"Managed Aquifer Recharge Utilizing Riverbank Filtration and Groundwater Transfer and Injection: A Potential Technology for Sustainable Groundwater-Irrigated Agroecosystems"

Andrew M. O'Reilly (Andy) | Research Hydrologist, National Sedimentation Laboratory, USDA, Agricultural Research Service

Long-term declines in groundwater levels in the Mississippi River Valley alluvial aquifer (MRVAA) threaten the sustainability of agroecosystems in the Lower Mississippi River basin dependent on the aquifer for irrigation water. To assess the potential for managed aquifer recharge to support irrigated agriculture in this region, the U.S. Department of Agriculture Agricultural Research Service, in partnership with local stakeholders and the U.S. Army Corps of Engineers, is conducting the Groundwater Transfer and Injection Pilot (GTIP) project near Greenwood, Mississippi. The system consists of one extraction well, a 1.8-mile pipeline, and two injection wells, with a design capacity of 1,500 gpm. Groundwater is filtered by passing through sands adjacent to the Tallahatchie River and subsequently is extracted, transferred, and then injected into a depleted section the MRVAA. Operational tests of 3- and 6-month duration have been completed, injecting a total of 550 and 575 ac-ft, respectively. I will summarize objectives and construction of the GTIP project and, based on some expected and unexpected experiences from the pilot testing, describe preliminary results and lessons learned.

"Innovative Drywell Designs and Applications for Enhanced Managed Aquifer Recharge"

Scott A. Bradford, Ph.D. | Research Leader, USDA, ARS SAWS Unit

Managed Aquifer Recharge (MAR) is an important tool to mitigate the adverse effects of drought, floods, and changing climatic conditions. Flooding of agricultural fields (Ag-MAR) has being proposed to sustainably manage groundwater supplies, but potential limitations include low permeability soils, leaching of contaminants in the root zone, evaporation losses, and adverse impacts on crop health. This presentation highlights innovative designs and applications of drywells to overcome these limitations. A drywell is a infiltration system that has a small footprint at the land surface that is installed and releases water at varying depths into the vadose (unsaturated) zone. Field data and numerical simulations reveal that infiltration and recharge from a drywell can occur over a much larger area (e.g., 70 m diameter) than its surface footprint (e.g., <1.2 m diameter). The lowest levelized costs associated with recharging a given water volume occurred for smaller and deeper drywells that recharged water over a shorter timeframe.  Potential novel MAR applications of small diameter and deep drywells, including (i) repurposing of existing dried irrigation supply and domestic wells; and (ii) inclusion of drywells into existing irrigation canal systems. Widespread application of these MAR approaches is predicted to relatively rapidly recharge tremendous volumes of floodwater. Site-specific technical and regulatory hurdles still need to be addressed, and pilot-scale studies are therefore needed before large-scale implementation.

To view presenter bios, presentation descriptions, and to register, visit the GWPC Web site.