Date:  March 29, 2012




Increasing Water Scarcity in California's Bay-Delta Will Necessitate Trade-offs; 'Hard Decisions' Needed to Balance Various Environmental Risks


WASHINGTON — Simultaneously attaining a reliable water supply for California and protecting and rehabilitating its Bay-Delta ecosystem cannot be realized until better planning can identify how trade-offs between these two goals will be managed when water is limited, says a new report from the National Research Council.  Recent efforts have been ineffective in meeting these goals because management is distributed among many agencies and organizations, which hinders development and implementation of an integrated, comprehensive plan.  Additionally, it is impossible to restore the delta habitat to its pre-disturbance state because of the extensive physical and ecological changes that have already taken place and are still occurring, including those due to multiple environmental stressors. 


The delta region receives fresh water from the Sacramento and San Joaquin rivers and their tributaries, and ultimately flows into San Francisco Bay and the Pacific Ocean.  Water-pumping stations divert water from the delta, primarily to supply Central Valley agriculture and metropolitan areas in southern California, the Bay Area, and the delta itself.  An increasing population and the operation of the engineered water-control system have substantially altered the delta ecosystem, including its fish species.  Conflicts among various water users have grown, and there are sharp differences of opinion concerning the timing and amount of water that can be diverted from the delta for agricultural, municipal, and industrial purposes and how much water, and of what quality, is needed to protect the delta ecosystem.  The U.S. Department of the Interior asked the National Research Council to identify the factors affecting fish species in the delta, review future water supply and delivery options, determine gaps in knowledge, and advise on the degree of delta restoration that is attainable while maintaining both an environmentally sustainable ecosystem and a reliable water supply. 


It is likely that water scarcity in the delta will become increasingly severe, the report says.  Failure to acknowledge this problem and craft plans and policies that address water scarcity for all needs has made delta water management more difficult than is necessary.  The committee that wrote the report suggested establishing priorities for water use, accounting for trade-offs in decision making, optimizing the availability of existing water supplies, enforcing California's constitutional prohibition against non-beneficial and wasteful water use, and practicing water conservation, among other principles and guidelines.


Multiple environmental stressors -- such as dams; water pumping stations; introduced and invasive species; and changes in nitrogen and phosphorus concentrations and amounts, water flow, and habitat -- negatively affect five delta fishes listed as endangered or threatened, the committee said.  Successfully rehabilitating the delta ecosystem by targeting how an individual stressor impacts a particular species seems doubtful.  Therefore, hard decisions will need to be made about balancing risks for different water uses, such as allocating water to support economic activity, sanitation, or other needs.  In addition, alleviating any one stressor alone is unlikely to reverse declines in these species, but opportunities exist to mitigate or reverse the effects of many stressors.  To increase the likelihood that actions to rehabilitate the ecosystem are cost-effective, continued analyses, modeling, and monitoring will be needed, the committee noted.    


Climate change is one of the most challenging and important issues confronting the management and rehabilitation of the delta ecosystem.  It is expected to affect the physical and ecological structure and functioning of the delta as well as the availability of water in the state.  For instance, assessments suggest that many species will be affected by changes in runoff from precipitation and snowmelt, which would likely occur earlier in the year than currently.  In addition, projected sea-level rise and extremes of precipitation could increase the frequency of levee failure and the inundation of islands.  Sea-level rise also has the potential to move more salt water into the delta and alter water quality.  The committee recommended that future planning should include a climate change-based risk model, analysis that incorporates data on the actual changes in delta conditions, and alternative future climate scenarios and their probability.


Additionally, the instability of levees and potential of one levee failure to affect others are liable to be major issues for achieving any measure of water supply reliability or ecosystem rehabilitation.  Continuing the status quo of improving levees will not always be the most environmentally sustainable or economically defensible response in the years ahead, the committee noted.


The lack of integrated, comprehensive planning has made science less useful in decision making for the delta, the committee said.  It recommended that California review water planning and management in anticipation of future circumstances.  This review should devote attention to water scarcity, balanced consideration of all statewide water uses and the practices that govern them, and available engineering alternatives.  In the absence of a review, it would be difficult to resolve delta water management problems in other than a piecemeal fashion.  


"Science is necessary to inform actions and proposals, but it does not provide the entire overview and integration that the committee recommends," said committee member Henry J. Vaux Jr., professor emeritus of resource economics at the University of California.  "Societal and political considerations are also integral factors in determining the most appropriate policies toward managing the water resources in the delta and balancing the needs of all water users."


The study was sponsored by the U.S. Department of the Interior. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies.  They are independent, nonprofit institutions that provide science, technology, and health policy advice under an 1863 congressional charter.  Committee members, who serve pro bono as volunteers, are chosen by the Academies for each study based on their expertise and experience and must satisfy the Academies' conflict-of-interest standards.  The resulting consensus reports undergo external peer review before completion.  For more information, visit  A committee roster follows.




Jennifer Walsh, Media Relations Officer

Luwam Yeibio, Media Relations Assistant

Office of News and Public Information

202-334-2138; e-mail


Pre-publication copies of Sustainable Water and Environmental Management in California’s Bay-Delta, is available from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at  Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).

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Division on Earth and Life Studies

Water Science and Technology Board


Committee on Sustainable Water and Environmental Management in the California Bay-Delta


Robert J. Huggett (chair)

Professor Emeritus

College of William and Mary

Seaford, Va.


James J. Anderson

Research Professor and Co-Director of Columbia Basin Research

School of Aquatic and Fishery Sciences

University of Washington



Michael E. Campana


Department of Geosciences

Oregon State University



Thomas Dunne1


Donald Bren School of Environmental Science and Management

University of California

Santa Barbara


Jerome B. Gilbert2

Consulting Engineer

Orinda, Calif.


Albert E. Giorgi

President and Senior Fisheries Scientist

BioAnalysts Inc.

Redmond, Wash.


Christine A. Klein

Chesterfield Smith Professor of Law

College of Law

University of Florida


Samuel N. Luoma


U.S. Geological Survey

Menlo Park, Calif.


Thomas Miller


Chesapeake Biological Laboratory

Center for Environmental Science

University of Maryland



Stephen G. Monismith

Associate Professor

Civil Engineering Department

Terman Engineering Center

Stanford University

Stanford, Calif.


Jayantha Obeysekera

Director of Hydrologic and Environmental Systems Modeling

South Florida Water Management District

West Palm Beach


Hans W. Paerl

Distinguished Professor

Institute of Marine Sciences

University of North Carolina

Morehead City


Max J. Pfeffer


Department of Rural Sociology

Cornell University

Ithaca, N.Y.



Denise Janet Reed


Department of Earth and Environmental Sciences

Pontchartrain Institute for Environmental Sciences

University of New Orleans

New Orleans


Kenneth A. Rose

E.L. Abraham Distinguished Professor

Department of Oceanography and   

   Coastal Sciences

Louisiana State University

Baton Rouge


Desiree D. Tullos

Assistant Professor

Department of Biological and Ecological Engineering

Oregon State University



Henry J. Vaux Jr.

Professor Emeritus of Resource Economics

University of California

El Cerrito





David Policansky

Study Director


1 Member, National Academy of Sciences

2 Member, National Academy of Engineering