Final Monitoring Special Study Report Advances Scientific Understanding of Delta Hydrodynamics and Water Quality

SACRAMENTO, Calif. - The Bureau of Reclamation and the California Department of Water Resources have released the Final Monitoring Special Study Report, marking an important milestone in advancing the scientific understanding of hydrodynamic and water quality conditions in the Sacramento-San Joaquin Delta. Because the Delta supplies water to millions of Californians and supports vital agricultural, environmental, and economic uses, improving the scientific foundation behind management decisions is crucial.

The report provides state-of-the-art scientific analyses that improve understanding of the complex physical processes influencing flow and salinity in the Delta. By reducing scientific uncertainty and strengthening the technical foundation for future evaluations, the study supports more informed water management decisions, contributes to greater regulatory certainty, and helps advance reliable water supplies while protecting environmental resources.

"The Monitoring Special Study Report reflects years of scientific analysis and technical collaboration to improve our understanding of the complex processes that influence the Delta," said Reclamation's Central Valley Operations Manager Levi Johnson. "Better science leads to better understanding and decisions. These enhanced monitoring and modeling tools provide a stronger foundation for evaluating water management strategies, supporting informed regulatory decisions, and helping improve long-term water supply reliability for the many stakeholders who rely on the Delta."

Developed in response to the State Water Resources Control Board's 2018 amendments to the Bay-Delta Water Quality Control Plan, the report provides a comprehensive evaluation of the physical processes that influence flow and salinity conditions in the southern Delta. The study supports future monitoring efforts and provides technical information to help inform implementation of the Bay-Delta Plan's salinity objectives.

The report incorporates state-of-the-art three-dimensional hydrodynamic modeling and data analyses to evaluate how water levels, flow, and salinity respond under a range of hydrologic and operational conditions. The findings improve future modeling capabilities, reduce scientific uncertainty, and provide water managers and regulators with more robust analytical tools for evaluating future operational scenarios. The enhanced monitoring and modeling tools help inform regulatory processes by reducing scientific uncertainty and providing clearer insights into how different operational choices shape flow and salinity outcomes.

Reclamation and the California Department of Water Resources developed the Monitoring Special Study in close coordination with other technical partners through an extensive collaborative process that included technical workgroups, agency coordination, public coordination meetings, and opportunities for review and comment from interested parties. The report synthesizes the results of more than eight technical studies examining salinity monitoring, data assimilation, hydrodynamic modeling, and water quality characterization throughout the southern Delta.

"By improving our understanding of Delta conditions, this report helps strengthen the scientific basis for future regulatory and operational decisions," added Johnson. "This benefits water users, resource managers, and the environment by providing greater confidence in how we plan for California's water future."

Reclamation remains committed to advancing the best available science through continued technical innovation and collaboration with state, federal, and local partners to address California's evolving water management challenges. The Monitoring Special Study marks an important step toward more adaptive, science-driven management of California's water systems.

The Final Monitoring Special Study Report, technical documentation and detailed information on coordination meetings and study development are available on the California Department of Water Resources website.

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The Bureau of Reclamation is a federal agency under the U.S. Department of the Interior and is the nation's largest wholesale water supplier and second largest producer of hydroelectric power. Our facilities also provide substantial flood control, recreation opportunities, and environmental benefits.