Transboundary Water Resources and Public Health in the U.S.-Mexico Border Region
Varady, Robert G., Mack, Maura D., Journal of Environmental Health
Background: Environment of the Twin Cities of Nogales, Arizona, and Nogales, Sonora
The U.S.-Mexico border region stretches nearly 3,000 kilometers from the Pacific Ocean to the Gulf of Mexico [ILLUSTRATION FOR FIGURE 1 OMITTED]. Metropolitan Nogales, the site of study, lies on the Arizona-Sonora frontier, within the western quarter of the U.S.-Mexico border. The area encompassing the twin cities of Nogales, Arizona, and Nogales, Sonora, (known in Spanish as Ambos Nogales - literally, "Both Nogaleses") shares a common history, culture, and economy. As importantly, the two cities share a physical environment.
As everywhere, this environment, its natural resources, and its dynamic processes do not respect human-created international boundaries. The interdependent nature of transboundary resources is nowhere better illustrated than in the water resources of Ambos Nogales. The Santa Cruz Basin Aquifer, upon which the two cities depend for their water supplies, is bisected by the border at Nogales. The aquifer is fed by the Santa Cruz River that originates in Arizona, loops down into Sonora and back up toward Tucson. A tributary, the Nogales Wash, flows through both cities and joins the Santa Cruz not far from the International Wastewater Treatment Plant that handles the sewage (liquid and solid waste, as opposed to sewerage, a term used throughout this paper to describe a system for removal of sewage) from both communities. Most of the surface flow of the Santa Cruz originates from effluent discharges and results in a rich, restored downstream ri-parian habitat.
The Sonoran Desert, within which the Ambos Nogales communities lie, is an area of relatively low annual rainfall (400 mm or 16 inches) and seasonally hot temperatures. But as in other dry regions, the climate is characterized more by pronounced variation than by averages. Alternating extremes of drought and flooding are not uncommon, and both of these conditions, the present paper will show, can significantly affect public health.
The metropolitan area's topography features steep hillsides that slope downward from south to north, creating a basin in which surface water, groundwater, and air currents migrate to the United States (2). This landscape combined with shallow soils and sparse vegetation on the hillsides render the area prone to flooding when normally dry washes (streamlets) and canyons quickly fill by runoff. Such urban flooding often is accompanied by broken sewer and water lines. Storm runoff mixes with industrial contaminants and household waste, exacerbating pollution problems and threatening public health on both sides of the border (2,3).
In Ambos Nogales, centuries-long human occupation has generated land use patterns dictated by landscape, climate, and social needs. The activities resulting from rapid population growth, changes in habitation patterns from the valley floor to higher elevations, expanding industry, and rising commerce have engendered numerous problems. Among the most common are antiquated and decaying infrastructure, chronic shortages of water supply, rising air and water pollution, soil contamination, and resource depletion.
The "Ambos Nogales Water Project"
The "Ambos Nogales Water Project," the unofficial title for "U.S.-Mexico Transboundary Water Resources Management: Bilateral Issues, Policies, and Strategies in the Nogales Region," represents an interdisciplinary study of transnational water management policy. The project was a joint, binational effort undertaken from 1989 through 1993 by the Udall Center for Studies in Public Policy at the University of Arizona and El Colegio de la Frontera Norte (COLEF) in Tijuana and Nogales, Mexico. Funding was provided by the Ford Foundation, from both its New York City headquarters and Mexico City office. The project's goals were to: 1. survey and characterize the shared physical water resources of the Nogales area; 2. determine the various ways in which water is used and managed in a semiarid, urban environment; and 3. …