IDL-11078.Pdf
Total Page：16
File Type：pdf, Size：1020Kb
Thirsty Cities Some major cities of Latin America and the Caribbean. Cities discussed in detail are shown in bold type. Thirsty Cities Urban Environments and Water Supply in Latin America Danilo J. Anton INTERNATIONAL DEVELOPMENT RESEARCH CENTRE Ottawa Cairo Dakar Johannesburg Montevideo Nairobi New Delhi Singapore © International Development Research Centre 1993 PO Box 8500, Ottawa, ON, Canada K1G 3H9 Anton, D. Thirsty cities: urban environments and water supply in Latin America. Ottawa, Ont., IDRC, 1993. iv + 197 p.: ill. /Water supply/, /water resources/, /water management/, /urban environment/, /environmental management/, /towns/, /Latin America/, /Caribbean/ /environmental degradation/, /environmental policy/, /river basins/, /groundwater/, /surface water/, /hydrology/, /sustainable development/, /case studies/, references. UDC: 628.1(8 21) ISBN: 0 88936 666 7 A microfiche edition is available. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, or otherwise, without prior permission of the International Development Research Centre. Contents 1. Introduction 1 2. The Latin American environment 9 Physical environment 9 Geology and geomorphology of urban sites 11 Socioeconomic environment 19 3. Environmental degradation and inadequate policies 23 Main environmental issues affecting the LAC region 24 Halting current trends and managing the environment 26 Environmental policies for the region 27 Approaches to policy formulation 31 4. Hydrological basins 35 Surface water 35 Anthropogenic impact on hydrographic basins 36 Hydrographic basins as management units 36 5. Groundwater sources 41 Suitability of groundwater reservoirs 41 Aquifers suitable for groundwater use 44 6. Cities depending on surface water 61 São Paulo metropolitan region 61 Montevideo and southern Uruguay 66 Water supply and environment in the sabana of Bogotá70 Santiago de Chile 75 7. Cities depending on both surface and underground water 79 Greater Buenos Aires and La Plata 79 The Cochabamba valley 84 The aquifer at Lima 88 Santa Marta on the Caribbean coast 93 Recife and the Pernambucan lowlands 96 San José in the central valley of Costa Rica 100 8. Cities depending mainly on groundwater 103 The valley of Mexico 103 The valley of Guatemala 110 The Managua basin 113 The capital of the Mayan nation: Mérida of Yucatán 119 9. Management of water resources 121 Complexity of water management in urban areas 121 Environmental problems and their costs 122 Causes of water supply problems in urban areas 130 10. Sustainable development of water systems 139 Factors affecting demand for water 139 Level of demand in Latin American cities 141 Water resources and the use of wastewater 142 Economic analysis 144 11. Quenching the urban thirst 147 Water and poverty 147 Water, health, and quality of life 147 Scarcity of water 148 The demand side of the equation 149 Sustainability and equity 149 Unsustainable models in the LAC region 150 Conclusions 150 References and Bibliography 155 Glossary 167 1 Introduction One of the main features of the recent historic and geographic evolution of Latin America and the Caribbean (LAC) has been a concentration of the population in urban areas. The urban population of the region is estimated to be increasing at the rate of 3.6% per year (Bartone 1990). At the end of the 1980s, there were over 280 cities of more than 100 000 inhabitants; the 210 million people in these cities represented about 46% of the region s population. About 25% of these cities have populations above 0.5 million people, constituting 35% of the total population. Extremely high concentrations occur in the 13 largest urban centres, whose populations exceed 3 million (Table 1). The total population of these metropolises is 105 million or 23% of the total for Latin America and the Caribbean. It is difficult to provide accurate or comparable figures for the populations of metropolitan areas. Large cities often encroach beyond their municipal or provincial boundaries. Other cities, formerly separated, may merge into the main urban area. Equally, the rate of annual urban growth for any growing city is hard to define, because the census units may become noncomparable during the intercensal period (i.e., because satellite cities are incorporated). I have tried to surmount these difficulties using different sources for some cities that appeared clearly uncomparable1 in some data sources. Population growth projections are only indicative. In all cases, an average population growth for the period was estimated based on the growth of the last intercensal period and this figure was cumulatively applied for the projected period. I could not apply the same criteria for all cities but, in some obvious cases, corrections were made. 1 In some cities, the problems are almost insurmountable. It is difficult to decide if Campinas, São Jose dos Campos, or Santos belong to the metropolitan area of São Paulo. This Brazilian city is growing through the Paraiba Valley along the Via Dutra Highway toward Rio de Janeiro: some people are already forecasting a megacity to be called São-Rio. A similar problem occurs in Mexico City because of the merging of some large, formerly independent, urban areas (i.e., Toluca, Cuemavaca, Puebla, Querétaro, and Cuautla). In the last censal survey, growth of Mexico City appeared somewhat curtailed if only the Valley of Mexico is considered, but if the other cities listed are included, the growth is even further accelerated. In the table, I have tried to conciliate statistical data (often not reflecting reality) with the actual ground truth. Table 1. Current and projected populations (millions) for some major cities of the LAC region. Note: na = not available. Sources: 1 Wilkie et al. (1988); 2 Abril (1993); 3 Europa (1991). The largest cities have experienced the greatest increases, and demographic statistics leave little hope of any dramatic reversal of present trends. If the rate of growth is not significantly reduced, by the year 2020, more than 500 million inhabitants of Latin America (or two-thirds of its population) will be living in cities of over 100 000 people. Overconcentration has reached alarming levels in three megacities: Ciudad de México (19.5 million), São Paulo (16.5 million), and Buenos Aires (12.2 million). Forecasters predict that the populations of Mexico City and São Paulo will soar to 25 and 22 million, respectively, well before the year 2010. By that time, several other cities will exceed 10 million, including Rio de Janeiro (12 million) and Lima (10 million) and many more will exceed or approach 5 million (Belo Horizonte, Bogotá, Caracas, Guadalajara, Monterrey, Pôrto Alegre, Recife, Salvador, and Santiago). This degree of urban concentration is much higher than that expected in cities of developed countries, whose growth is slower. These populations are also higher than expected for the largest megacities of the most densely populated countries in the Third World. The People s Republic of China, with a population of over 1.1 billion, does not contain any city with more than 15 million people: Shanghai, the largest city in China has only 12 million. São Paulo and Mexico City are larger, in spite of the much smaller populations of their countries (14 and 9 times smaller, respectively). In India, with a population of 800 million, the two largest cities Calcutta (15 million) and Bombay (14 million) also have populations considerably smaller than the two largest LAC megalopolises. This uncontrolled growth of LAC urban areas has occurred at the same time as one of the worst financial crises of the region s history. In almost all LAC countries, foreign debt has increased at an even faster pace than the growth of their urban populations. This problem became particularly acute at the end of the I980s in Brazil (foreign debt at that time of US$116.9 billion), Mexico (US$105.6 billion), and Argentina (US$S6.2 billion), but is also found in many smaller countries. In some cases, lack of resources prevented even the payment of interest on these debts over a relatively long period (e.g., Peru and Argentina in 1988 1989). In other countries, net transfers of resources as a result of profit repatriation and debt servicing or payment have also depleted available funds in public coffers and have jeopardized the acquisition of new credit. Little (if any) new money has been available for investment in infrastructure of any magnitude at a time when such investment is most needed to provide the necessary services for the booming urban population. One of the public services most affected is urban water supply. Historically, Latin American cities have relied on their closest sources of water, which in most cases were freshwater streams, lakes, or springs. Soon, these resources were exhausted or degraded, and the cities were forced to invest considerable funds in the construction of dams and pipelines to bring water from more remote sources. Continually expanding cities have outgrown most water-supply systems, and new sources must be tapped to satisfy the needs of their populations. However, funds are not available. Few new reservoirs are being built and few pipelines are being installed. In fact, expansion of the systems has been almost completely halted. Less water is available per person and this situation is gradually becoming worse. In addition, distribution systems (originally designed for much smaller populations and for limited use) are becoming not only inadequate, but also obsolete they increasingly require repairs at a time when less money is available to carry them out. As a result, the amount of leakage is increasing, augmenting water consumption from the systems. Breakages (and subsequent water losses) are common, with frequent drops in pressure increasing the risk of contamination of waterlines. Old reservoirs are also decaying. Their storage capacity is decreasing due to silting, watershed basins are being invaded by urban and rural dwellers, and uncontrolled industrial activity is producing changes both in hydrological regime and water quality.