Storing Water in the Ground for Future Use
Aquifer Storage and Recovery (ASR) is a water resource management technique that uses groundwater wells to recharge underground aquifers during times when water is available, then later recover that water from the aquifer when it is needed. The District was among the first agencies in the state to implement ASR by injecting treated water from Lake Cachuma into the Goleta Groundwater Basin to enhance natural recharge when Cachuma water was plentiful, and store it in the ground for use during dry periods. The ASR Program allows for the coordinated management of surface water and groundwater supplies, maximizing the availability and reliability of the District’s water resources.
The District’s ASR Program dates back to the 1970s. Back then, the injection method was simple: a hose connected to a fire hydrant was placed down a well and gravity pushed the water into the aquifer. This was a basic technique of recovering groundwater levels at the time. Forty years later, ASR remains a critical component of the District’s water resource management strategy, as described in the District’s foundational planning documents. Illustrating this, during the height of the recent severe drought, stored groundwater served as a lifeline source of supply for the Goleta Valley when surface water supplies were severely limited between 2015 and 2017.
The District currently has nine wells with a combined injection capacity of up to 2,600 acre-fee per year (AFY). During the February-June 2023 Cachuma spill event, the District used its wells to inject 815 acre-feet of water (228 million gallons) into the Goleta Groundwater Basin, helping to replenish underground water supplies that were drawn down during the drought. Prior to that, the District had not injected water since 2011, the last time Lake Cachuma spilled. The increasingly limited availability of surplus surface water due to the increased frequency and duration of droughts is the primary factor limiting the amount of water that can be injected. This is expected to become a bigger challenge driven by climate change.
To ensure groundwater remains a local, reliable, and sustainable source of supply for the Goleta Valley, the District is investing in and planning for necessary capital improvements that support the conjunctive use of water supplies, as detailed in the Infrastructure Improvement Plan. Projects include drilling new dual purpose (production/injection) wells to replace those that are near or approaching the end of their useful lives, investing in new groundwater treatment technologies, and upgrading pumps with more reliable and energy efficient models to support groundwater distribution throughout the system.
Additional information on the ASR Program and the District’s water resource management strategy are included in its water resource management documents, including the Groundwater Management Plan (GWMP) and Water Supply Management Plan (WSMP).