Building the Foundation for a Fully Operational Water Bank
In 2025, the Sacramento Regional Water Bank (Water Bank) focused on
establishing the technical, analytical, and policy foundation needed to support future operations. The year was defined by clarifying how groundwater banking is measured, accounted for, and evaluated.
Key efforts included developing and releasing the Water Accounting System (WAS) framework, advancing the analysis of previously banked water accumulated through historic in-lieu and direct recharge, and defining an initial starting balance that reflects the recoverable volume remaining after accounting for systemwide contributions.
Together, this work established a shared understanding of how past banking actions have affected groundwater, rivers, and neighboring basins, and how those outcomes will be accounted for as the Water Bank moves toward formal environmental review and eventual operation.
Key Outcomes
Water Accounting System: A Major Milestone
The Regional Water Authority (RWA) completed and released the WAS framework. The WAS provides a clear, consistent, and transparent method for tracking how water moves into and out of the Water Bank—an essential step for building confidence in groundwater banking and supporting long-term sustainability.
The WAS establishes a structured approach to accounting for:
- Recharge and recovery, including both direct and in-lieu recharge
- Accounting benchmark that distinguishes banking activity from normal operations
- Measures to help ensure sustainability in the basin
- Forgone groundwater used to enable in-lieu recharge credits
- Storage rights and protocols governing access to banked water
Developed in coordination with local water suppliers, Groundwater Sustainability Agencies (GSAs), and technical experts, the WAS aligns with requirements of the Sustainable Groundwater Management Act (SGMA) and supports basin-wide coordination and reporting.
By establishing that recharge must occur before recovery, the WAS embeds sustainability safeguards directly into Water Bank operations. The framework also enhances transparency for in-lieu recharge, a foundational strategy of the Water Bank that allows groundwater levels to recover when surface water is used in place of pumping.
The release of the WAS marked a critical step in moving the Water Bank toward operational use and provided a working model for how groundwater accounting can support climate resilience and regulatory compliance.
Previously Banked Water: Quantifying Two Decades of Conjunctive Use
RWA completed a new, comprehensive technical analysis to quantify previously banked water (PBW) —water stored in the region’s groundwater basins over roughly the past two decades through coordinated conjunctive-use actions, primarily in-lieu recharge.
Using the region’s existing, calibrated groundwater and surface water model, local water suppliers analyzed surface and groundwater conditions from 1997 through 2024 to evaluate how banked water has moved through the interconnected system of aquifers, rivers, and adjacent basins. The analysis compared modeled conditions with and without groundwater banking actions to isolate the effects of long-term banking on groundwater storage, river baseflow, and interbasin groundwater movement.
The analysis found that approximately 900,000 acre-feet of water was banked during this period. Results show that this water has produced two distinct outcomes:
- About half of the previously banked water has left the North American and South American subbasins, contributing to rivers and neighboring groundwater basins. Modeling shows that increased groundwater levels reduced seepage losses from rivers to aquifers, resulting in increases in streamflow. On average, groundwater banking contributed approximately 14,000 acre-feet of additional baseflow per year to the lower American River. Since 1997, this equates to more than 310,000 acre-feet of additional flow to the lower American River and more than 370,000 acre-feet of combined flow to the American and Sacramento rivers. As groundwater levels rose, net groundwater subsurface outflow to adjacent subbasins also increased, extending benefits to neighboring basins.
- The remaining portion of previously banked water continues to be stored in the basin. This water is reflected in higher groundwater levels and sustained groundwater storage that remains available today, forming the basis for recoverable supply under the Water Bank.
Defining the Water Bank’s Starting Balance
These findings were a critical step toward defining a starting balance for the Water Bank. The starting balance represents the recoverable portion of previously banked water that remains in groundwater storage today, after accounting for the volume of water that has already contributed to rivers and neighboring basins over time. By explicitly accounting for these hydrologic outcomes, the analysis distinguishes between historical banking benefits that have already occurred and water that can be responsibly managed going forward.
Initial starting balance results were completed and shared with the Water Bank Program Committee in 2025. This work provides a scientifically defensible foundation for establishing the Water Bank’s initial account balance, avoids double-counting water that has already delivered environmental and regional benefits, and gives member agencies greater clarity and confidence as the Water Bank advances toward environmental review and eventual operation.
Stakeholder Engagement and Outreach
Engagement remained a core focus in 2025.
- Stakeholder Forum: RWA hosted its fourth Stakeholder Forum, providing updates on how the Water Bank works, its benefits, the Water Accounting System, and progress toward environmental review. Participants heard updates on planning documents, coordination efforts, and the Draft EIR process.
- Presentations and Briefings: Throughout the year, RWA staff provided briefings and presentations to a wide range of audiences, including:
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- The North State Building Industry Association
- Environmental Council of Sacramento (ECOS)
- Water Forum caucuses and cross-caucus meetings
- Water industry leaders at the ACWA Conferences, where RWA helped launch a new, jointly led effort to elevate the visibility of groundwater banking statewide. The initiative aims to strengthen collaboration among water banks in the state and increase recognition of water banking as a key strategy for climate adaptation and long-term water management across California.
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Looking Ahead: Anticipated 2026 Highlights
In 2026, the Sacramento Regional Water Bank is expected to transition from foundational planning into technical refinement and formal environmental review. Key activities expected in 2026 include:
- Developing a public-facing tool to support transparent tracking of recharge, recovery, leave-behind volumes, and basin conditions.
- Advancing technical analyses and modeling, including updated baseline and Water Bank scenarios using CalSim-CoSANA and expanded temperature modeling to better understand operational and environmental outcomes.
- Entering the core phase of environmental review, including finalizing the project description, preparing the Administrative Draft EIR, releasing the Public Draft EIR, and conducting public meetings.
- Continuing stakeholder engagement, including ongoing coordination with agencies, partners, and interested parties.
- Developing supporting technical and planning tools, including Streamflow Depletion Factor analysis, summary evaluation of shallow domestic wells, and template monitoring and adaptation planning.
- Advancing federal coordination, including developing a strategy to support NEPA review and federal acknowledgment.