Feasibility of infiltration galleries for managed aquifer recharge in the mississippi river valley alluvial aquifer of northeast Arkansas

Authors: Godwin, Ian; Reba, Michele; LESLIE, DEBORAH - University Of Memphis; ADAMS, RYAN - Us Geological Survey (USGS); RIGBY, J.R. - Us Geological Survey (USGS)

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2022
Publication Date: 2/9/2022
Citation: Godwin, I.A., Reba, M.L., Leslie, D., Adams, R., Rigby, J. 2022. Feasibility of infiltration galleries for managed aquifer recharge in the mississippi river valley alluvial aquifer of northeast Arkansas. Agricultural Water Management. 264:107531. https://doi.org/10.1016/j.agwat.2022.107531.
DOI: https://doi.org/10.1016/j.agwat.2022.107531

Interpretive Summary: The water that supports the agricultural economy of eastern Arkansas comes from a highly productive, yet relatively thin groundwater aquifer. This aquifer has been over-pumped for decades, leading to declines in groundwater storage and availability. Efforts to transition to surface water use and improve irrigation efficiency are growing in the areas of greatest declines. These efforts could be supported by increasing the amount of water returning to the aquifer through a process called managed aquifer recharge (MAR). Mapping, subsurface measurements, and sediment analyses were conducted in this study to locate areas most appropriate for MAR in the Cache River region of northeast Arkansas. More than a third of the study area was found to have surface conditions favorable for MAR using infiltration galleries, which are gravel-filled trenches designed to move surface water into the aquifer. Furthermore, hydraulic properties and sediment geochemistry of the upper aquifer appear to be adequate for effectively moving water to the subsurface with limited adverse effects to water quality. Initial results from this study will be used to plan pilot tests of MAR in the region to aid in groundwater conservation. Water managers and producers are interested in understanding where MAR might be effective to help alleviate groundwater decline.

Technical Abstract: Over-pumping of the Mississippi River Valley Alluvial Aquifer for irrigation supply has led to severe drawdown. The Cache River Critical Groundwater Area (CRCGA) of northeast Arkansas has experienced declines of over 30 m and is threatened by additional aquifer depletion in the near future. In addition to adopting surface-water storage and water-efficient farming methods for groundwater conservation, farm-scale managed aquifer recharge (MAR) with infiltration galleries (IG) may be a useful tool for reducing declines. Low-permeability surface deposits, which greatly limit natural recharge across the region, also control the placement of potential MAR systems. It is therefore critical to understand the variability of these deposits, as well as underlying aquifer properties, to best plan the placement, design, and operation of such systems. This study aimed to characterize these conditions to assess the feasibility of infiltration galleries in the central CRCGA. Available well logs were used to map the approximate thickness of surface deposits and identify areas with the thinnest confining unit. Guided by this mapping effort, geophysical and soil surveys were conducted at selected sites. Approximately 37% of the study area, including 28 existing reservoirs that could act as recharge water sources, was identified as having less than 5 m of confining material at the surface. The upper aquifer is fine silty-sand with estimated hydraulic conductivities of 0.20 to 2.79 m d-1. These initial survey results are promising for the implementation of farm-scale IG in the study region and will be used in the construction of a forthcoming pilot IG project.