Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 78
Mexico City’s Water Supply: Improving the Outlook for Sustainability 8 Conclusions and Recommendations As the cultural, economic, and industrial center for the nation, Mexico City has been a magnet for continued and often uncontrolled urban growth. A history of federally subsidized water service and poor financing, while encouraging economic development, has limited the capacity of the government to expand the network, treat water and wastewater, and fund repairs. Recently, the Mexican authorities have moved toward more efficient management of the region’s water supply resources. Reversing past trends and implanting the new conservation strategies will be difficult. The challenge for decision makers in Mexico City will be to balance the need for obtaining new sources of water with more careful management of existing sources. Thus, more attention should be given to managing water demand through pricing mechanisms, education, and conservation and reuse programs. There are several general recommendations of a diverse nature concerning improved understanding of the regional hydrology, reuse of reclaimed wastewater, protection of the quality of existing resources, greater efficiency of use, and institutional change, all designed to improve the existing system. The issues and related recommendations presented below are meant to guide policy makers attempting to improve the quantity and quality of water resources in the Mexico City Metropolitan Area (MCMA). The recommendations are not in any order of priority, but should all be pursued with vigor, certainly before any further source development is considered. Successful implementation of these concepts should enhance the sustainability of Mexico City’s water supply for many decades—and that is where priorities should be placed.
OCR for page 79
Mexico City’s Water Supply: Improving the Outlook for Sustainability ISSUE: CONTINUED USE OF THE MEXICO CITY AQUIFER While the quantity of ground water in storage in the southern portion of the Basin of Mexico is estimated at 240 to 350 times the current annual draw down, a usable life of the Mexico City Aquifer can not be predicted with reliability. Over-exploitation continues to cause subsidence problems and increase the vulnerability of the aquifer to contamination. Limited information is available concerning geological and chemical properties of the aquifer at depths greater than those of current pumping. The hydrogeology of the southern portion of the Basin of Mexico, occupied by the MCMA, is best understood. To the north of Sierra Guadelupe, less is known concerning the quality and availability of ground water reserves. Even so, previous studies in the southern part of the basin have suffered from a lack of continuity and compatibility. Data used in current prediction models for the Mexico City Aquifer are not reliable, and the consequences of a prediction error on long-term planning may be severe. More complete information on the draw down rates of the aquifer, the relevant hydrologic parameters, vulnerability to contamination, and an identification of the critical water levels below which continued pumping would no longer be efficient would be required to predict the aquifer life more reliably. Further, the development of appropriate rates of ground water withdrawal should also be based on social factors, the economics of water resource development and distribution, the influence of conservation and demand-management measures, and public policy. Although this study has not examined important issues in regional and urban development, it is clear that water resources planning and the collection of data should anticipate the rates and impacts of growth, not only in the MCMA, but in the entire Basin of Mexico, and adjoining basins. Recommendation: A long-term research program for determining the hydrologic, physical, chemical, and biological characteristics of the aquifers in the Basin of Mexico should be developed. A coordinated, long-term research program should be implemented to support sustainable management of the aquifer system throughout the Basin of Mexico. The program should emphasize continuity among studies and should be directed by an advisory board with technical representatives from all affected parties having jurisdiction within the area. This program should involve all the institutions that regulate water from the Basin of Mexico aquifers, thus bringing different perspectives to the table including environmental, developmental, health, cultural, and scientific interests. The long-term study should examine the thickness, extent, and depth of the aquifers. The study should determine more reliable estimates of porosity, permeability, storativity, and hydraulic conductivity of the aquifers. Other important components include (1) changes in water quality with depth, geographic
OCR for page 80
Mexico City’s Water Supply: Improving the Outlook for Sustainability location, and relation to producing well fields, (2) the degree of connectivity between the various zones within the aquifers and in the recharge zones, (3) the extent and location of faults or other compartmentalizing factors within the aquifers important for optimizing well placement, and (4) physical, chemical and biological characterization of the aquifers. These studies must be carried out with the best available scientific approaches and should include a system of monitoring wells, use of remote sensing and aerial photography to map and fully understand zones of recharge and the consequences of subsidence, and development of a geographic information system to integrate surface features, infrastructure, and hazardous activities on a common base map. Recommendation: The optimal yield for the Mexico City Aquifer should be determined. After the characteristics of the Mexico City Aquifer are understood with some level of confidence, an interagency and interdisciplinary panel should be brought together to determine an optimum yield for the aquifer on the basis of an evaluation of multiple objectives. It may be useful to engage in this analysis the same advisory board that would be directing the long-term ground water research program for the Basin of Mexico. What is optimal for the Mexico City Aquifer will depend, at a minimum, upon a number of interrelated factors: a consideration of the economic dependence of the region on the ground water resource, the consideration of deteriorating water quality with increasing aquifer depth, the current impacts of point source and nonpoint source pollution, the availability and actual marginal cost of obtaining and distributing other new sources of water, an analysis of water use, the influence and potential of programs for water pricing and metering, water conservation, water reuse, and ground water recharge, the impact of water use on other environmental interests, and the best calculations available as to the potential long-term life of the aquifer at the various rates of pumping based on the considerations above. ISSUE: IMPLEMENTATION OF WATER REUSE PROJECTS Wastewater discharge from the MCMA is estimated at 44.4 cubic meters per second, or 74 percent of the total water usage. Most of the wastewater exits the Basin of Mexico. Consequently, there is a very large potential for the fur-
OCR for page 81
Mexico City’s Water Supply: Improving the Outlook for Sustainability ther development of water reuse programs to conserve existing water supplies for higher quality uses. Limited water reuse programs have been initiated in the MCMA within the last few years, including programs on aquifer recharge with storm water and reclaimed municipal wastewater, and industrial reuse and recycling of reclaimed wastewater. While some types of industrial reuse, such as cooling water for electric generator plants, can be accomplished without excessive treatment, the majority of water reuse activities will require some level of treatment (to reduce pathogens and other undesirable contaminants). In the Federal District, industrial pretreatment of wastewater has been mandated by a 1990 law; however, little is known about the effectiveness of the program. Recommendation: Reclaimed, treated municipal wastewater has great potential and should be used increasingly as a source of water for urban and industrial uses including landscape irrigation, agricultural irrigation, and aquifer recharge. The use and degree of treatment of reclaimed, treated wastewater should be targeted for specific areas and purposes in the MCMA. Feasibility studies for agricultural and industrial reuse should continue. Another possibility would be to provide new urban development with the necessary infrastructure (e.g., dual distribution systems and low flow plumbing) for using reclaimed water (e.g., for toilet flushing and air-conditioning in high-rise buildings, and for landscape irrigation). These measures, when taken during the construction stage, are more economical than when they have to be retrofitted. Implementation of industrial pretreatment programs will be necessary for effective wastewater treatment, and will be a prerequisite for developing a viable ground water recharge program and other water reclamation projects. If water reuse programs are to be safe and effective, all municipal wastewater should receive proper treatment prior to disposal, as well as for reuse purposes. ISSUE: VULNERABILITY OF GROUND WATER TO CONTAMINATION Unlined garbage dumps, damaged sewer lines, untreated domestic and industrial water, lack of control of hazardous materials, and other human activities all leave the aquifer vulnerable to contamination. The transition and mountain zones are particularly vulnerable because of the high recharge rates in these areas. The lacustrine zone, previously considered to be an impermeable clay layer under the MCMA, is likewise vulnerable because of recent findings that suggest the downward movement of contaminants may occur in this region as well. Recommendation: An orderly, comprehensive ground water monitoring and protection program should be implemented. Such a program should
OCR for page 82
Mexico City’s Water Supply: Improving the Outlook for Sustainability include the identification and mapping of vulnerable areas in the MCMA, the types of human settlements that occur, location of active production wells, location of abandoned wells, the type of sewer services provided, the industries in the area, the extent of industrial and domestic wastewater treatment employed, and an identification of other activities that contribute to ground water contamination. The evaluation of the impact of these activities on nearby production wells should be the highest priority. Experience has shown many times that investments in ground water resource protection are more effective and efficient than site remediation. Indeed, after a site is contaminated, it is not always feasible to restore it to drinking water standards. Options to protect the water supply may include increased restrictions on industrial discharges, measures to contain hazardous waste, installation of water and sewer services where they are lacking, the implementation of wellhead protection programs, or closing and relocating of wells. Further research is needed in the areas of the transition and lacustrine zones to characterize more accurately the vulnerability of the aquifer. ISSUE: HUMAN HEALTH CONCERNS FROM PATHOGENS The potable water distribution system is vulnerable to contamination by pathogens. Studies indicate the presence of pathogenic organisms in water samples from home taps, domestic cisterns, and other parts of the system, although available studies do not pinpoint the source of the problem. The water distribution system is old and has suffered extensive leaks, partly through the effects of land subsidence. Leaks, combined with system interruptions and periods of lower pressure, make the system susceptible to infiltration of contaminants from the subsoil, which may be contaminated by leaking sewers, septic tank discharges, and leakage and overflow from drainage canals. Much of the sewer system consists of unlined open canals and drainage ditches. None of the wastewater from the MCMA is treated prior to disposal (the 10 percent that is treated goes toward reuse projects). Therefore, largely untreated sewage flows through these open canals, creating a situation of potential high human exposure to pathogens and parasites and consequent risk of disease. Another concern is the location of certain drinking wells in areas adjacent to sewage canals. Infectious intestinal diseases, especially acute diarrhea, are a leading cause of infant mortality in the MCMA. Increased use of oral rehydration has contributed to the decline of deaths from these diseases in Mexico over the past several years, although oral rehydration does nothing to address the cause of the infections, such as exposure to contaminated water.
OCR for page 83
Mexico City’s Water Supply: Improving the Outlook for Sustainability Recommendation: Wastewater treatment prior to disposal and increased surveillance of public health and the water distribution system should be high priorities. Existing wastewater treatment plants should be expanded and upgraded to handle larger volumes of wastewater, and attention should be placed on wastewater treatment for disposal purposes. Priority should be given to areas with relatively high rates of infectious intestinal diseases. A monitoring program should be developed to collect the appropriate data and perform the necessary epidemiological studies in order to trace the source of the problems, whether they be in the water distribution system, the household, the neighborhood, or from raw water sources. Increased monitoring may also be necessary at bottled-water plants and at public swimming pools. The water distribution system should maintain a continuous, adequate pressure and residual level of disinfectant. ISSUE: REGULATION AND MONITORING OF WATER QUALITY The quality of water in Mexico is determined presently by a triumvirate of powerful institutions: the Secretary of Social Economic Development, the Secretary of Health, and the National Water Commission. To date, there have been difficulties establishing a broad set of water-quality standards to comply with the 1992 Law of Norms and Monitoring. Conflicting mandates among the agencies may make it difficult to set the pollutant priorities and implement a program for reducing pollution in the water supply. There is concern about the data collection and record-keeping capabilities of the Central Water Quality Laboratory of the Federal District. The laboratory must cover an enormous service area (approximately 667 square kilometers) with high urban density and extensive industrial development. The great complexity of the water distribution network suggests diverse water quality conditions in different parts of the network. The State of Mexico has less capability than the Federal District to monitor and report on water quality within its metropolitan service area. Water quality information is not readily available for either service area. Recommendation: The Federal District and the State of Mexico should work together to improve the capabilities for water quality data collection, information storage, and reporting of monitoring results. Current and reliable information should be available to the general public as well as government and research institutions. The information should be at a suitable level of detail to identify what parameters may be out of compliance in specific areas of the distribution system, and its significance to public health.
OCR for page 84
Mexico City’s Water Supply: Improving the Outlook for Sustainability ISSUE: ADEQUACY OF WATER MANAGEMENT AND PLANNING STRATEGIES. Water costs in the MCMA have escalated dramatically, and existing revenues do not come close to paying the marginal costs of operation and maintenance. This imbalance restricts the ability to expand the network to underserved areas, treat sewage, and fund the repairs of leaks in the distribution system. The actual scarcity and value of water is not reflected in its administration or consumption. Most use is unreliably metered or not monitored at all, and a majority of water bills go unpaid. Neither actual water use nor uncollected revenues are known with any precision. Water demand and supply can be brought more into balance by promoting a broader notion of management in which both supply and water use receive attention in the planning process. Water use can, in many instances, be reduced without impinging on the economic development of the region by substituting conservation for an increase in water-supply capacity. Specific policy tools include educational programs, plumbing retrofit programs, conservation audit programs, conservation laws, meter installation and maintenance programs, urban land-use planning, and pricing structures aimed at bringing user costs more in line with supply costs. Recommendation: Functioning meters should be installed for all but the poorest consumers. To achieve such metering, several million additional meters would have to be installed, at a cost of roughly $100 each. While this is a large sum of money, it is small in comparison with the amounts required for infrastructure repair and upgrading, or the importation of new water sources from distant basins. If coupled with price restructuring, metering would help the local governments meet their water-system costs fully and fairly. Metering water use, monitoring the reading of meters, repairing broken meters, and revising water rates are essential to water conservation and should be pursued together. The highest priority should go to metering large users who are most well off. Less is gained by metering the poorest and smallest users, many of whom do not even have access to water within their dwellings. Recommendation: A reliable method of meter reading and bill collection should be established, and water tariffs should be set at a level that allows each water authority to develop a self-sustaining program. Realistic water pricing is one of the most fundamental keys to water-demand management. Tariff setting should be a multi-objective tool to influence consumption, satisfy financial goals, and achieve important environmental and social goals. Moreover, sustainable and efficient water use is most likely to occur when municipal water utilities are financially self-sufficient, and users pay approximately the true cost of water development, distribution, and systems mainte-
OCR for page 85
Mexico City’s Water Supply: Improving the Outlook for Sustainability nance. The marginal cost of water, including treatment and disposal costs, should be established and used as a guide for developing water rates. An increasing block tariff structure, with provision for very low rates for very small amounts, is a practical means for doing so. The capacity of the public utility—whether government or privately owned—should be enhanced to update connection records, read meters, prepare the bills, and sanction nonpayers, all of which will require training a cadre of people with the requisite skills. The development of an accounting database of water users (starting with the major water users) will facilitate the implementation of this policy. Recommendation: The water service infrastructure should be adequately repaired, maintained, and extended. The Federal District has embarked on an agressive campaign to eliminate system leaks, which is perhaps as important to water supply as the development of an entirely new source, and this program should be encouraged. Additionally, aging infrastructure and failing installations should be replaced. Although difficult to accomplish, adequate water service must be provided to all households within designated service areas. ISSUE: ORGANIZATIONAL OPPORTUNITIES AND CHANGE Managers, administrators, and politicians have a central role in promoting sound water-pricing practices, research and development, public education, and other regulatory policies, including an examination of the potential benefits of privatization. Governments have a difficult time dealing with water conservation because water is a highly-charged political subject. Many people in Mexico believe that, because water is essential to life, authorities are obliged to bring it to the population at little or no cost. Therefore, education and public awareness have important roles to play in conservation. A well-designed public education program can change the water-use habits of a community and may, as a result, achieve a substantial reduction in water demand. Public conservation campaigns have been initiated by the Federal District; however, their effectiveness has yet to be evaluated. The Federal District is embarking on a privatization initiative, motivated both by the belief that the private sector has the potential for improved managerial efficiency via the profit motive. The initiative leaves infrastructure ownership and capital investment in the hands of the public sector, but will gradually contract out many management functions to private firms via short term competitive contracts. This transition to private management will be a radical shift for both the government and the public.
OCR for page 86
Mexico City’s Water Supply: Improving the Outlook for Sustainability Recommendation: Public education campaigns must be developed, maintained, and evaluated. It is important to promote conservation among the general public and to target the message appropriately. Little emphasis need be placed on targeting those who do not have in-house or on-site access, since they do not use much water and have little control over its use. Opportunities for involving the private sector in public education as well as in the management responsibilities of water utilities should be explored. Recommendation: Professionals in the social science disciplines should be recruited into the water regulatory and management agencies to help develop demand management programs. One of the principal impediments to improved water demand management is the inability of agency officials to perform adequately the tasks required. The past emphasis upon construction of new water-supply facilities is reflected in the recruitment and promotion of agency officials who have engineering expertise but are not skilled in psychology, public information, public policy, and economics. The past emphasis on the physical aspects of the water system has de-emphasized the collection of necessary information about the characteristics of water users, their practices, and likely incentives to reduce demand. Even though the management of the water distribution system will be privatized, municipal agencies still have a major role to play in setting and overseeing water policy. Therefore, a concerted effort to build the capacity of water management agencies is required, particularly in the recruitment and promotion of professionals with skills in social science disciplines such as psychology, public information, public policy, and economics. Water conservation and demand management offices should be hierarchically positioned within water supply agencies so that they can exert authority in overall decision making. ISSUE: EQUITY Residents of the MCMA receive diverse levels of water service and use very different quantities of water. Water is readily available at low cost to some, while water service is undependable and/or inconvenient to others. The emphasis upon water conservation and demand management should not obscure the need to upgrade water service to a substantial number of the poorest residents. Water agencies will need widespread public support as they attempt to institute rate structure and other reforms. Such support will not be forthcoming unless there is a perception that service is distributed equitably. The poor in many developing countries do not have household access to the public water system, and consequently they tend to pay a larger portion of their income to obtain good quality water than those who are better off and who have both better access and low water rates (Crane, 1994, World Bank, 1992, Whittington and Choe, 1992). The putative effects on the poor are not an impediment to
OCR for page 87
Mexico City’s Water Supply: Improving the Outlook for Sustainability rational rate structures. Further studies are warranted to provide a fuller understanding of how expansions in the distribution system, as well as water-tariff policies, affect the health and financial status of the very poor. Additionally, intergenerational equity should be of concern. If the demand for water cannot be sustained over the long term, future generations of MCMA residents will have even more limited access to potable water. Recommendation: Dependable water services should continue to be extended to the poor. The poorest segments of the MCMA population do not have a convenient, dependable water supply. In evaluating who benefits and who pays as a result of reforms such as rate restructuring and privatization, particular attention must be paid to the impact on this segment of the population. Water is a basic commodity, essential to human health and welfare, and sufficient access to serve human needs should be available to those with low as well as high incomes. Increasing the block rates of nonmetered high-volume users will shift some of the cost burden to those most able to afford it, as well as encourage water-conservation measures. Recommendation: The public should be involved in decisions concerning privatization and water demand management. As water moves from a free natural right to a commodity for which one pays money, those who pay will ultimately demand and are entitled to a voice. It is important to assure the public that the price of the good is reasonable in relation to its cost, that the quantity and quality of water is distributed fairly to all users, and that conservation programs and use of subsidies are equitable. Therefore, the public should have formal avenues to offer their opinion and to be involved in the decision process.
OCR for page 88
Mexico City’s Water Supply: Improving the Outlook for Sustainability This page intentionally left blank.
Representative terms from entire chapter: