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

2023 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
Under Objective 1 we completed operational testing for a pilot project assessing the feasibility of managed aquifer recharge (MAR) technology utilizing riverbank filtration and groundwater transfer and injection (GTI) for the Mississippi River Valley Alluvial Aquifer (MRVAA). A 204-day experiment involving continuous injection totaling 575 acre-feet of water was completed. Groundwater level and water quality data collected during this experiment and a prior 89-day experiment were analyzed and results demonstrate the technical feasibility of increasing the volume of groundwater in the MRVAA in the Mississippi Delta using the tested technology. Results have also shown the need for increasing the capacity of the system so that more filtered river water can be extracted for recharging the aquifer. Near the riverbank filtration withdrawal site, we mapped river bathymetry and flow on a quarterly basis that will be used to determine if pumping water near the river affects the hyporheic zone through which water flows to the aquifer. In addition, an extended, 20-mile reach was mapped and bed-material samples collected, which data will be used to test approaches that estimate channel properties across the Mississippi Delta. In collaboration with the University of Texas at Arlington, a machine-learning methodology was developed to extract the drainage ditch systems, which was tested for the 12-digit Hydrologic Unit Code (HUC12) sub-watersheds Roundaway Bayou and Beaver Bayou-Mound Bayou. This data set is needed to examine the interactions between surface water and groundwater. Under Objective 2 we continued conducting extensive tests to quantify the hydraulic forces acting on the bottom of the new soil erosion flume, which will be used to study the erosion resistance of fine-grained soils found on farmland and used to construct levees and dams. These tests have resulted in a modification of the geometry of the sluice gate for flow improvement. We continued monitoring weather and water conditions near the Johnson irrigation reservoir where we are preparing to repair a section of the levee on the reservoir that was cut by the landowner. After completion of the levee repair, we can deploy prototype-scale floating wave barriers to reduce levee erosion. We completed an extensive analysis of a first series of six unsteady flow hydrographs from 1 to 6 hours in length. Major findings include the effectiveness of the Engelund-Hansen method, a predictive equation for total sediment load, when used with detailed water surface slope measurements for predicting changing sediment loads throughout the hydrographs. A second series of six flume experiments wherein multiple unsteady hydrographs were applied to a sand bed were begun. Hydrographs with lengths between 1 to 6 hours are being repeated three times while comprehensive measurements of hydraulic conditions are collected so that the effects of the hydrographs can be quantified. Experiments dealing with sand erosion in gravel bed channels were completed during the past year. Data are currently being analyzed and preparation of a manuscript is in progress. The study of the transport of bed load on Goodwin Creek using impact plates is ongoing. Data on bed load has been collected from almost all sediment transporting events over the past year and a half. Calibration samples were collected from two runoff events, and a calibration equation was developed by matching the distributions of the collected grain masses with the distributions of the magnitudes of the recorded impacts. Preliminary analyses of the bed load data from 50 runoff events are in progress. Comparative analyses showed RUSLE2 is a stable and consistent performance application for USDA-Natural Resource Conservation Service (NRCS) soil loss prediction and conservation management. New RUSLE2 research components were developed to move RUSLE2 from the desktop into the cloud. We introduced new methodology to RUSLE2 to improve predictions of runoff from agricultural systems under varying climate conditions, which is currently under calibration and validation using data from the United States Midwest region. 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 to evaluate the impact of land management practices applied within watershed systems needed in conservation management planning. 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 (GCEW) to support the national Conservation Effects Assessment Project (CEAP) and Long Term Agroecosystem Research (LTAR) Network. A new hillslope hydrologic monitoring site was established at GCEW, comprising a hillside pasture adjoining a flat riparian row-crop field. The site will enable assessment of conservation practices that can reduce the volume and velocity of runoff while increasing recharge—such as contour grading of berms/swales, check dams, and on-farm reservoirs—and determine the effects on groundwater-surface water interactions. An initial subsurface characterization was completed using electrical resistivity tomography (ERT) geophysical data. The ERT data along with shallow soil core samples show that the aquifer is relatively thin (<10 m) near the creek and thick (>30 m) under the pasture. Elevation and multi-spectral data were collected by unmanned aerial system (UAS) for the various LTAR sites in the Mississippi Delta. Dashboards were developed to automate the ingestion of climate, water and energy fluxes across the Lower Mississippi River Basin into basin-scale regional climate and hydrologic computer models. These models are used to examine the hydrologic processes across the critical zone of the Mississippi Alluvial Plain.

Accomplishments
1. Design of conservation plans can improve water quality in agricultural watersheds and downstream waterways. A challenge for conservationists is managing limited resources, while minimizing agricultural production loss and reducing sediment loads. ARS researchers in Oxford, Mississippi, integrated GIS-based analyses with hydrological modeling at watershed scales, which provided additional capabilities to quantify the effect of conservation practices to sediment loads by spatially characterizing different types of conservation practices and scenarios and their relative impact on sediment reduction. The proposed methodology was applied to a west Tennessee watershed that has been identified as impaired due to high loads of suspended sediments from agricultural sources. This investigation demonstrated the need for inclusion of more variables in the decision-making process, such as costs of implementation, costs of maintenance, and potential loss of income from a reduced production area. The inclusion of machine learning algorithms could also aid in the task of selecting and simulating a combination of different types of practices by controlling their associated model parameters, and their location in the watershed. This technology could lead to the development of hybrid customized solutions for impaired watersheds utilized by conservationists to target the most effective practices at the optimal locations for sediment load reductions throughout the landscape.

2. Global analysis of cover management and support practice factors that control soil erosion and conservation planning. The effects of land management and conservation practices on soil loss are represented by the factors C and P for the conservation planning tool Revised Universal Soil Loss Equation (RUSLE). Globally, very limited field studies have been conducted to quantify C and P values across a broad range of climate, soils, crops, management and conservation practices. ARS researchers in Oxford, Mississippi, in collaboration with researchers from Belgium, Ethiopia, Italy, Japan, and Switzerland, reviewed values of the C and P factors published in 255 peer-reviewed journal papers. The published values varied widely across climatic zones, land use or cover types, and support practices. The C-factor was highest in areas with low rainfall and in cropland, whereas the P-factor was largest at high elevation and in areas with a humid climate and high rainfall. Because RUSLE is an important tool to assess land degradation globally, the compiled datasets of C- and P-factor values can be used by researchers and policymakers to support large-scale planning and evaluation of integrated catchment management interventions. This is particularly beneficial for areas where it is difficult to obtain empirical information about the impact of land or cover type changes and support practices.

3. New managed aquifer recharge technology utilizing riverbank filtration and groundwater transfer and injection demonstrated in the Mississippi Delta. The Mississippi River Valley Alluvial Aquifer (MRVAA) provides over 90% of the irrigation water used in the intensively cultivated Delta region of northwestern Mississippi, with more than 20,000 irrigation wells supplying water to 1.8 million acres of cropland. Reliance on groundwater has resulted in long-term declines in MRVAA water levels over much of the region. ARS researchers in Oxford, Mississippi, have been operating the Groundwater Transfer and Injection Pilot (GTIP) project to test the feasibility of pumping groundwater from near a large river and injecting the water into an area where the aquifer is depleted to be used later for irrigation. Two test injections with durations of three and six months demonstrated the technical feasibility of combining riverbank filtration with groundwater transfer and injection to increase the amount of groundwater in the Delta. However, they also illustrated several challenges for potential implementation of managed aquifer recharge technology in the region. Stakeholders have requested input from ARS on expansion of the system beyond the pilot scale, including potential modifications of or alternatives to current extraction and injection technologies.

4. RUSLE2 climate update incorporates climate records from 1971-2022. The climate files used with the current Revised Universal Soil Loss Equation version 2 (RUSLE2) conservation management planning tool were generated between 1971-1999. ARS researchers in Oxford, Mississippi, collaborated with Middle Tennessee State University researchers to download all National Oceanic and Atmospheric Administration-National Climate Data Center (NCDC) records for the 1971-2022 period. The states and territories served by the Natural Resources Conservation Service were gridded and pseudo stations were populated with closest NCDC station data, gaps were filled with other neighboring stations. Events larger than the 50-year planning period were eliminated, which and events with less than (<) 13 mm precipitation were also eliminated, which is essential to fairness to the farmer. The most recent 25-year records were used to generate the county climate records for RUSLE2 conservation planning. Climate updates are essential to conservation management, incorporating effects of changing weather patterns (rainfall intensity and duration and wet and dry periods) to balance soil conservation and profitability of U.S. farms.

5. Quantifying the effects of rapidly changing flow rates on sand transport and bed topography. Streams and rivers often have flow rates that change with time, which affects the configuration of the channel bed and the transport of sediments. These changing conditions make it more difficult to predict the amount of sediment transported through the channel, and research is needed to improve these predictive abilities. In a laboratory flume, ARS researchers in Oxford, Mississippi, created periods of increased flow rate that varied from 1-6 hours and mimicked flows caused by runoff events in streams. It was found that the Engelund-Hansen relationship could reasonably predict total sediment load when used with detailed water surface slope measurements throughout the hydrographs. The amount of sand transported by the flow increased as the length of time increased, even though the maximum flow rate was the same. The height of bedforms increased with hydrograph period, but the length stayed approximately the same for hydrographs greater than 2 hours long. These results will help to understand and predict the effect of runoff events on sediment transport in streams where the flow rate changes rapidly, as is often the case on small streams near agricultural fields.

6. Developed computer algorithms for processing gravel impact measurements. Gravel transport in streams is difficult to measure and varies rapidly in both space and time, making continuous monitoring necessary for accurate measurements. ARS researchers in Oxford, Mississippi, installed a system in Goodwin Creek, Mississippi, to record gravel impacts on a steel plate mounted on the bottom of the channel. The data from the plate system requires analysis before they can be converted into gravel transport rates. Computer algorithms were written and then refined over time for the detection of gravel impacts and for establishing a calibration relationship based on physical samples collected concomitantly with impact plate data. This effort has resulted in continuous records of gravel transported over the plates for over one year. The data are being used to examine relationships between flow rate and gravel movement and detect patterns in gravel transport over time. This information is leading to better understanding of how gravel transport in a stream is affected by previous flows, local channel conditions, and by changing rainfall and runoff patterns.

U.S. DEPARTMENT OF AGRICULTURE

Watershed Physical Processes Research: Oxford, MS