Geology topics

Research about Mississippi Alluvial Plain

Source-linked reports with geographic coverage including Mississippi Alluvial Plain.

9 recordsLinked to original sources

USGS2026

Trends and seasonal patterns of nitrogen and phosphorus concentrations and loads in two Mississippi Alluvial Plain watersheds following nutrient reduction efforts during 2010–22

The Mississippi Alluvial Plain ecoregion in Mississippi was historically part of the largest continuous wetland in North America but was clearcut and converted to row crop agriculture beginning in the late 1800s. To reduce the effects of agriculture on surface waters in the Mississippi Alluvial Plain, nutrient reduction best management practices have been implemented throughout the region, particularly in two small watersheds: Harris Bayou watershed (174.04 square kilometers) and Porter Bayou watershed (267.15 square kilometers). Since 2009, the U.S. Geological Survey, in cooperation with the Mississippi Department of Environmental Quality, has collected water-quality samples monthly and during high-flow runoff events, at three locations within each watershed to monitor and assess nutrient trends following best management practice implementation. Here, we have analyzed long-term and seasonal trends in discharge, total nitrogen (TN), and total phosphorus (TP) concentrations and loads using a combination of quantile-Kendall analysis, quantile regression, generalized additive models, and weighted regression on time, discharge, and season. In Harris Bayou watershed, discharge values at a ~0.4–0.5 daily nonexceedance probability increased by 15 percent per year at the uppermost monitoring site. Additionally, TN concentrations decreased throughout the watershed over time, particularly in the spring and winter months. Reductions in TP were less apparent and only observed at one sampling location in Harris Bayou watershed. Nutrient concentrations in Porter Bayou watershed remained consistent over time and increased at one sampling location. However, despite discrepancies in concentration trends, flow-normalized TN and TP loads consistently decreased over time in both watersheds. At the mouth of both watersheds, peak TN and TP loads decreased between 37.7 and 56.9 percent. Collectively, these results provide evidence that best management practices may help reduce the effect of agricultural practices in the region, particularly in Harris Bayou watershed. Additionally, management efforts resulted in greater reductions in TN concentrations than in TP concentrations.

Mississippi↗

USGS2025

Hydraulic conductivity and transmissivity estimates from slug tests in wells within the Mississippi Alluvial Plain, Arkansas and Mississippi, 2020

During the spring and summer of 2020, the U.S. Geological Survey conducted single-well slug tests on selected observation wells within the Mississippi Alluvial Plain in Arkansas and Mississippi to estimate hydraulic conductivity and transmissivity values for the Mississippi River Valley alluvial and middle Claiborne aquifers. Well and aquifer data were collected from field measurements, well-construction reports, and published aquifer-thickness information. A total of 324 slug-in and slug-out tests were conducted on 48 wells by using mechanical slugs to displace the water column and submersible pressure transducers to record changes in water levels in the wells. Hydraulic conductivity of the aquifers in which the wells are screened was estimated by curve fitting the water-level-change data using aquifer test analysis software. Estimates of aquifer transmissivity were made by multiplying the estimated hydraulic conductivity value by the aquifer thickness at well locations. Mean hydraulic conductivity estimates for 44 observation wells screened in the Mississippi River Valley alluvial aquifer range from 3 to 401 feet per day, and mean transmissivity estimates range from 285 to 80,559 feet squared per day. Mean hydraulic conductivity estimates for four observation wells screened in units of the middle Claiborne aquifer range from 0.14 to 183 feet per day, and mean transmissivity estimates range from 55 to 67,913 feet squared per day. The results from these tests can be used to improve the understanding of water availability and groundwater migration, to refine groundwater models, and to ultimately provide stakeholders and decisionmakers better information for management of the groundwater resources within the Mississippi Alluvial Plain.

Arkansas, Mississippi↗

USGS2023

Estimating streambed hydraulic conductivity for selected streams in the Mississippi Alluvial Plain using continuous resistivity profiling methods—Delta region

Introduction The Mississippi Alluvial Plain is one of the most important agricultural regions in the United States, and crop productivity relies on groundwater irrigation from an aquifer system whose full capacity is unknown. Groundwater withdrawals from the Mississippi River Valley alluvial aquifer have resulted in substantial groundwater-level declines and reductions in base flow in streams within the Mississippi Alluvial Plain. These effects are limiting well production and threatening future water availability in the region. A comprehensive assessment of water availability in the Mississippi Alluvial Plain is critically important for making well-informed management decisions about sustainability, establishing best practices for water use, and predicting changes to water levels in the Mississippi Alluvial Plain over the next 50–100 years. The first step in the new regional modeling effort was to run the existing Mississippi Embayment Regional Aquifer Study (MERAS) model and perform data-worth and uncertainty analyses to prioritize data collection efforts to improve model forecasts. Parameter estimation indicated that streambed conductance was one of the variables that the model was most sensitive to, but little data were available to constrain those general estimates. From this characterization of the existing data, a map of the streams that the MERAS model was most sensitive to was created by the U.S. Geological Survey to guide the collection of 862 kilometers of waterborne resistivity surveys within the Delta region of Mississippi to characterize streambed lithology. This technique characterizes the streambed itself and the 15–30 meters below the streambed that control the exchange of water between the stream and the alluvial aquifer. These data can be used to map changes in the lithology of the streambed and identify areas of potential groundwater/surface-water exchange. Additionally, electrical and nuclear well logs from the study area were compared to facilitate the development of a petrophysical relation between the waterborne resistivity data and hydraulic conductivity. Resistivity values may then be used as a cost-effective way to approximate aquifer hydraulic conductivity distributions for use in regional groundwater models.

Arkansas, Louisiana, Mississippi↗

USGS2022

Mapped predictions of manganese and arsenic in an alluvial aquifer using boosted regression trees

Manganese (Mn) concentrations and the probability of arsenic (As) exceeding the drinking-water standard of 10 μg/L were predicted in the Mississippi River Valley alluvial aquifer (MRVA) using boosted regression trees (BRT). BRT, a type of ensemble-tree machine-learning model, were created using predictor variables that affect Mn and As distribution in groundwater. These variables included iron (Fe) concentrations and specific conductance predicted from previously developed BRT models, groundwater flux and age estimates from MODFLOW, and hydrologic characteristics. The models also included results from the first airborne geophysical survey conducted in the United States to target an entire aquifer system. Predictions of high Mn and As occurred where Fe was high. Predicted high Mn concentrations were correlated with fraction of young groundwater (less than 65 years) computed from MODFLOW results. High probabilities of As exceedance were predicted where groundwater was relatively old and airborne electromagnetic resistivity was high, typically proximal to streams. Two-variable partial-dependence plots and sensitivity analysis were used to provide insight into the factors controlling Mn and As distribution in groundwater. The maps of predicted Mn concentrations and As exceedance probabilities can be used to identify areas where these constituents may be high, and that could be targeted for further study. This paper shows that incorporation of a selected set of process-informed data, such as MODFLOW results and airborne geophysics, into a machine-learning model improves model interpretability. Incorporation of process-rich information into machine-learning models will likely be useful for addressing a wide range of problems of interest to groundwater hydrologists.

Arkansas, Louisiana, Mississippi, Tennessee↗

USGS2021

Aquaculture and Irrigation Water-Use Model (AIWUM) version 1.0—An agricultural water-use model developed for the Mississippi Alluvial Plain, 1999–2017

Water use is a critical and often uncertain component of quantifying any water budget and securing reliable and sustainable water supplies. Recent water-level declines in the Mississippi Alluvial Plain (MAP), especially in the central part of the Mississippi Delta, pose a threat to water sustainability. Aquaculture and Irrigation Water-Use Model (AIWUM) 1.0, one of the first national agricultural water-use models that provides water use at the scale of most groundwater models, was developed and compared to other reported and estimated aquaculture and irrigation water-use values within the MAP study area for 1999 through 2017 to improve water-use estimates needed as input to a hydrologic decision-support system in the MAP. Results indicate annual total water-use estimates from 1999 through 2017 ranged from about 5 to 13 billion gallons per day and, on average, a majority of the water use was applied to rice (about 51 percent), followed by soybeans (about 26 percent), and less than (<) 10 percent each was applied to aquaculture, corn, cotton, and other crops. Comparisons indicated that annual total water-use estimates from AIWUM 1.0 were smaller than or comparable to all other sources of water-use data. Although there is disagreement at the monthly timescale in estimates in the Mississippi Delta within each part of the growing season, the annual total water use is comparable between AIWUM 1.0 and the Mississippi Embayment Regional Aquifer Study groundwater model 2.1. Estimates from AIWUM 1.0 could be used in models at all scales (for example, local, regional, national) and could provide a nationally consistent methodology in estimating water use driven by regional crop-specific withdrawal rates.

Arkansas, Illinois, Kentucky, Louisiana, Mississip↗

USGS2020

Farmer behavior under groundwater management scenarios: Implications for groundwater conservation in the Mississippi Alluvial Plain

Concern about sustained availability of fresh groundwater for agricultural use in the Mississippi Alluvial Plain (MAP) mounts as groundwater levels decline. We evaluate elasticities of demand for groundwater and other agricultural inputs, as well as overall and output specific economies of scale for four major irrigated commodities (rice, corn, soybeans, and cotton) in the MAP region. Additionally, we investigate impacts of two groundwater management policy scenarios, including increasing pumping cost and groundwater use restrictions, on irrigation behavior. The results show price elasticity of demand for groundwater to be -0.13, indicating that it is inelastic, and an increasing cost of pumping will not significantly decrease relative demand for groundwater in the region. Even with policy scenarios that either increase the costs of pumping significantly or restrict groundwater use in the region, groundwater demand still appears to be inelastic. We also document significant overall economies of scale in the region. Our findings have implications for potential policy options aimed at reducing groundwater use. Efficient management practices are important to increase aquifer recharge, and at the same time, incorporation of human behavior via economic analysis will improve projections of groundwater availability in the MAP region.

Missouri, Tennessee, Arkansas, Louisiana, Mississi↗

USGS2019

The use of national datasets to produce an average annual water budget for the Mississippi Alluvial Plain, 2000–13

Overview Water is a critically important resource for the Mississippi Alluvial Plain (MAP) region, supporting a multibillion-dollar agricultural industry. There are concerns that continued withdrawals of groundwater for irrigation may decrease future water supplies. The U.S. Geological Survey has a history of conducting research in the MAP region and recently began an effort to integrate multiple monitoring analyses and modeling to characterize and project water availability for the region. Here, we utilize the data and results from existing national-scale datasets and refine them to create long-term steady state annual water budgets at a regional scale (the MAP) from 2000 to 2013. The water budget is described and mapped as the distribution of available water into three components: (1) evapotranspiration (65 percent); (2) quickflow runoff to streams (27 percent); and (3) groundwater recharge (8 percent). We also present a comparison of long-term recharge rates with groundwater extraction rates. These results will be useful as a starting point for the water budget and evaluations of future water availability in the MAP.

Arkansas, Kentucky, Louisiana, Mississippi, Missou↗

USGS2019

The Mississippi Alluvial Plain aquifers—An engine for economic activity

U.S. Geological Survey science supports groundwater resource management in the Mississippi Alluvial Plain region. The USGS Science and Decisions Center is working with the Water Availability and Use Science Program to integrate economics into a sophisticated model of groundwater in the region. The model will quantify the status of the groundwater system and help researchers, stakeholders, and decision-makers understand and manage groundwater resources. Including economics in the model will let users consider the influence of groundwater levels on regional economics and the effects of economic factors on the demand for groundwater.

Mississippi Alluvial Plain↗

USGS1973

Hydrology of the Bayou Bartholomew alluvial aquifer-stream system, Arkansas

The study area comprises about 3,200 square miles of the Mississippi Alluvial Plain in southeast Arkansas. About 90 percent of the area drains south to the Ouachita River in Louisiana. The alluvial aquifer and the streams are hydraulically connected and are studied as an aquifer-stream system. Bayou Bartholomew is a principal stream of the system. The aquifer is underlain by confining strata of the Jackson Group and Cockfield Formation. The mean annual surface-water yield of the area that drains to the Ouachita River basin is nearly 2 million acre-feet. Flood-control projects have significantly reduced flooding in the area. Basin boundaries and low-flow characteristics of streams have been altered as a result of the flood-control projects and streamflow diversion for irrigation. The direction of ground-water flow generally is southward. Bayou Bartholomew functions mostly as a drain for ground-water flow from the west and as a recharge source to the aquifer east of the bayou. As a result of navigation pools, the Arkansas River is mostly a steady-recharge source to the aquifer. Pumpage from the aquifer and streams increased from about 20,000 acre-feet in 1941 to 237,000 acre-feet in 1970. Estimates of flow, derived from analog analysis but lacking field verification, indicate that recharge to the aquifer in 1970 was about 161,000 acre-feet. About 70 percent of the recharge was by capture from streams as a result of ground-water pumpage. Discharge from the aquifer was about 233,000 acre-feet. About 80 percent of the discharge was through wells. Stream diversion in 1970 from capture and open channel, excluding capture from the Arkansas and Mississippi Rivers, was about 110,000 acre-feet. Return flow to streams from rice irrigation and fishponds was about 60,000 acre-feet. The chemical quality of streamflows is excellent for irrigation. Water from the aquifer generally ranges from permissible to excellent for irrigation. The use of water from the aquifer in the flood-plain area, exclusive of irrigation, is severely limited unless it is treated to remove the iron and reduce the hardness.

Arkansas↗