Groundwater Recharge in California

Project Lead: Benjamin Maki

California relies on groundwater as a critical source of irrigation and drinking water, supplying roughly 40-60% of statewide freshwater needs annually. However, years of over-pumping and drought have drastically depleted groundwater systems (aquifers) across the state. Managed aquifer recharge (MAR), a suite of methods which strategically reroutes excess surface water into underlying aquifers, is a key strategy being used to restore groundwater levels across the state. MAR projects have been widely applied by many groundwater sustainability agencies as part of their groundwater sustainability plans, required to meet sustainable groundwater management goals established by the Sustainable Groundwater Management Act (SGMA). However, changes to native geochemical conditions during recharge can result in the inadvertent mobilization of toxic naturally occurring contaminants, such as arsenic, uranium, chromium, and manganese. While groundwater recharge projects typically prioritize the quantity of water returned to aquifers, potential impacts to water quality are often overlooked, especially when multiple contaminants are considered. Enhanced field-scale groundwater quality monitoring is needed to better understand the potential long-term risks, or benefits, to water quality under different recharge methods. The information generated through these efforts can be utilized to better understand evolving groundwater conditions and inform system management decisions in real time. Current work funded through the Stanford Sustainability Accelerator, and in partnership with the Madera Irrigation District among other community partners, aims to establish a simple, functional multi-user focused toolkit to aid in effectively and safely scaling groundwater recharge efforts throughout the state. Importantly, this work focuses on both understanding community level concerns during local groundwater recharge projects, while simultaneous establishing effective monitoring approaches and designing simple, scalable, and effective management solutions to protect long-term groundwater quality.