Development of a Pilot-Scale Managed Aquifer Recharge Facility that Combines Riverbank Filtration, Groundwater Transfer, and Injection in an Intensively Cultivated Agroecosystem

Highlights Groundwater depletion of the Mississippi River Valley alluvial aquifer threatens agroecosystem sustainability. Direct injection is a high-capacity managed aquifer recharge (MAR) technology to potentially reverse depletion. Leverages excess surface water to support existing irrigation systems with a small infrastructure footprint. MAR implementation example for similar efforts where groundwater depletion impacts farming and water resources. Abstract. Alluvial basins commonly contain both fertile soils and shallow high-yielding aquifers, forming highly productive regions for irrigated agriculture worldwide. The Mississippi Alluvial Plain in the Lower Mississippi River Basin of the United States is one such region, where irrigation demands during the growing season have contributed to long-term depletion of the Mississippi River Valley alluvial aquifer (MRVAA), adversely impacting farming operations in some areas. Managed aquifer recharge (MAR) is a technology for leveraging excess surface water resources by storing water in the subsurface for subsequent beneficial use. A pilot-scale MAR facility that combines riverbank filtration, groundwater transfer, and injection was conceived and built to address sustainability concerns for groundwater irrigation in the Delta region of northwestern Mississippi, USA. This article establishes the need for the facility, describes the steps that led to the decision to pursue it, details the process of securing funding and permissions, and describes the construction and successful shakedown assessments of the facility. During testing of the facility at a flow rate of 94.6 L/s (1,500 gal/min) for 24 h, water level increases of up to 1.48 m (4.85 ft) were measured in the MRVAA at the injection site, whereas water level impacts in the MRVAA at the riverbank filtration extraction site were relatively small, with drawdowns up to 0.91 m (2.99 ft). Pre-operational water sampling results indicate groundwater in the MRVAA at both the extraction and injection sites is anoxic (dissolved oxygen 0.06 to 0.11 mg/L) and elevated iron (1.75 to 31.2 mg/L) and manganese (0.253 to 0.979 mg/L) concentrations indicate reducing geochemical conditions, suggesting chemically compatible conditions for the mixing of recharge water obtained from the extraction well and ambient groundwater at the injection site. Results provide a foundation to potentially expand MAR at a larger scale in the MRVAA in the Delta and an example to pursue similar MAR technology in other intensively cultivated alluvial basins where groundwater level declines are impacting farming and water resources.