Colorado River Basin Water Management

Evaluating and Adjusting to Hydroclimatic Variability

Committee on the Scientific Bases of Colorado River Basin Water Management

Water Science and Technology Board

Division on Earth and Life Studies

NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES

THE NATIONAL ACADEMIES PRESS

Washington, D.C.
www.nap.edu



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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability Colorado River Basin Water Management Evaluating and Adjusting to Hydroclimatic Variability Committee on the Scientific Bases of Colorado River Basin Water Management Water Science and Technology Board Division on Earth and Life Studies NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES THE NATIONAL ACADEMIES PRESS Washington, D.C. www.nap.edu

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability THE NATIONAL ACADEMIES PRESS 500 Fifth Street, N.W. Washington, DC 20001 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the panel responsible for the report were chosen for their special competences and with regard for appropriate balance. Support for this study was provided by the National Research Council’s Day Fund, the U.S. Bureau of Reclamation under contract number 05PG303309, the California Department of Water Resources, the Metropolitan Water District of Southern California under contract number 77624, and the Southern Nevada Water Authority. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project. International Standard Book Number-13: 978-0-309-10524-8 International Standard Book Number-10: 0-309-10524-2 Additional copies of this report are available from the National Academies Press, 500 5th Street, N.W., Lockbox 285, Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); Internet, http://www.nap.edu. Cover: Tree-ring cross section photograph courtesy of Connie Woodhouse. Glen Canyon Dam and Lake Powell (2004) photograph courtesy of Brad Udall. Skyline photograph of Las Vegas, NV provided by the U.S. Bureau of Reclamation at http://www.usbr.gov/dataweb/html/ griffith.html. Formal portrait of John Wesley Powell circa 1890’s from the U.S. National Park Service’s Grand Canyon National Park Museum Collection. Copyright 2007 by the National Academy of Sciences. All rights reserved. Printed in the United States of America.

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability THE NATIONAL ACADEMIES Advisers to the Nation on Science, Engineering, and Medicine The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Wm. A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Wm. A. Wulf are chair and vice chair, respectively, of the National Research Council. www.national-academies.org

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability COMMITTEE ON THE SCIENTIFIC BASES OF COLORADO RIVER BASIN WATER MANAGEMENT* ERNEST T. SMERDON, Chair, University of Arizona (Emeritus), Tucson JULIO L. BETANCOURT, United States Geological Survey, Tucson, Arizona GORDON W. “JEFF” FASSETT, HDR Engineering, Inc., Cheyenne, Wyoming LUIS A. GARCIA, Colorado State University, Fort Collins DONALD C. JACKSON, Lafayette College, Easton, Pennsylvania DENNIS P. LETTENMAIER, University of Washington, Seattle ELUID L. MARTINEZ, Water Resources Management Consultants, Santa Fe, New Mexico STEPHEN C. McCAFFREY, University of the Pacific, Sacramento, California EUGENE M. RASMUSSON, University of Maryland (Emeritus), College Park KELLY T. REDMOND, Desert Research Institute, Reno, Nevada PHILIP M. SMITH, Science Policy and Management, Santa Fe, New Mexico CONNIE A. WOODHOUSE, University of Arizona, Tucson NRC Staff JEFFREY W. JACOBS, Study Director DOROTHY K. WEIR, Research Associate * The activities of this committee were overseen and supported by the National Research Council’s Water Science and Technology Board (see Appendix C for listing). Biographical information on committee members and staff is contained in Appendix D.

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability Preface The Colorado River has long been uniquely important in the exploration, development, and culture of the western United States. The Colorado is a desert river, stretching from high in the Rockies, through great canyons and arid regions in Utah and Arizona, and finally ending in the Gulf of California in Mexico. For millions of years it has shaped landforms and in the Grand Canyon has exposed geologic formations that are half as old as the Earth itself. The great American scientist John Wesley Powell explored this region widely. He had extensive knowledge of many Native American tribes and his 1869 boating expedition down the Colorado River through the Grand Canyon is legendary. Powell’s 1878 publication Lands of the Arid Region of the United States, with a More Detailed Account of the Lands of Utah offered many new ideas regarding the roles of the U.S. federal government in developing western water supplies. Although Powell may have foreseen some aspects of western development, one thing he probably did not foresee was the future extent of population growth in the Colorado River region. Nor was Powell likely to have imagined that changes in regional climate might someday affect hydrologic conditions. Our committee was asked to review the hydrologic and climatic bases of Colorado River water management. In considering this existing body of scientific information, we were struck by the warming across the region in the past century and by the fact that nearly all global climate models forecast increasing temperatures for the Colorado River region. We also noted the exceptionally hot and dry conditions across much of the nation in the summer of 2006, and that the 2006 average annual temperature for the contiguous United States was the warmest on record and nearly identical to the record

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability set in 1998. These conditions are consistent with warming trends in the region. As we proceeded it became clear that a broad understanding of Colorado River water management issues is not possible unless both water supply and demand issues are adequately considered. Terms such as “population growth” and “water demand” did not appear in our statement of task. As we spoke with water experts from across the region at our meetings, however, they identified important linkages among hydrology and climate and issues such as population growth and water demands, urban water management and conservation, riparian ecology, and water transfers. Clearly, interest in hydroclimatic issues in the region is being driven in large part by increasing water demands and a limited ability to augment water supplies through traditional means. Furthermore, our statement of task called for us to consider the broad topics of systems operations and water management practices. We thus felt it incumbent upon us to comment on topics of water demand, technologies and practices for augmenting water supplies, and programs for coping with drought. Our report presents population growth data for much of the western United States that is served by Colorado River water. The cities in the region are collectively the fastest growing in the nation. Of further concern is that this growth seems to be occurring with little regard to long-term availability of future water supplies. Ideally, these issues will be openly discussed and squarely addressed before the water supply-and-demand balance across the region becomes more critical. This is important because, for example, the drought of the early 2000s turned out to be even worse than many assumptions regarding a worst-case-scenario drought. This ongoing drought has contained a sequence of exceptionally dry years. Inflows into the basin’s storage reservoirs have been well below normal and it may take 15 years of average future hydrologic conditions to refill the basin’s largest water storage reservoirs, Lakes Mead and Powell. These hydroclimatic trends are especially troubling in light of rapidly increasing water demands. I thank our committee members for the hard work and intellect they devoted to producing this consensus report. Each of them brought unique expertise to our deliberations and report preparation and they all devoted many hours of personal time to our study. Their views were fully considered in our study process and I thank them for

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability their contributions, good will, and spirit of collaboration. I also thank the many water scientists, engineers, administrators, and other experts from across the region that spoke with our committee. They provided a comprehensive and fascinating update of key water and science issues across the region and presented important topics and questions for our committee’s consideration, all of which were essential to our deliberations and report (Appendix B lists these speakers). I also thank the National Research Council (NRC) staff members for their dedication and diligent work in our study process. Jeff Jacobs, senior staff officer with the Water Science and Technology Board (WSTB), ensured that our committee stayed on task and that the varying opinions and written contributions from our committee members were blended to create a single, coherent report. Jeff and the committee were ably assisted by WSTB research associate Dorothy Weir, who handled administrative details of the meetings and ably assisted in all phases of report preparation. We are grateful to the sponsors who provided support for this study. These sponsors included federal, state, and municipal water organizations across the West, which reflects the broad interest in and importance of in these issues. These sponsors were the California Department of Water Resources, the Metropolitan Water District of Southern California, the Southern Nevada Water Authority, and the U.S. Bureau of Reclamation. We also thank the National Academies for providing a substantial portion of funding and for exercising leadership in initiating this study. This report was reviewed in draft form by individuals chosen for their breadth of perspectives and technical expertise in accordance with the procedures approved by the National Academies’ Report Review Committee. The purpose of this independent review was to provide candid and critical comments to assist the institution in ensuring that its published report is scientifically credible and that it meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The reviewer comments and draft manuscript remain confidential to protect the deliberative process. We thank the following reviewers for their helpful suggestions, all of which were considered and many of which were wholly or partly incorporated in the final report: John A. Dracup, University of California; Jerome B. Gilbert, Orinda, California; W.R. Gomes, University of California; Martin P. Hoerling, National Oceanic and

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability Atmospheric Administration; Malcolm K. Hughes, University of Arizona; Katharine L. Jacobs, University of Arizona; John W. Keys, III, Moab, Utah; Upmanu Lall, Columbia University; John E. Thorson, California Public Utilities Commission; and James L. Wescoat, Jr., University of Illinois. Although these reviewers provided constructive comments and suggestions, they were not asked to endorse the report’s conclusions and recommendations nor did they see the final draft of the report before its release. The review of this report was overseen by Daniel P. Loucks, Cornell University, who was appointed by the NRC’s Report Review Committee, and by A. Dan Tarlock, Chicago Kent College of Law, who was appointed by the NRC’s Division on Earth and Life Studies. Drs. Loucks and Tarlock were responsible for ensuring that an independent examination of this report was conducted in accordance with NRC institutional procedures and that all review comments received full consideration. Responsibility for this report’s final contents rests entirely with the authoring committee and the NRC. The seven Colorado River basin states and cooperating agencies, particularly the Bureau of Reclamation, face great challenges in addressing the complex issues of Colorado River water supply management. The pressures of meeting the needs of the burgeoning population in the face of future severe droughts and uncertain impacts of global change are indeed great. Political pressures will abound but there are signs of increasing cooperation on a variety of water use issues. We hope this report represents a contribution to the knowledge base of Colorado River hydroclimate and water management and that it helps promote common understanding and cooperation on these matters. Ernest T. Smerdon Chair

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability Contents     SUMMARY   1 1   INTRODUCTION   13      Water Supply Conditions and Hydroclimatic Studies,   17      Statement of Task and Scope of Report,   19 2   HISTORICAL AND CONTEMPORARY ASPECTS OF COLORADO RIVER DEVELOPMENT   26      Early Exploration and Initial Forays in Colorado River Development: 1860s to 1920,   29      Large-Scale Colorado River Water Development: 1920 to 1965,   31      Relative Surplus and Shifting Priorities: 1965 to the Mid-1980s,   44      Tightening Supplies and Increasing Demands: Mid-1980s to the Present,   48      Commentary,   69 3   CLIMATE AND HYDROLOGY OF THE COLORADO RIVER BASIN REGION   73      Features and Dynamics of Colorado River Basin Climate,   74      Climate Trends and Projections,   80      Instrumental Record of Colorado River Streamflow,   92      Tree-Ring Science and Reconstructed Streamflow Records,   99      Commentary,   108 4   PROSPECTS FOR CONSERVING AND EXTENDING WATER SUPPLIES   112      Large-Scale Reservoirs and Inter-Basin Transfers,   113      Cloud Seeding,   115      Desalination,   118      Removing Water-Consuming Invasive Species,   122

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability      Agricultural Water Conservation,   123      Urban Water Conservation,   124      Offstream Water Banking and Reserves,   127      Commentary,   131 5   COLORADO RIVER BASIN DROUGHT PLANNING STRATEGIES AND ORGANIZATIONS   133      Federal-Level Programs,   135      State-Level Programs,   138      Municipal-Level Programs,   141      Other Organizations and Initiatives,   143      Commentary,   147 6   EPILOGUE   151     REFERENCES   155     APPENDIXES          A  Letter to Secretary of the Interior Gale A. Norton from the States of Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming Governor’s Representatives on Colorado River Operations   175      B  Guest Speakers at Committee Meetings   201      C  Water Science and Technology Board   203      D  Biographical Information for Committee on the Scientific Bases of Colorado River Basin Water Management   205