Question: What is in-lieu recharge and how does it work?

In-lieu recharge is the combined management of both surface water and groundwater use, resulting in the replenishment of groundwater supplies within our aquifers. This method combines managed and natural processes. Water agencies facilitate in-lieu recharge by directing excess surface water from lakes and rivers to customers who typically receive groundwater. Taking this action intentionally reduces groundwater use, which allows the aquifer to naturally replenish as rainwater, stormwater, and river water soak into the ground. The outcome is a stored (banked) reserve of groundwater supply for future use.

In-lieu recharge provides an opportunity to utilize excess river and lake water that otherwise would have been lost. This not only preserves groundwater for future use but also allows groundwater supplies to increase naturally in our aquifers.  

Question: Is in-lieu recharge recognized as a valid form of recharge in California?

In California, in-lieu recharge is widely acknowledged and is a proven method to sustainably replenish groundwater. In-lieu recharge has been put into practice for many decades and is endorsed by water managers, industry experts, state regulatory agencies, and academic institutions like the California Department of Water Resources, Public Policy Institute of California (PPIC), and Stanford University.

Moreover, California law recognizes in-lieu recharge as a groundwater sustainability action, as outlined in Water Code 10721 (m), which defines “In-Lieu” as the use of surface water by persons that could otherwise extract groundwater in order to leave groundwater in the basin. The implementation of in-lieu recharge is further included in the Sustainable Groundwater Management Act, which requires groundwater agencies to address its use in local sustainability plans.

Question: How does in-lieu recharge actually store water in the groundwater aquifer?

In-lieu recharge combines managed and natural processes to assist Mother Nature in replenishing groundwater supplies within our aquifers located deep below our feet. Due to the incorporation of natural recharge methods, the water storage process may seem less obvious than more visible recharge methods like spreading basins or injection wells. However, in-lieu recharge is widely acknowledged, with decades of practical application and a documented history of successfully replenishing the groundwater basin in the Sacramento region and other parts of California.

In-lieu recharge is a deliberate and scientifically grounded process that strategically manages and monitors groundwater resources to optimize replenishment. Although in-lieu recharge utilizes natural recharge processes, it requires deliberate efforts and planning by water agencies to work. Key water infrastructure, planning, and coordination of water agencies are critical for successfully substituting excess surface water for groundwater.

For example: For in-lieu recharge to occur, water agencies must incur costs from investing in infrastructure such as wells, pumps, and interconnections, and make critical management decisions. Without these actions, the in-lieu recharge process does not take place.

Moreover, in the Sacramento region, in-lieu recharge is informed by scientific assessments, considering factors such as water availability, demand, and aquifer geological characteristics. Local water managers continuously monitor water levels, quality, and recharge effectiveness, utilizing scientific data for adaptive management, helping to ensure the process remains effective over time.

Question: What is the Sacramento region’s history and experience with in-lieu recharge?

In the 1990s, groundwater levels were dropping drastically. Local water providers worked together to replenish groundwater through conjunctive use—coordinating the use of groundwater and surface water according to availability. In-lieu recharge was the primary method for recharge. Today, the Sacramento region’s groundwater levels have recovered and increased to sustainable levels.

Now, local water providers are working to elevate and expand in-lieu recharge by reoperating existing infrastructure. This is made possible through the Sacramento Regional Water Bank, an essential, cost-effective, and successful method for addressing climate change impacts on the region’s water supplies.

Question: What are some other agencies using in-lieu recharge in California?

In addition to the Sacramento region, in-lieu recharge is active in the following areas:

• Cawelo Water District (Kern County)
• Pixley Water Bank Project (Tulare County)
• Rosedale-Rio Bravo Water Storage District (Kern County)
• Semitropic Water Storage District (Kern County)
• Arvin Edison Water Storage District (Kern County)
• Buena Vista Water Storage District (Kern County)
• Kern Delta Water Storage District (Kern County)
• Orange County Water District (Orange County)