GAMA - Effects of Recharge on Groundwater Quality

California State Water Resources Control Board (State Water Board) staff are working to identify potential effects of recharge water on groundwater quality by reviewing and compiling data from over 35,000 wells and publishing it on a quarterly basis. This data is being used by staff to develop data tools that will assist members of the public with identifying and evaluating changing groundwater quality conditions. A preliminary study conducted by staff on the atmospheric rivers of 2023 has been compiled into a StoryMap.

State Water Board staff have developed a data visualization dashboard that allows users to compare groundwater quality results from approximately 35,000 wells with local monthly precipitation data and groundwater elevation measurements from DWR California Statewide Groundwater Elevation Monitoring (CASGEM) program, GeoTracker Depth-to-Water measurements, and USGS National Water Information System (NWIS) periodic groundwater level measurements. Various layers are available to be toggled on and off depending on the interest of the user.

Case studies based on available groundwater quality and precipitation data are being developed by State Water Board staff. Three locations in the Sacramento, San Joaquin, and Tulare County regions are being studied to better understand how extreme precipitation events can affect groundwater quality. Locations were chosen for the number of constituents sampled and the frequency of sampling before, during, and after precipitation events. Additional information such as soil type, land use, geologic history, groundwater depth, and well depth assist in developing these studies.

• The Department of Water Resources (DWR) is launching the DWR Flood-Managed Aquifer Recharge (MAR) Water Quality Sampling Pilot to investigate potential water quality impacts and benefits of flooding and MAR to groundwater. In collaboration with state, federal, and local partners, this Pilot will establish targeted water quality monitoring networks near known flooded areas and repeated managed aquifer recharge, primarily in the San Joaquin Valley. Groundwater water quality samples and groundwater level measurements will be collected on a quarterly or semiannual basis for approximately the next 4 years. Sampling is anticipated to begin in late Summer or early Fall 2025. Additional information will be posted here as available.
• Water quality permitting requirements for many Managed Aquifer Recharge (MAR) projects are unclear. The State Water Board and Regional Water Quality Control Boards (collectively, the Water Boards) are currently working to clarify existing permitting pathways for project proponents and identify MAR project types with unclear or inefficient requirements. The Water Boards may then propose and implement regulatory solutions that streamline water quality permitting for projects while continuing to protect beneficial use waters.