Protecting border groundwater in Ambos Nogales: Application of the Segerson model and the Bellagio Draft Treaty to the Arizona-Sonora border

Abstract

The purpose of this dissertation is to examine potential solutions to the problem of groundwater contamination between Arizona and Sonora, Mexico. The focus of the study is the binational Santa Cruz River, and other groundwater resources, shared by the two countries. The Santa Cruz River runs through the shared farming and cattle-raising areas to the south and east of Nogales, Sonora and Nogales, Arizona (Ambos Nogales). In addressing the potential problem of contamination in this border area, two approaches are applied to address this potential problem. First, an economic model, the Kathleen Segerson model, which was developed to assess the liability of farmers and agricultural chemical manufacturers in the United States, was expanded to include Mexico and to examine cross-border agricultural contamination. Secondly, a binational groundwater management model, the Bellagio Draft Treaty, was applied to the region of Ambos Nogales to see how it might work in addressing both cross-border agricultural contamination on the Santa Cruz River, as well as industrial and bacterial contamination in the Nogales Wash. Segerson showed that an economically efficient solution could be achieved by holding agricultural chemical manufacturers liable for groundwater contamination. However, the legal difficulties associated with establishing manufacturer liability are numerous and substantial. In addition, holding farmers to best management practices in Mexico is doubtful based on Mexico's ineffective environmental regulatory system. Because of these difficulties, the conditions established by Segerson for the model to work cannot be met. A more effective solution lies in the Bellagio Draft Treaty. The Bellagio Draft Treaty was determined to be a potentially effective way to solve a spectrum of border water issues for the Ambos Nogales area. Some of the problems that could be addressed under the Draft Treaty include: water contamination, equitable division of shared water, health emergencies, and drought planning and response. While this dissertation determines that the Bellagio Draft Treaty could be applicable to the water related problems of Ambos Nogales, the author states that much work will be needed to actually expand the powers of a potential management agency, such as the International Boundary and Water Commission (IBWC).