and location in the stream. Streams are often located in places that are hard to access, and flow events can occur during dangerous storm conditions, so methods are needed for automatically measuring gravel transport without personnel on site. In order to detect the movement of gravel particles, ARS researchers at Oxford, Mississippi, installed a steel impact plate system with special sensors that measure gravel particles striking the plates in a stream channel in the Goodwin Creek Experimental Watershed, Mississippi, USA. The impact plate system collected data for about three years with results showing that the approach can reliably measure gravel movement within this small stream system. The relationship between the flow rate and the amount of gravel moving down the stream was found to be different for rising flow rates and falling flow rates caused by rainfall in the watershed. The results can be used to guide other researchers, sediment transport modelers, and monitoring agencies who manage streams to make automatic measurements of gravel moving through stream systems.

6. Measured the effects of changing stream flows on the movement of sands in channels flowing through agricultural landscapes. Rivers and streams serve a vital role in routing water through agricultural watersheds, and prediction of the movement of sand and soil through the channels is an important component of managing them. However, there is a need to improve the scientific understanding of how rapidly changing flow rates, such as during intense rainfall events, affect the transport of sands in streams. ARS researchers at Oxford, Mississippi, used a laboratory channel to investigate the differences in sand transport and sand bed forms between changing flows and constant flows. Bed forms during rising flow rates were smaller than bedforms from the same constant flow rate. Bed forms were larger during falling flow rates than they were for constant flows of the same rate. The amount of difference depended on the length and magnitude of the flows. Longer flows had smaller differences, while higher flow rates had greater differences. These results increase the knowledge of the mechanisms that affect sediment transport and sand bed forms in streams with rapidly changing flows, which occur during runoff events caused by rainfall and dam-releases. The results will be used by researchers in the fields of sediment transport and river engineering, including those focused on modeling flow and sediment transport processes to improve the management of rivers and streams that flow through agricultural landscapes.

U.S. DEPARTMENT OF AGRICULTURE

Watershed Physical Processes Research: Oxford, MS