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i MEXICO CITY'S WATER SUPPLY Improving the Outlook for Sustainability The Joint Academies Committee on the Mexico City Water Supply Water Science and Technology Board Commission on Geosciences, Environment, and Resources National Research Council and Academia Nacional de la InvestigaciÃ³n CientÃfica, A.C. Academia Nacional de IngenierÃa, A.C. NATIONAL ACADEMY PRESS Washington, D.C. 1995
ii 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 board responsible for the report were chosen for their special competencies and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sci- ences, the National Academy of Engineering, and the Institute of Medicine. Support for this project was provided by the Ford Foundation under Agreement No. 910â1413, the Tinker Foundation, the U.S. Environmental Protection Agency under Agreement No. CX-820728â01â0, the Mexico National Science and Technology Council (CONACYT), the Mexico Ministry of Health, the United Nations Development Program, the National Research Council Fund, the Rockefeller Foundation, and the MacArthur Foundation. About the Cover: Paisaje by Emilio Rosenblueth, oil on canvas, 1938; collection of the Rosen- blueth family. Use of this painting is in memory of Emilio Rosenblueth, Jr. (1926â1994), son of the artist, who did much for the advancement of science in Mexico and was so instrumental in building bridges to the scientific community in the United States. Dr. Rosenblueth, Jr. was director of the Institute of Engineering of the National University of Mexico (UNAM), the dean of science for the university, president of the Academy of Science (AIC), vice-minister of the Ministry of Education, and foreign associate member of NAS and NAE. Special thanks to Sra. Alicia Laguette de Rosen- blueth, wife and companion of Emilio, and his family for permission to reprint. Library of Congress Catalog Card No. 95â67404 International Standard Book Number 0-309-05245-9 Additional copies of this report are available from: National Academy Press 2101 Constitution Ave., NW Box 285 Washington, DC 20055 800â624â6242 202â334â3313 (in the Washington Metropolitan Area) B-533 Copyright 1995 by the National Academy of Sciences. All rights reserved. Printed in the United States of America
iii COMMITTEE ON THE MEXICO CITY WATER SUPPLY CHARLES T.DuMARS, co-Chair, University of New Mexico, Albuquerque ISMAEL HERRERA-REVILLA, co-Chair, Academia Nacional de IngenierÃa, A.C., and Instituto de GeofÃsica, UNAM, MÃ©xico. D.F. IRINA CECH, University of Texas, Houston RANDALL CRANE, University of California, Irvine CRISTINA CORTINAS-DE NAVA, Instituto Nacional de EcologÃa de la SecretarÃa de Desarrollo Social, MÃ©xico, D.F. JOSE RAMÃN COSSÃO-DÃAZ, Suprema Corte de Justicia de la NaciÃ³n, MÃ©xico, D.F. RICHARD S.ENGELBRECHT, University of Illinois at Urbana-Champaign ROBERT N.FARVOLDEN, University of Waterloo, Canada, and National Ground Water Association, Dublin, Ohio HELEN INGRAM, University of Arizona, Tucson JESUS KUMATE-RODRÃGUEZ, SecretarÃa de Salud, MÃ©xico, D.F. LUCRECIA LOZANO-GARCÃA, Instituto TecnolÃ³gico y de Estudios Superiores de Monterey, Nuevo LeÃ³n, MÃ©xico JUAN MANUEL MARTINEZ-GARCÃA, DirecciÃ³n General de ConstrucciÃ³n y OperaciÃ³n HidrÃ¡ulica del Departamento del Distrito Federal, MÃ©xico, D.F. RUBÃN MARTÃNEZ-GUERRA, ComisiÃ³n Nacional del Agua, MÃ©xico, D.F. CARLOS VÃLEZ-OCÃN, Instituto Nacional de Investigaciones Nucleares, MÃ©xico, D.F. DAVID WILK-GRABER, Consultor en desarrollo urbano y medio ambiente, MÃ©xico, D.F. WSTB LIAISON KENNETH D.FREDERICK, Resources for the Future, Washington, D.C. STAFF FOR THE COMMITTEE GARY D.KRAUSS, Study Director, Water Science and Technology Board, National Research Council JULIA MELCHOR-SÃNCHEZ, Study Director, FundaciÃ³n Ricardo Monges LÃ³pez, A.C. ALEJANDRO LOZANO-GUZMÃN., Study Director, Academia Nacional de IngenierÃa, A.C. GREGORY NYCE, Project Assistant, Water Science and Technology Board, National Research Council
iv WATER SCIENCE AND TECHNOLOGY BOARD DAVID L.FREYBERG, Chair, Stanford University, California BRUCE E.RITTMANN, Vice Chair, Northwestern University, Evanston, Illinois LINDA M.ABRIOLA, University of Michigan, Ann Arbor J.DAN ALLEN, Chevron USA, Inc., New Orleans, Louisiana PATRICK L.BREZONIK, University of Minnesota, St. Paul WILLIAM M.EICHBAUM, The World Wildlife Fund, Washington, D.C. WILFORD R.GARDNER, University of California, Berkeley WILLIAM L.GRAF, Arizona State University, Tempe THOMAS M.HELLMAN, Bristol-Myers Squibb Company, New York, New York CHARLES C.JOHNSON, U.S. Public Health Service (Retired), Washington, D.C. CAROL A.JOHNSTON, University of Minnesota, Duluth WILLIAM M.LEWIS, JR., University of Colorado, Boulder CAROLYN H.OLSEN, Brown and Caldwell, Pleasant Hill, California CHARLES R.O'MELIA, John Hopkins University, Baltimore, Maryland IGNACIO RODRIGUEZ-ITURBE, Texas A&M University, College Station HENRY VAUX, JR., University of California, Riverside Staff STEPHEN D.PARKER, Director SHEILA D.DAVID, Senior Staff Officer CHRIS ELFRING, Senior Staff Officer JACQUELINE MACDONALD, Senior Staff Officer GARY D.KRAUSS, Staff Officer ETAN GUMERMAN, Research Associate JEANNE AQUILINO, Administrative Associate ANITA A.HALL, Administrative Assistant ANGELA BRUBAKER, Senior Project Assistant MARY BETH MORRIS, Senior Project Assistant GREGORY NYCE, Senior Project Assistant
v COMMISSION ON GEOSCIENCES, ENVIRONMENT, AND RESOURCES M.GORDON WOLMAN (Chairman), The Johns Hopkins University, Baltimore, Maryland PATRICK R.ATKINS, Aluminum Company of America, Pittsburgh, Pennsylvania EDITH BROWN WEISS, Georgetown University Law Center, Washington, D.C. JAMES P.BRUCE, Canadian Climate Program Board, Ottawa, Ontario, Canada WILLIAM L.FISHER, University of Texas, Austin EDWARD A.FRIEMAN, Scripps Institution of Oceanography, La Jolla, California GEORGE M.HORNBERGER, University of Virginia, Charlottesville W.BARCLAY KAMB, California Institute of Technology, Pasadena PERRY L.MCCARTY, Stanford University, California S.GEORGE PHILANDER, Princeton University, New Jersey RAYMOND A.PRICE, Queen's University at Kingston, Ontario, Canada THOMAS A.SCHELLING, University of Maryland, College Park ELLEN SILBERGELD, Environmental Defense Fund, Washington, D.C. STEVEN M.STANLEY, The Johns Hopkins University, Baltimore, Maryland VICTORIA J.TSCHINKEL, Landers and Parsons, Tallahassee, Florida Staff STEPHEN RATTIEN, Executive Director STEPHEN D.PARKER, Associate Executive Director MORGAN GOPNIK, Assistant Executive Director JEANETTE SPOON, Administrative Officer SANDI FITZPATRICK, Administrative Associate
vi ACADEMIA DE LA INVESTIGACION CIENTIFICA, A.C. MAURICIO FORTES-BESPROSVANI, President JUAN RAMON DE LA FUENTE-RAMIREZ, Vice President LINDA MANZANILLA-NAIM, Secretary-Elect RUBEN BARRERA-PEREZ, Secretary SAUL VILLA-TREVIÃO, Treasurer ACADEMIA NACIONAL DE INGENIERIA, A.C. HECTOR NAVA-JAIMES, President LUIS ESTEVA-MARABOTO, Vice President CRISTINA VERDE-RODARTE, Secretary OCTAVIO MANERO-BRITO, Treasurer
PREFACE vii Preface Urbanization is a reality of our changing world. In developing countries, the lack of job opportunities in rural areas, decline in subsistence economies, and hope of a better life have given rise to the modern megalopolis. Unfortunately, urban infrastructure, institutions, and the natural resource base are often inadequate to support these burgeoning populations. A central question worldwide is, âhow can our cities be sustained under these circumstances?â Water, like air, is a vital resource without substitute. Its supply, allocation, and disposal present numerous challenges, all of which must be met to support these growing metropolitan regions. The Mexico City Metropolitan Area (MCMA) exemplifies these problems. The water requirements of the nearly 20 million residents present a formidable challenge to those responsible for providing water and wastewater services. As surface water within the Basin of Mexico is very limited, the principal water supply for the city is the Mexico City Aquifer, which is located beneath the metropolitan area. While the volume of water in storage is quite large, its quality is vulnerable to degradation from all of the activity above it. Lack of wastewater treatment and insufficient control over hazardous wastes have placed the aquifer and water distribution system at risk of microbiological and chemical contamination. Furthermore, the aquifer's use is restricted by problems of large- scale land subsidence. Since ground water exploitation first began in the last century, falling ground water levels have resulted in an average subsidence of 7.5 meters in downtown Mexico City. Subsidence has exacerbated
PREFACE viii the natural propensity of the city to flood and damaged the city's infrastructure. Attempts to control flooding and provide water and wastewater services in the MCMA have involved massive engineering projects, such as a deep drainage system and the importation of water from the Cutzamala Basin. The prevailing attitude among the population has been that water resources are state property and, as such, their use is a constitutional right (though not identified as such in the constitution) and free of charge. Traditionally, water supply and drainage services have been strongly subsidized by the federal government. The results have been severe financial deficits and waste of the resource through leakage and inefficiency of use. Rapid urban growth and insufficient finances have restricted the government's capacity to satisfy demands, extend the distribution system to areas with poor service, and provide adequate wastewater treatment prior to disposal or reuse. Since 1988, Mexico has initiated major reforms in water resource allocation and water services. Nevertheless, the future of water service in the MCMA, as in many other cities of the world, is uncertain. In a sense, this case presents an extreme scenario that could be faced in many other places. Because of the complexity of the problem and its relevance to other cities in Mexico and the world, a ground-breaking, binational study was jointly undertaken by the Mexico Academy of Science (Academia de la InvestigaciÃ³n CientÃfica, A.C.), the Mexico National Academy of Engineering (Academia Nacional de IngenierÃa, A.C.) and the National Research Council of the U.S. National Academy of Sciences and U.S. National Academy of Engineering. The partnership also involves the Mexico National Academy of Medicine (Academia Nacional de Medicina) and the U.S. Institute of Medicine. The study is part of a nongovernmental partnership to sustain and strengthen science and technology in both countries through collaborative activities. A part of this partnership is to undertake joint studies to illuminate significant public policy issues having scientific and technical underpinnings. To get started, a planning group of representatives from the various academies met in Cocoyoc, Mexico, in 1990âsponsored by the Tinker, MacArthur, and Rockefeller foundationsâand concluded that a study of the Mexico City Aquifer as a water supply source would be a timely and important undertaking. As the topic developed, participants determined that the study would provide greater value to local and regional decision makers if it evaluated the problems associated with water service in general. Therefore, the study scope was broadened to include the technical, social, economic, and institutional aspects of water service. In January 1992, a binational, multidisciplinary committee of volunteer experts was appointed by the academies of the United States and Mexico. The study was implemented with financial assistance from the Ford Foundation, Tinker Foundation, U.S. Environmental Protection Agency, United Nations Development Program, Mexico National Science
PREFACE ix Foundation (Consejo Nacional de Ciencia y TecnologÃa), Mexico Ministry of Health (SecretarÃa de Salud), and U.S. National Research Council. This bilingual report summarizes much of the information developed in the course of the study and serves to disseminate the results and recommendations to scientists, decision makers, and the interested public in both Mexico and the United States. It stands as the formal report of the study. A separate and more complete technical report in Spanish only is available from the Mexico National Academy of Engineering and the Mexico Academy of Science, and is referenced throughout this report. The separate Spanish report should be immediately useful to the technical, research, and planning communities in Mexico as they embark on the relatively new programs designed to improve the sustainability of water supplies in the MCMA. The committee conducted exhaustive investigations and deliberations over a 30-month period, including several formal meetings on both sides of the border, field visits, and collaborations among subsets of committee members. The committee members responsible for this report put forth considerable efforts, but they did not produce these significant products without assistance. First, the committee is indebted to a number of peopleâcollectively listed at the end of the report as âstudy associatesââwho volunteered their time, diverse expertise, and resources to the study. Their involvement enriched the reports and provided for a wider consensus in the resulting work. The committee and study associates went about their tasks with enthusiasm, friendly cooperation, and real affection for one another. As with all such reports produced through a committee effort, the success of the report is dependent on the skills, dedication, and energy of the staff assigned to the committee. The unique nature of this studyâthe first collaborative study to be carried out by the National Research Council and the science and engineering academies of Mexicoâdoubles the complexity of what is normally a very challenging effort. The committee was fortunate to have the services of National Research Council study director Gary Krauss, whose contributions throughout the study and report are extensive. In addition to his ability for overall management and his editorial skills, Gary was able to keep up the level of communication across borders and help resolve the technical and cultural issues that frequently confronted the committee. Special thanks are due as well to Project Assistant Gregory Nyce, who managed logistical arrangements for the committee and prepared the bilingual report manuscript for publication. On the side of the academies of Mexico, a small but very effective staff collaborated on the project. The contributions from the Mexico National Academy of Engineering study directors are particularly significant. The effective management and coordination of the early phases of the project by Alejandro Lozanoâwho is also a member of the Mexico National Academy of Engineeringâhelped individuals from diverse backgrounds and disciplines work together as a single committee. Julia Melchorâstudy director in the last phases
PREFACE x of the projectâeffectively managed the very difficult logistics of communications, committee meetings, and compiling the Spanish versions of the report. The coordination and supervision of project throughout its different stages were the responsibility of the committee co-chairs. The integration of information on water supply, distribution, drainage, quality, and institutions is no easy task for any large city. In Mexico, the data collected by federal, state, and local authorities for water management and planning are frequently disparate, rarely in a published form, and have not been collectively integrated or analyzed by the scientific community. The committee and others involved with this study believe that this effort represents the first attempt to present a more comprehensive framework for water supply in the MCMA1. In this regard, this study would not have been possible without the significant support and cooperation from the following government agencies, which provided critical staff time, information, and analysis: the divisions of urban services and water operation and construction of the Federal District (Departamento del Distrito Federal a travÃ©s de sus Direcciones Generales de ConstrucciÃ³n y OperaciÃ³n HidrÃ¡ulica y de Servicios Urbanos), the Valley of Mexico Regional Water Authority of the National Water Commission (ComisiÃ³n Nacional del Agua a travÃ©s de su Gerencia Regional de Aguas del Valle de MÃ©xico), the Water and Sanitation Commission of the State of Mexico (Gobierno del Estado de MÃ©xico a travÃ©s de la ComisiÃ³n Estatal de Agua y Saneamiento), the agencies for environmental health and epidemiology of the Ministry of Health (SecretarÃa de Salud a travÃ©s de sus Direcciones Generales de Saneamiento Ambiental y EpidemiologÃa), the National Ecology Institute of the Ministry of Social Development (SecretarÃa de Desarrollo Social a travÃ©s del Instituto Nacional de EcologÃa), the geophysics and engineering institutes and the Center for Ecology of the National University (la Universidad Nacional AutÃ³noma de MÃ©xico a travÃ©s de sus Institutos de GeofÃsica e IngenierÃa, y el Centro de EcologÃa), the Mexico School of Public Health (Escuela de Salud PÃºblica de MÃ©xico), and the recently created Federal District Water Commission (ComisiÃ³n de Aguas del Distrito Federal). While a study of this nature cannot identify specific designs and system details, it lays out concepts that should be pursued in the interest of a more sustainable water supply for the MCMA and for areas like it worldwide. Implementation will, of course, be quite difficult, especially where institutional and social policy changes are called for. Nonetheless, we hope that the concepts discussed in this report will be useful not only to decision makers, scientists, 1 It should be clarified that water resource data, especially concerning the quantity of water supplied to the MCMA, are rapidly changing. The data presented in this report are current as of approximately March 1994.
PREFACE xi and members of the public concerned with water resources specific to Mexico City, but also to others concerned with water resources management in regions where issues similar to those in Mexico City present themselves. When it comes to issues of resource allocation, environmental protection, and concern for humankind, there is indeed only one communityâthe world's human communityâthat shares the common goal of leaving this planet in no worse shape than it was in when we were born into it. Finally, we hope that this effort will foster the use of independent advice from Mexico's national scientific and engineering academies to improve the scientific and technological basis for resolving important public policy issues. CHARLES T.DUMARS and ISMAEL HERRERA-REVILLA, Co-Chairs Committee on the Mexico City Water Supply March 1995
xii 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. Bruce Alberts 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. Robert M. White 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. Kenneth I. Shine 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 Academyâs 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. Bruce Alberts and Dr. Robert M. White are chair and vice chair, respectively, of the National Research Council. The Mexico Academy of Science (Academia de la InvestigaciÃ³n CientÃfica, A.C.) was created in 1959 and is dedicated to organizing and promoting scientific investigations in all aspects of science. Dr. Mauricio Fortes is president of the Mexico Academy of Science. The Mexico National Academy of Engineering (Academia Nacional de IngenierÃa, A.C.) was created in 1974 to promote high quality engineering research, education, and technological development. Dr. HÃ©ctor Nava is the president of the Mexico National Academy of Engineering. www.national-academies.org
CONTENTS xiii Contents 1 OVERVIEW 1 2 THE MEXICO CITY METROPOLITAN AREA 4 3 DESCRIPTION OF THE MEXICO CITY AQUIFER AND ITS 8 EXPLOITATION Physical characteristics and hydrogeology Water level declines in the aquifer and land subsidence Water balance for the aquifer 4 WATER SUPPLY, DISTRIBUTION, AND DISPOSAL 19 Water supply and distribution Wastewater collection and disposal Water reuse and recycling 5 WATER QUALITY AND HEALTH CONCERNS 39 Vulnerability of the aquifer Monitoring and sanitary certification Quality of the water sources Water quality concerns in the distribution system Water-related health concerns 6 WATER DEMAND MANAGEMENT 53 Problems and priorities Water tariffs, use, and access in the MCMA Demand management tools Implementation issues 7 INSTITUTIONAL ISSUES 71 Water quantity institutions Water quality institutions 8 CONCLUSIONS AND RECOMMENDATIONS 78 REFERENCES 89 APPENDICES A Committee Member Biographies 99 B Study Affiliates 105
xv MEXICO CITY'S WATER SUPPLY Improving the Outlook for Sustainability