Gulf of Mexico Origin, Waters, and Biota: Volume 4, Ecosystem-Based Management

8 Mexico- United States Shared Environmental Problems in the Rio Grande/Río Bravo Basin Ecosystem

153 ≋ North America (Fig. 8.1). The river drains an area of about 479,720 km2 from the southern Rocky Mountains, through the vast Chihuahua Desert up to the subtropical lower valley of the river that flows into the Gulf of Mexico (Jiménez 2002). The river begins 3660 m above sea level near the Continental Divide in the Rio Grande National Forest of the San Juan Mountains in southern Colorado as a clear, snow-fed, mountain stream. From there, the river flows through the middle of New Mexico and arrives at the boundary between the United States and Mexico near El Paso, Texas, and Juárez, Chihuahua. The 1848 Treaty of Guadalupe Hidalgo established the river from that point to the Gulf of Mexico, a distance of approximately 2000 km, as the international boundary between Mexico and the United States. The total length of the river exceeds 3050 km and contains a diverse array of plants, animals, and more than 11.8 million people live in the international border region. This includes over 6.3 million people living in the US territory and more than 5.5 million living in Mexican territory. By 2020 the human population in the region is projected to reach 19.4 million people including an estimated at 7.6 million in Mexico (SEMARNAT 2003). In the lower valley region of the river and its estuary, the number of human inhabitants in Texas is projected to increase 217% by 2060 (TWDB 2007). Moreover, the overall human population of the basin has doubled every 20 years since World War II and is expected to more than double within the next 30 years (Hooper et al. 1997). This extraordinary population growth will fuel inThe Rio Grande/Río Bravo is a troubled source of life for the environment and the people that its ecosystems support . The United States and Mexico share many common problems along this legendary river, and the extent to which they work together will determine not only the future of the river but the future of the inhabitants of the river basin as well. The environmental stressors are a list too familiar: dewatering of the river through increasing impoundment and diversion activities; water pollution from municipalities and industry, agricultural inputs of salts, nutrients, raw sewage, toxic pesticides, herbicides, and other chemicals and heavy metals; introduced exotic plants and animals; habitat loss through deforestation and other land-use changes; climate change that could be making the basin more inhospitable and difficult to manage ; and a burgeoning human population that is creating its own tidal wave of crisis. Added to the management issues are important socioeconomic , cultural, technical, and agricultural differences between both nations sharing this international border. The aim of this chapter is to present a new starting point for focusing environmental policies on mitigating these negative effects throughout the socioeconomic and ecological systems dominating this region. Environmental Setting The Rio Grande, known as the Río Bravo on the south side of the border, is one of the largest river basins in 8 Mexico-United States Shared Environmental Problems in the Rio Grande/Río Bravo Basin Ecosystem Sergio Jiménez-Hernández and Gary L. Powell 154 ~ Jiménez-Hernández and Powell barriers to reallocation (Mathews et al. 2001). Other barriers are inherent in the appropriation doctrine, and some barriers exist due to poor data or inadequate science. These barriers could be more easily overcome and the processes less political if the effects of these changes were more clearly understood. After more than 300 years of settlement activity, the Rio Grande/Río Bravo is still considered a dynamic frontier of hope but also of great despair due to water contamination , poverty, and international legal issues that comcreased urban demands for water and will simultaneously cause reductions in irrigation, which together account for more than 80% of total water use because agricultural water supplies will be converted to domestic and urban (municipal and industrial) uses to cover deficits in this sector from actual and future users. Reallocating water is a politically sensitive issue in both the United States and Mexico. The change in water uses from agricultural to urban or environmental is occurring, but the process tends to polarize competition among water users, creating Figure 8.1. Rio Grande/Río Bravo hydrological basin (IBWC 2001). Rio Grande/Río Bravo Basin Ecosystem ~ 155 tropical and temperate latitudes allows it...