Uncovering the gaps in managed aquifer recharge for sustainable groundwater management: A focus on hillslopes and mountains

Authors: Meles, Menberu; Bradford, Scott; CASILLAS-TRASVINA, JESUS - University Of California, Davis; CHEN, LIN - University Of California, Riverside; Osterman, Gordon; Levers, Lucia; HATCH, TYLER - Intera, Inc; AJAMI, HOORI - University Of California, Riverside; Crompton, Octavia; KISEKKA, ISAYA - University Of California, Davis

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2024
Publication Date: 7/4/2024
Citation: Meles, M.B., Bradford, S.A., Casillas-Trasvina, J.A., Chen, L., Osterman, G.K., Levers, L.R., Hatch, T., Ajami, H., Crompton, O.V., Kisekka, I. 2024. Uncovering the gaps in managed aquifer recharge for sustainable groundwater management: A focus on hillslopes and mountains. Critical Reviews in Environmental Science Technology. 639. https://doi.org/10.1016/j.jhydrol.2024.131615.
DOI: https://doi.org/10.1016/j.jhydrol.2024.131615

Interpretive Summary: Managed Aquifer Recharge (MAR) techniques have been developed and implemented to assist groundwater replenishment. However, many of these methods are limited by scale, timing, and other challenges related to unknowns that affect water quality. This paper explores missing components in existing groundwater recovery activities that could enhance the replenishment of severely depleted groundwater. We highlighted the hydrological potential of hillslopes and mountains with roadside collection and conveyance systems in MAR as an underutilized recharge water source and site. These include modifying landscape slopes using biological and physical structures (built and geological) that slow water flow and increase recharge. These strategies provide numerous advantages over valley floors, such as enhancing connectivity and faster recharge rates to deep aquifers, and better source water quality with fewer legacy contaminants. Using existing roadside channel systems that usually collect large amounts of runoff from the mountain fronts may enhance groundwater recharge.

Technical Abstract: Managed Aquifer Recharge (MAR) is a promising approach to enhance water supply resilience, but it faces significant challenges, such as limited space and time for recharge activities, as well as uncertain bio-geophysical processes, and complex subsurface flow and heterogeneity. In this review, we assess the viability of hydrology-based approaches to enhance groundwater replenishment and identify missing components in existing groundwater recovery activities. We discuss expanding recharge opportunities to under-utilized sources and locations such as hillslopes and mountain systems. Additionally, we explore the possibilities of using existing road infrastructure to capture runoff and convey it to secondary porosity (lineaments) in the mountain fronts. Conventional MAR approaches are usually implemented on valley floors where restrictive clay layers can impede recharge to deep aquifers, and the presence of legacy contaminants in the root or vadose zones can degrade water quality. Hillslope and mountain recharge strategies offer multiple potential benefits over valley floors when there is improved connectivity and faster recharge to deep aquifers, shallower vadose zones, coarser textured deposits, and better surface water quality. Studies show that hillslope recharge accounts for 15-50% of the recharge to valley floors. To further facilitate the effective expansion of groundwater recharge, we propose landscape modifications encompassing slope correction and implementing biological and structural techniques to repurpose roadside channel systems to slow down and/or store flow in hillslopes. These systems can facilitate groundwater recharge and ultimately contribute to sustainable groundwater management. Innovative scientific analyses can help us understand the impacts of MAR on water quality and quantity, uncover the limitations and strengths of recharge in specific locations, and identify the most effective systems. Addressing these gaps will help us achieve a more resilient and sustainable groundwater future.