Improving groundwater management: Mexico

Transcription

1 7 Improving groundwater management: Mexico GENERAL INFORMATION Implementing institution: Instituto de Geofísica, Universidad Nacional Autónoma de México (UNAM) Head: Jaime Urrutia Fucugauchi Details of institution: Address: Instituto de Geofísica, Universidad Nacional Autónoma de México, Cd. Universitaria, México, D.F., México CP Tel.: (+52) Fax: (+52) Web site: Implementation period: 1986-present. 87

2 88 V OLUME 11: SAFE D RINKING WATER Costs: Total cost to date is US$460,000, including US$70,000 provided by the Consejo Nacional de Ciencia y Tecnología (CONACyT), the federal agency that funds scientific research in Mexico, used to buy geophysical and computer equipment and to carry out field research; US$260,000 provided by the Universidad Nacional Autónoma de México (UNAM), used to cover student fellowships, to purchase hydrogeological field equipment and for travel to field sites; US$30,000 from Grupo Xcaret (private sector) used to develop a monitoring system for the Yucatan aquifer; and an estimated US$100,000 from the Quintana Roo Speleological Survey to cover the costs of exploration. S UMMARY Drinking water in Mexico s Yucatan Peninsula is obtained from a thin lens of fresh groundwater that floats above denser, saline water. Currently, the disposal of waste water is carried out by injecting usually untreated but sometimes treated water tens of metres below the fresh/salt water interface in this aquifer. Thus, the only source of drinking water on the peninsula is also the recipient of both municipal and industrial waste. Scientists from the Instituto de Geofísica of the Universidad Nacional Autónoma de México (UNAM) have been carrying out a hydrogeological characterization of the aquifer. Municipal, State and federal government officials are now beginning to recognize the importance of this work. To date, the available hydrogeological, geochemical and geophysical data for northwest Yucatan have been analysed and it has been proposed that a hydrogeological reserve zone be established for Merida, the largest city on the peninsula. B ACKROUND AND J USTIFACTION The Yucatan Peninsula (fig. 1) is made of limestones and evaporates, a type of sedimentary rock formed by the evaporation of seawater. As a result of the dissolution of the calcium carbonate in the limestone, a mature karstic system of caves and potholes exists throughout the peninsula. To date, more than 500 kilometres of subaquatic cave systems have been mapped in the area, and the mapping efforts continue to this day (fig. 2). For example, more than 130 kilometres of underground passageways in the Ox Bel-Ha system, located in southeastern Yucatan, have been mapped, making it the largest subaquatic cave system in the world. Here it is possible for a diver to enter a cenote or sinkhole nine kilometres from the coast and emerge at sea without ever seeing daylight.

3 Improving groundwater management: Mexico 89 Figure 1. Location of the Yucatan Peninsula, the area covered by this case study. Figure 2. Cenote Maya Blue, a subterranean cave system mapped by the Quintana Roo Speleological Survey. However, owing to the nature of these rocks, very little soil has formed. The lack of soil cover means that the aquifer within the karst is a thin, freshwater lens that floats on top of saline water. Beneath Merida, the largest city on the peninsula with a population of some 600,000, the freshwater lens is just 60 metres thick. The porous nature of the limestone rock also means that saltwater has been found more than 110 kilometres from the coast. This means that the aquifer is both the source of the region s drinking water as well as the recipient of its domestic and industrial liquid waste. Also, as a result of these large conduits, any contaminants that reach the water table can quickly be transported elsewhere, eventually reaching the sea. Contamination of this fragile groundwater system with metals, organic and inorganic compounds and biological materials has been documented in different areas of northwest Yucatan. Related to this, a major threat to the health of the inhabitants of northwest Yucatan, in particular those living in Merida and between Merida and the coast (or downgradient from Merida), is the lack of a municipal sewage collection and treatment system. Pathogens transported by groundwater continue to be the leading cause of death for children under five years old. Another issue of concern is that reports published or made available by the National Water Commission, the federal agency in charge of water, do not receive any external review and very often no internal review either. However, these reports are still taken to be the official reports on which many regulations are based. Critics in academia have suggested to the National Water Commission that the information be ranked as it is commonly done in academia: the primary source is international peer-reviewed literature, followed by

4 90 V OLUME 11: SAFE D RINKING WATER Mexican peer-reviewed literature, and finally non-peer-reviewed literature such as theses, environmental impact statements and technical reports. Another threat to the eastern part of the Yucatan Peninsula is the rapid growth of the tourist industry. Although the Government is trying to regulate its expansion, the reality is that little planning is taking place. Currently, there are approximately 80,000 hotel rooms on the Riviera Maya. Estimates suggest that between 10 and 18 support personnel are needed per hotel room, taking into account the hotel support staff as well as the indirect support staff (local mechanics, staff at the supermarket, etc.). However, no estimates of the carrying capacity of the area in terms of the number of hotel rooms that the area can accommodate in a sustainable fashion have been made. Thus, although the area is developing fast, basic information with regards to groundwater and other environmental issues is missing. The thickness of the freshwater lens beneath the area is unknown as is the nature of the fresh/salt-water interface, the direction and velocity of groundwater flow and the spatial distribution of groundwater quality. While the hotels and tourist resorts have installed modern water purification and water treatment facilities, the settlements that have grown up in support of these facilities lack such basic necessities as piped potable water or sewage collection and treatment systems. As a result, local inhabitants often drill a shallow well (in this area, the water table is less than six metres deep) and dispose of their domestic waste by either dumping it into available cenotes or excavating a shallow borehole into which the waste is pumped. Thus, there is reason to suspect that groundwater, especially in the larger cities, is carrying a significant bacteriological burden (fig. 3). The collection and disposal of solid waste constitute another issue affecting water quality. Currently, abandoned quarries are used as sanitary landfills. Again, this practice is not a healthy one. Figure 3. Schematic diagram showing freshwater flowing out to sea, saltwater flowing inland, and deep (approximately 50 metres below the land surface) disposal of untreated sewage. The presence of vertical conduits could allow treated water to migrate upwards into the freshwater lens (after Meacham, 2000).

5 Improving groundwater management: Mexico 91 What is needed is a master plan for the Yucatan Peninsula that considers at least three issues required to achieve the sustainable development of the area: provision of safe drinking water to the inhabitants; development of a waste collection and treatment system; and development of a solid waste collection and disposal programme. Achieving these goals will require scientific studies to estimate the true extent of the groundwater resources of the peninsula and the development of a map of the extensive subaquatic cave systems, as these are preferred flow paths for any contaminants. D ESCRIPTION To date, five hydrogeologists working in Mexico have conducted their field research in the Yucatan Peninsula. Scientists at the Instituto de Geofísica of the Universidad Nacional Autónoma de México (UNAM), for example, have been conducting hydrogeological research in the area since This research group has also established strong connections both with other national and international research groups that continue to conduct hydrogeological research in the Yucatan. As a result, the groundwater systems of the Yucatan Peninsula are the best-characterized aquifers in Mexico. More recently, contact with non-governmental organizations (NGOs), such as Amigos de Sian Ka an, and a commercial ecotourism company, Grupo Xcaret, that began with an informal exchange of information has developed into a collaborative project to develop a sustainable groundwater management plan for the Yucatan Peninsula that will ensure the provision of safe drinking water for the inhabitants for generations to come. A strong network has been established between the three main organizations, UNAM, Amigos de Sian Ka an and Grupo Xcaret, with the goal of educating the public, government officials and members of the business community. To this end, network members participate in radio shows, give interviews to the press and continuously lobby local and State government officials. The network also organizes both high- and low-level meetings. For example, in collaboration with the United States-based NGO, The Nature Conservancy, Amigos de Sian Ka an convened a meeting to pool all of the hydrogeological information on the Yucatan Peninsula. In 2004, the Mexican Academy of Sciences held a joint workshop with the United States National Academy of Sciences attended by high-level federal, State and municipal policy-makers. These combined efforts have increased the recognition of the groun water problem, particularly in government circles. A major outcome of this collaborative research has been the proposal, developed in 2000, to establish a hydrogeological reserve zone for the city of Merida (fig. 4).

6 92 V OLUME 11: SAFE D RINKING WATER Figure 4. Hydrogeological reserve zone proposed for the city of Merida, Yucatan, Mexico. P ATENTING AND C OMMERCIALIZATION No patents have been developed during the work outlined in this case study. However, the development of a sustainable water management plan for the Yucatan area should help the long-term development of the local tourism industry, thus providing employment and development opportunities for the local communities. P ARTNERSHIPS The core group involved in this case study, UNAM, Amigos de Sian Ka an and Grupo Xcaret, is now trying to expand the network by reaching out to other NGOs, other academic institutions (located primarily throughout the Yucatan Peninsula) and local and State planning agencies. Other regional and international collaborators include the Division of Water Sciences of UNESCO, the Mexican Academy of Sciences, the National Ground Water Association (United States), and Northern Illinois University (United States). R EPLICABILITY The mapping of aquifers and subterranean cave systems is now being carried out in other regions of Mexico. The methodology proposed for the establishment of a hydrogeological reserve zone for the city of Merida is also now being used in other parts of Mexico. Similar karstic aquifer systems are present in many parts of the world, including many Caribbean islands and countries bordering the Mediterranean areas. Therefore, with minor modifications, the method proposed to protect the groundwater of Merida can easily be applied elsewhere. P OLICY I MPLICATIONS The development of the proposal for a groundwater protection zone around Merida has meant that the joint efforts of academia, private industry and an NGO

7 Improving groundwater management: Mexico 93 are helping to change the water management practices implemented by both State and municipal policy-makers. The research and awareness-raising campaign outlined in this case study now mean that, for the first time, development decisions are being made with a strong scientific input. Personnel from Amigos de Sian Ka an and Grupo Xcaret are now part of the Basin Council of the Yucatan Peninsula (an advisory group that works on water-related areas) and have also been invited to work with the solid residue and water municipal subcommissions in Solidaridad, Quintana Roo. Hydrogeologists are being invited to provide input to be taken into consideration during planning decisions. L ESSONS L EARNED Since the objectives of all three partners were different, a great deal of time was spent identifying common goals and developing a strategy that would meet these goals. To achieve this, academics, NGO workers and members of the business community had to develop a common language and agree on a set of ranked priorities. One of the biggest obstacles faced during the implementation of this case study was convincing local authorities and industry leaders that the aim of the project was not to halt development but rather that project participants wanted to work with them to ensure an ample supply of clean water on a sustainable basis. I MPACT Although the proposed hydrogeological reserve zone around Merida has not yet been accepted by the local authorities, a high permeability zone, the Ring of Cenotes, which hydrogeologically isolates the Merida Block, has now been recognized in the State water management plan for the Yucatan. In addition, many ideas on how to explore and manage groundwater resources in Mexico are emerging from the Yucatan experience. Recently, for example, a Centre for Water Studies was created to address the regional water issues affecting the peninsula. Private industry in the Yucatan, primarily tourism, has also recognized the importance of developing a sustainable groundwater management plan for the Riviera Maya. As a result of the support received from private industry, better relationships are being established between academia and federal, State and municipal government officials. A major factor behind the success of the project has been the fact that three independent groups were working towards the same goal: to preserve and manage in a sustainable manner the groundwater supplies of the Yucatan Peninsula. As a result, the message being delivered by these groups has reached a broad audience of policy-makers.

8 94 V OLUME 11: SAFE D RINKING WATER F UTURE P LANS Lobbying for the creation of the hydrogeological reserve zone for Merida, proposed in 2000, will continue. In addition, proposals for the creation of other hydrogeological reserve zones throughout the peninsula, particularly on the eastern coast, are being developed. In the northeastern part of the peninsula, however, the rate of development is so high that it may already be too late to implement any meaningful sustainable water management programme there. Even so, efforts are under way to raise the issues with regard to conserving water supplies. Xel-Ha, a water park that hosts more than 500,000 visitors a year, has a strong environmental programme aimed at schoolchildren. Currently, park managers are working with UNAM scientists to develop a comprehensive water conservation (in terms of both quantity and quality) management plan. Finally, owing to the presence of many hotels and the tourism infrastructure, many international workshops are held on the Yucatan Peninsula. Plans are being made to hold meetings aimed at sharing more widely the experiences outlined in this case study, particularly with Caribbean countries that share many problems similar to those of the Yucatan. P UBLICATIONS Steinich, B. and Marín, L.E. (1996). Hydrogeological investigations in northwestern Yucatan, Mexico, using resistivity surveys. Ground Water, 34: Escolero, O., Marín, L.E., Steinich, B. and Pacheco, J. (2000). Delimitation of a hydrogeological reserve for a city within a karstic aquifer: the Merida, Yucatan, example. Landscape and Urban Planning, 51: Marín, L.E., Steinich, B., Pacheco, J. and Escolero, O.A. (2001). Hydrogeology of a contaminated sole-source karst aquifer: The case of Merida, Yucatan, Mexico. Geofísica Internacional, 39: Pacheco, J., Cabrera, A. and Marín, L.E. (2001). Nitrate temporal and spatial patterns in twelve water supply wells, Yucatan, Mexico. Environmental Geology, 40: Marín, L.E., Pacheco, J.A. and Méndez, R. (2004). La Hidrogeología de la Península de Yucatán (Hydrogeology of the Yucatan Peninsula). In El Futuro del Agua en México. B. Jiménez and L.E. Marín (eds.), Academia Mexicana de Ciencias, Mexico City, Mexico, p Marín, L.E. (February 2004). Role of science in managing Yucatan s groundwater, in review. National Academy of Sciences/Academia Mexicana de Ciencias, report from Science-based decision making for sustainable ground water management, L.E. Marín and H. Vaux (eds.). (In press).

9 Improving groundwater management: Mexico 95 Prepared by Luis E. Marín Address: Instituto de Geofísica, Universidad Nacional Autónoma de México, Cd. Universitaria, México, D.F., México CP James Coke and Samuel Meacham, Quintana Roo Speleological Survey and the Centro Investigador del Acuifero de Quintana Roo: Work on the underwater mapping of the cave systems. Tel.: (+52) Fax: (+52) Project participants: Oscar Escolero, Instituto de Geología: Work on the water management plan for the Yucatan Peninsula. Patricia Beddows, McMaster University, Hamilton, Canada: Work on the hydrogeological characterization of the aquifer. Mario Rebolledo, Centro de Estudios del Agua, Centro de Investigaciones Científicas de Yucatán: Work on the geophysical characterization of the cave systems. Jorge Luis Basave, Amigos de Sian Ka an: Work on a sustainable management plan for the peninsula. Ana Lilia Cordova, Grupo Xcaret: Work with the government (State and municipal), NGOs and national and local academic institutions.

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