By Jim Peifer, Executive Director of the Regional Water Authority
In the late 1990s, Sacramento-area water providers worked together to address an alarming, decades-long decline in the region’s groundwater supply. Today, that collaboration is producing benefits far beyond groundwater recharge.
A recently completed analysis confirms the benefits of groundwater banking—not only on the Sacramento region’s groundwater supplies but also the positive effects groundwater banking is having on our creeks and rivers. Over the last couple of decades, groundwater banking has contributed to a net increase of 14,000 acre-feet of additional baseflow every year to the lower American River.
Put simply, groundwater banking actions are providing broad local and regional benefits, including water supply reliability, support for river and ecosystem health, and sustainable groundwater supplies. By improving conditions in rivers and neighboring basins, and supporting water reliability and groundwater sustainability, this approach shows how collaborative management produces durable, multi-benefit outcomes.
Banked water provides multiple benefits
This recent analysis on the effectiveness of banked water comes from analyzing surface and groundwater conditions in the region from 1997 to 2024 and comparing the volume of water stored in the aquifer with and without these banking actions.
To do this, local water providers used the region’s existing groundwater model to run an analysis focused on how water moves between rivers, aquifers, and adjacent basins. The model, calibrated with actual water and groundwater data, demonstrates that banked water has both remained in the local aquifers and enhanced flows in connected rivers and adjacent basins. These processes convey considerable environmental benefits.
Here’s how they work:
Rivers and groundwater aquifers are hydrologically interconnected in our region. When groundwater levels increase or decrease, it affects how much water flows through rivers, streams, and creeks. By raising groundwater levels through banking, less surface water seeps downward into the aquifer. The result is more water remaining in the lower American River—thousands of acre-feet that support salmon, improve water temperatures, and contribute to Delta conditions downstream.
Altogether, banked water has contributed more than 310,000 acre-feet of flow to the lower American River since 1997 and more than 370,000 acre-feet to the American and Sacramento rivers combined.
Just as rivers aren’t isolated from aquifers, aquifers are also not isolated from each other. As the water table rises, the net outflow of water from our local aquifers to aquifers in adjacent sub-basins increases, contributing to the groundwater supplies in those regions.
This means the benefits of banked water are shared—helping our river, helping neighboring regions, and helping statewide water management at times when it matters most.
Long-term investments pay off
These impressive results required long-term collaboration across 19 local agencies, significant investments in infrastructure, and a shared commitment to the lower American River.
When agencies agreed to start using in-lieu recharge to reverse groundwater depletion back in the 1990s, not every agency had the ability to flexibly switch between groundwater and surface water. For in-lieu recharge to work on a larger scale, some agencies had to invest in pumping and conveyance infrastructure that allows them to purchase surface water from other agencies.
Constructing and operating this dual infrastructure came with considerable costs, but the investment was worth it to provide long-term reliability and a more resilient, sustainable groundwater system. The groundwater modeling results illustrate that these investments raised groundwater levels by as much as 20 feet in some areas, initially stabilizing then reducing cones of depression and improving water supply reliability.
Now, we’re in the position to expand and enhance our region’s ability to bank water through in-lieu and direct recharge methods with the Water Bank. The Water Bank builds on this proven track record and adds the incentive structure needed to encourage even more recharge—crediting agencies for the water they store and for the environmental contributions their actions create. This critical groundwater storage program will improve regional water supply reliability now and into the future, even as we face more frequent extremes on both ends–prolonged drought and intense wet years—that we know are coming with climate change.
What’s next for the Water Bank
Earlier this year, we developed a Water Accounting System, a framework that will allow water providers to accurately and transparently track water movement into and out of the Water Bank. The new modeling results provide scientific justification to set a “starting balance”—the recoverable volume of previously banked water remaining in storage after accounting for contributions to rivers and neighboring basins—and gives local water providers confidence as we move forward with the Water Bank.
Building on decades of regional water management experience, these results demonstrate the long-term benefits of coordinated groundwater storage and management in our region.
Looking ahead, local water providers will continue to bank water through in-lieu and direct recharge, while tracking how much water is stored and how much contributes to streamflow and neighboring aquifers. Over the next one to two years, environmental documentation and additional modeling will evaluate future banking scenarios and guide operations. The Water Bank is expected to be fully operational in 2027.
Taken together, these efforts demonstrate that enhanced groundwater management is one of the most effective, scalable, and cost-effective ways to secure long-term water supply reliability in California—positioning the American River region to pursue Proposition 4 funding and to lead the way in climate adaptation. Collaboration got us here—and it will keep paying off.
Jim Peifer is Executive Director of the Regional Water Authority, representing nearly two dozen water suppliers serving 2.2 million people in the Sacramento region. He can be reached at jpeifer@rwah2o.org.
