Peer Review of New Lines of Evidence for Effects on Fish from the Long-Term Operations of the Central Valley Project and State Water Project

Background

The 705-mile-long State Water Project (SWP) and 400-mile-long Central Valley Project (CVP) are complex networks of dams, reservoirs, canals, hydroelectric power plants, and facilities that deliver clean water to millions of Californians, hundreds of thousands of acres of farmland, and countless businesses throughout California. Long-term operations of the CVP and SWP seek to provide these services while maintaining water flows sufficient to protect wildlife and water quality in the Sacramento-San Joaquin Delta.

Past evaluations of CVP and SWP water operations have assessed various impacts of water exports on listed fish species in the Delta, including Delta smelt, longfin smelt, spring-run Chinook salmon, winter-run Chinook salmon, steelhead, and the southern distinct population segment of green sturgeon. Water exports may cause listed fishes to become entrapped in water diversions (entrainment) and may even contribute to fish mortality when fish are not in close proximity to CVP and SWP diversion facilities. However, critical uncertainties remain concerning: (1) where in the Delta these impacts may occur under different export operations, and (2) how export-induced hydrodynamic changes may influence fish populations in the tidal Delta.

New lines of evidence have been developed by the U.S. Bureau of Reclamation and Contra Costa Water District to better understand hydrodynamic and population responses associated with entrainment risk of listed fishes due to CVP and SWP water operations. These new lines of evidence include literature reviews, particle tracking modeling, life cycle analyses, and entrainment analyses. The new lines of evidence seek to refine the understanding of the spatial and temporal extent of export-induced hydrodynamic conditions and explore how associated fish mortality affects population-level responses.

The intent of this peer review is to provide Reclamation with recommendations to improve the methods utilized in the new lines of evidence for evaluating fish and aquatic effects of the long-term operations of the CVP and SWP.

Panel Letter Review

The Delta Science Program coordinates scientific peer reviews in accordance with its mission to provide the best possible unbiased scientific information to inform water and environmental decision-making in the Delta (Water Code Section 85280(b)(4)). As requested by Reclamation, the review will include a Panel Letter developed by the entire panel that addresses the review questions in the Charge based on the panel's collective expertise.

Access Reclamation’s request letter to Delta Lead Scientist, Dr. Lisamarie Windham-Myers

Access Dr. Windham-Myers's response to Reclamation

Panel Letter Review Materials

Review Documents (New Lines of Evidence)

1. Contra Costa Water District 2026. Intuitive Quantitative Metrics for Rapid Assessment of Entrainment Risks and Salmonid Responses in The Delta
2. USBR 2026. Summary of Modeling Used to Support the Weekly Delta Real-Time Forecast
3. USBR 2026. Assessing Operations and Environmental Conditions on Central Valley Chinook Salmon and Steelhead Juvenile Movement
4. USBR 2026. Literature Review of Juvenile Survival/Mortality Effects on Adult Populations for California Central Valley Chinook Salmon and Steelhead
5. USBR 2026. Smolt-to-Adult and Smolt-to-Salvage Modeling for Central Valley Chinook Salmon and Steelhead
6. USBR 2026. Interactive Object-Oriented Simulation Model for Winter-Run Chinook Salmon Sensitivity Analyses on Delta Mortality
7. USBR 2026. OBAN Sensitivity Analyses on Delta Mortality
8. USBR 2026. Winter-run Life Cycle Model Sensitivity Analyses on Delta Mortality
9. USBR 2026. Population-Level Consequences of Alternative Delta Export Operations for Sacramento River Winter-Run Chinook Salmon: A Life-Cycle Modeling Framework
10. USBR 2026. Data and Literature Review on Entrainment Versus Environmental Conditions for Central Valley Chinook Salmon and Steelhead

Supplemental Materials

1. USBR 2024a. Long-term Operation – Biological Assessment. Appendix I Old and Middle River Flow Management. Final EIS - Appendix AB-I: Old and Middle River Flow Management
2. USBR 2024b. Long-term Operation – Biological Assessment Appendix I Old and Middle River Flow Management Attachment I.3 Delta Export Zone of Influence. Final EIS - Lines of Evidence - Attachment I.3: Delta Export ZOI Analysis
3. USBR 2024c. Long-term Operation – Biological Assessment Appendix I Old and Middle River Flow Management – Attachment I.7 ECO-PTM. Final EIS - Lines of Evidence - Attachment I.7: ECO PTM
4. USBR 2025. Long-term Operation – Action 5. Exhibit 5, Entrainment Management. https://www.usbr.gov/mp/nepa/nepa_project_details.php?Project_ID=54661
5. National Academies of Sciences, Engineering, and Medicine. 2025. Review of the Long-Term Operations of the Central Valley Project and the State Water Project. Chapter 3 Old and Middle River Flow Management (pages 87-133). Washington, DC: The National Academies Press. https://doi.org/10.17226/29130
6. Delta Science Program 2026. Water Year 2024 and 2025 Winter-run Chinook Salmon Annual Loss Independent Peer Review. https://deltacouncil.ca.gov/delta-science-program/water-year-2024-and-2025-winter-run-chinook-salmon-annual-loss-independent-peer-review
7. California Department of Water Resources. California Data Exchange Center (CDEC). https://cdec.water.ca.gov/index.html

Additional Materials

• Access the Delta Science Program’s request for public input

Charge to the Independent Review Panel

The Charge to the independent review Panel provides the direction, context, and timeline for the review. The Charge includes orientation and focus for the review effort, support materials to be considered, and specific questions for the panel to address during the review process.

Access the Charge

Final Panel Report

• Final report expected December 2026

Review Panel Members

Dr. Erin Bray (Panel Chair)

San Francisco State University

Dr. Erin N. Bray is an Associate Professor in the School of the Environment (formerly Department of Earth and Climate Sciences) and leads the Rivers Lab at San Francisco State University. Previously, she was an Assistant Professor at California State University, Northridge, where she served as the Co-Lead for the Water Science Program. Dr. Bray’s research focuses on hydrology and geomorphology, with an emphasis on river mechanics, river restoration, and water resources management. She has developed a model that, together with field measurements and climate data, can be used to study the impacts of flow releases from dams and climate on the energy balance and water temperature of rivers. She also conducts field and laboratory experiments on fluvial abrasion, sediment transport, and hyporheic exchange, and how those processes generate and sustain salmon spawning habitat. Dr. Bray was a Postdoctoral Fellow at the University of California, Berkeley, and at the University of California, Santa Barbara, supported under a fellowship from the Delta Stewardship Council. She received her B.S. from Cornell University, her M.A. from Brown University, and her Ph.D. from the University of California, Santa Barbara.

Dr. Nancy Monsen (Lead Author)

Nancy E. Monsen, Ph.D.

Dr. Nancy Monsen’s research has focused on multidimensional hydrodynamic modeling of the Sacramento-San Joaquin Delta and Suisun Bay for the past 25 years. She earned her doctorate in Civil and Environmental Engineering at Stanford University. Her Ph.D. research was based on the TRIM3D hydrodynamic model, and more recently, she worked on Stanford’s SUNTANS hydrodynamic model. She also has consulting experience with the DELFT3d hydrodynamic model. Dr. Monsen joined Stanford University in August 2011, having worked previously with Philip Williams & Associates, Ltd. (now ESA PWA) and the U.S. Geological Survey (USGS). Funding for her Stanford research ended in August 2014, but she continued as a visiting scholar at Stanford until August 2015, writing papers and assisting Ph.D. candidates and post-doctoral researchers in the Environmental Fluid Mechanics Laboratory. Over the past 12 years, Dr. Monsen has served on several science review panels. Most recently, she participated in the 2024 Review of the Long-Term Operations for the Central Valley Project and State Water Project Fish and Aquatic Effects Analysis and chaired the Water Year 2024 and 2025 Winter-run Chinook Salmon Annual Loss Independent Peer Review. Dr. Monsen’s previous review panel work includes the Independent Review of the Draft Bay Delta Conservation Plan Effects Analysis (2014); the State of the Science Workshop on Fish Predation on Central Valley Salmonids in the Bay-Delta Watershed (2013); the Independent Review Expert Science Panel for the Collaborative Adaptive Management Team (CAMT) Proposed Investigations on Understanding Population Effects and Factors Affecting Entrainment of Delta Smelt at the State Water Project and Central Valley Project (2014); and the Calculation of Net Delta Outflow (NDO) Review (2016). She served as lead author for the 2017 CA WaterFix Aquatic Science Peer Reviews, Phases 2a and 2b. She also participated in the annual independent science review panels for the Long-term Operations of the Central Valley Project and State Water Project Biological Opinions (LOBO) in 2014, 2015, and 2017, as well as the NMFS 2019 Independent Review of the Coordinated Long-Term Operation of the Central Valley Project and State Water Project.

Dr. Stephen Brandt

Brandt Scientific Consultants LLC

Dr. Stephen B. Brandt is a Professor Emeritus in the Department of Fisheries, Wildlife, and Conservation Sciences at Oregon State University, where he specializes in fish ecology and management in marine and freshwater ecosystems. He served as the Director of the Oregon Sea Grant Program and chaired the university’s inaugural Marine Council. Previously, he held faculty positions at the University of Maryland’s Chesapeake Biological Laboratory, SUNY College at Buffalo, and SUNY ESF, Syracuse, and spent 5 years studying deep-sea fishes off Australia. Dr. Brandt directed the NOAA Great Lakes Environmental Research Laboratory for 12 years and earned the President’s Rank Award. There, he created the NOAA Invasive Species Center and created and led the NOAA Center of Excellence for Great Lakes and Human Health. He has written over 150 publications (H-index = 51) and given over 300 scientific presentations on food webs, fish bioenergetics and habitat quality, physical/biological interactions, hypoxia, and ecosystem forecasting spanning the Great Lakes, Chesapeake Bay, Gulf of Mexico, Adriatic Sea, South Pacific, Western Atlantic, California Delta, and small lakes. Dr. Brandt received his M.S. and Ph.D. in Oceanography and Limnology from the University of Wisconsin, Madison. He was elected President of the International Association for Great Lakes Research and received their highest award. He served 10 years on the Delta Independent Science Board, during which he was elected chair twice. He also spent over 10 years as the OSU representative on the Oregon Watershed Enhancement Board. He recently completed a two-year appointment to a National Academy of Sciences Committee evaluating water operations and environmental impacts on the California Delta.

Dr. Richard W. Zabel

Zabel Ecoscience LLC

Dr. Zabel’s research has focused on the population dynamics, bioenergetics, and behavior of fish, especially in relation to climate change and human impact. Key areas of his work include: Population viability modeling: Using demographic models to assess the viability of fish populations and the effects of factors like density dependence and anthropogenic impacts, and then using the models to forecast alternative future scenarios; Climate impacts: Studying how climate variability and change affect fish populations; Migrational behavior: Modeling dispersal patterns and life history traits in fish, including examining how environmental conditions affect the migration of salmon populations; Hydropower impacts: Assessing the effects of hydropower development on fish through the development of decision-support tools. Rich earned a B.S. and M.S. from the University of Michigan and a Ph.D. in Quantitative Ecology and Resource Management from the University of Washington.