Maximizing Groundwater Sustainablity in a Highly-Urbanized Southern California Groundwater Basin

In Southern California, increasing demand for water is forcing water agencies to look harder at the integration of surface and groundwater resources. In recent years an extended drought period has resulted in declining groundwater levels in the Verdugo Groundwater Basin in Southern California and reduced water supply reliability. Crescenta Valley Water District (CVWD) conducted a detailed Feasibility Study to evaluate the potential for artificially recharging the Basin to increase the amount of groundwater in storage. The results of the study will help improve the reliability of the water supply for thousands of residents in the area. The feasibility study received special notice from the California Department of Water Resources as an exemplary project. Surface water flows, including stormwater, were identified as a viable water source for recharge. Potential recharge locations, required recharge facilities, and administrative and regulatory opportunities and constraints were considered in the development of specific alternatives. Alternatives were then ranked and a conceptual design for the preferred alternative was prepared. The preferred alternative is for recharge of storm runoff using subsurface infiltration galleries installed beneath a local park. Key challenges to recharge include wide variations in surface water flow rates following storms (large peak flows would be difficult to capture), high turbidity levels that can clog recharge facilities, and varying water quality, as surface runoff from urban areas may contain oils, metals, and fertilizers. These challenges were considered and addressed in the development of the preferred recharge alternative. CVWD monitored surface water flows and water quality and developed an initial recharge gallery design. Inflatable rubber dams will be used to divert flows from storm channels to recharge facilities. Implementation of the recharge program will improve water supply reliability and groundwater quality in the Basin and form a key component in the overall Basin water resources management.