Transboundary Ground-Water Resources along the U.S.-Mexico Border:
Challenges and Opportunities
By:
Lloyd H. Woosley, Jr., P.E.
U. S. Geological Survey Reston, VA, USA
The 2,000-mile international border between the United States and Mexico has experienced significant economic expansion, population growth, and urban development over the past three decades. Since the removal of international trade barriers with the signing of the 1993 North American Free Trade
Agreement, the region’s several small to mid-size cities now are some of the fastest growing population centers in both countries. While this growth has
brought new economic opportunities to the border, the region’s per capita income remains far below the national average in the U.S. According to a bi-national assessment completed in 1999, 12 percent of the border population did not have access to potable water, 30 percent lacked access to wastewater treatment facilities, and 25 percent needed access to solid waste disposal facilities (U.S.
General Accounting Office, 2000).
The surface-water supplies along the international border have been allocated for several decades under international treaties and domestic laws. To meet
expanding water demands, border communities have increasingly relied on the 20 or so shared aquifers underlying the international border (actual number cannot be verified based on available information). In the U.S., the states are responsible for regulating and allocating ground-water resources. The
transboundary implications of ground-water use may not always be a consideration, such as when a state applies the right-of-capture doctrine.
The extensive development of ground water in the border region has depleted stream flow, captured natural discharge, and lowered water levels in many aquifers, resulting in reduced stream flows and decreased quality of aquatic and riparian habitat. The problems associated with limited water quantity and
competing uses of water also have in some areas resulted in impaired and degraded water quality. Little is known about the availability, sustainability, and quality of transboundary aquifers. Information is lacking on how ground water interacts with surface water and on the susceptibility of ground water to
contamination. Water quantity and quality will most likely be the determining and limiting factors that ultimately control future economic development and
population growth on both sides of the U.S.-Mexico border.
In recent years, the need for information on transboundary aquifers has become more widely recognized. The Good Neighbor Environmental Board (GNEB), an independent Presidential advisory board, is the only U.S.-Mexico border
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environmental advisory group in the U.S. that operates by consensus and reflects perspectives from virtually every sector: private; academic; local, state, and Federal government; tribal; and non-governmental organizations (GNEB, 2005, p. 1). In its first annual report, the Board (1995) recommended that:
• Environmental information gaps and accessibility be addressed as a high priority
• Existing data should be identified
• Standards and methods for collection and analysis of data should be coordinated bi-nationally
• Data, analyses, and options should be disseminated widely to
government decision makers, organized interest groups, and affected communities.
In its most recent annual report, the Board (2005) indicates that no legal regimes or institutions exist for managing water quality, supply, or pumping of aquifers that cross the border. If the U.S.-Mexico border region’s water resources are to be managed sustainably, the foundation for all such work needs to be a set of reliable, bi-national integrated databases that are widely accessible (GNEB, 2005, p. 19). The Board further recommends that:
• Formal agreements be developed for border region water-resources data that support the collection, analysis, and sharing of compatible data;
• Bi-national data protocols be developed and applied, specifying field and laboratory methods, quality-assurance and quality-control requirements, minimum data documentation (metadata), and standardized data exchange protocols;
• Special emphasis be placed on the collection and dissemination of ground-water data, including more focus on transboundary aquifers;
• Short-term and long-range plans be developed to fill data gaps in existing surface-water and ground-water inventories in both countries;
• Water data be released for the border region as soon as appropriate after collection and quality assurance; and
• Annual U.S.-Mexico water-quality data exchange be established with the goal of developing an online directory, with links to Federal, state, and local water-quality data sites in both countries.
In recognition of the need for scientific information on transboundary aquifers, the U.S.-Mexico Transboundary Aquifer Assessment Act was introduced into the 109th U.S. Congress (2005). The purpose of this Act is to establish a
transboundary aquifer assessment program to systematically assess priority transboundary aquifers, and provide the scientific foundation necessary for state and local officials to address pressing water resource challenges in the U.S.- Mexico border region. The program will create a geographic information system
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(GIS) database to characterize the spatial and temporal aspects of each priority transboundary aquifer, systematically collect new ground-water data necessary to adequately define aquifer characteristics, and develop ground-water flow models, including modeling of relevant ground-water and surface-water interactions to assist water-management agencies.
The Act calls for the U. S. Geological Survey (USGS) to expand existing
agreements with the border states, water resources research institutes, and other appropriate authorities in the U.S. and Mexico, to conduct joint scientific
investigations, and to archive and share relevant data. Priority transboundary aquifers specified in the Act include the Hueco Bolson and Mesilla aquifers underlying parts of Texas, New Mexico, and Mexico; the Santa Cruz River Valley aquifer underlying Arizona and Sonora, Mexico; and the San Pedro aquifer underlying Arizona and Sonora, Mexico.
The lack of a standardized, bi-national, long-term systematic database to determine ground-water storage change, water use by category, and ground- water quality is perhaps the most important impediment to addressing this complex, water resource challenge in the U.S.-Mexico border region. The USGS in partnership with state, local, and other Federal agencies; academia, and Mexico is committed to collecting the scientific data and developing the knowledge needed for improving the understanding of transboundary ground- water resources.
References
Good Neighbor Environmental Board, 1995, First Annual Report of the Good Neighbor Environmental Board, October 1995, U.S. Environmental Protection Agency, Washington, D.C.
Good Neighbor Environmental Board, 2005, Water Resources Management on the U.S.-Mexico Border, Eighth Report, February 2005, U.S. Environmental Protection Agency, Washington, D.C.
http://www.epa.gov/ocem/gneb/gneb8threport/gneb8threport.pdf
United States Congress, 2005, United States-Mexico Transboundary Aquifer Assessment Act, S. 214 introduced in the Senate on January 31, 2005, H.R.
469, Introduced on February 1, 2005, U.S. Library of Congress, http://thomas.loc.gov/
United States General Accounting Office, 2000, U.S.-Mexico Border: Despite Some Progress, Environmental Infrastructure Challenges Remain, March 2000, GAO/NSIAD-00-26, Washington, D.C.
http://www.gao.gov/new.items/ns00026.pdf
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Presented at:
UNESCO-IHP Hydrogeology and International Law Meeting Paris, France
March 7, 2005
