RAPID: Managed Groundwater Recharge (MAR) in a year of exceptional precipitation: Evaluating the impact of dry-well versus on-farm recharge on water quality

Groundwater is a vital resource that provides drinking water to 2.5 billion people on earth and accounts for about 43% of the water used for irrigation. Many regions have experienced significant depletion in groundwater resources over the last decades. Increased groundwater depletion has motivated the intentional recharge of groundwater aquifers with excess surface water. Intentional groundwater recharge, also called managed aquifer recharge (MAR) has many benefits. It can increase groundwater storage, decrease land subsidence, mitigate flood risk, starve-off sea water intrusion, help regulate streamflow and stream temperature during dry seasons, and improve overall water security. This research will investigate the difference in groundwater quality between two MAR strategies that are used to introduce surface floodwaters into the groundwater system at two side-by-site locations in Central Valley California. Their findings will future implementation of intentional groundwater recharge strategies that improve groundwater quality for communities. Following the exceptionally wet year in California that recorded over 300% of its normal precipitation in snowpack and rainfall, resulting in widespread flooding, researchers will study the effect of using the floodwater to recharge aquifers, at two sites undergoing two different MAR strategies, on the quality of groundwater. The MAR strategies are drywells injection and surface flooding of farm fields. The researchers will investigate the occurrence, distribution, and changes in the concentrations of anthropogenic and geogenic contaminants such as nitrate, arsenic, uranium, chromium, other pesticides, and indicators of coliform bacteria. Investigators will quantify the release of contaminants to groundwater from each recharge strategy and assess the links between contaminant mobilization processes to hydrogeochemical conditions that affect the mobilization. The findings from this research will improve understanding of the effect of different managed aquifer recharge strategies and inform the future development of treatment and abatement options during the recharge process for future water management practices. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.