The United States and Mexico are fighting for their dwindling shared water supplies after years of unprecedented heat and insufficient rainfall.
Sustained drought in the lower-middle Rio Grande since the mid-1990s means that less Mexican water flows to the United States. The Colorado River basin, which supplies seven states in the United States and two in Mexico, is also at record low levels.
A 1944 treaty between the United States and Mexico governs water relations between the two neighbors. The International Boundary and Water Commission he established to manage the 450,000-square-mile basins of Colorado and Rio Grande has done it skillfully, according to our research.
This management kept the water relations between the United States and Mexico, for the most part, free of conflict. But it masked some well-known underlying tensions: a population boom on both sides of the US-Mexico border, climate change and aging waterworks.
1944 al 2021
The mostly semi-arid border region between the United States and Mexico receives less than 18 inches of annual rainfall, and large areas are less than 12 inches. That’s less than half the average annual rainfall in the United States, which is mostly temperate.
The 1940s, however, were a time of unusual abundance of water in the treaty rivers. When US and Mexican engineers wrote the 1944 water treaty, they did not foresee today’s protracted mega-drought.
They also did not anticipate the rapid growth of the region. Since 1940, the population of the 10 largest city pairs that straddle both sides of the US-Mexico border has increased nearly twenty-fold, from 560,000 to about 10 million today.
This growth is driven by a booming water-dependent manufacturing industry in Mexico that exports products to US markets. Irrigated agriculture, ranching and mining compete with growing cities and expanding industry for water scarcity.
Today simply not enough to meet demand in border areas governed by the 1944 treaty.
Three times since 1992, Mexico has not fulfilled its five-year commitment to send 1.75 million acre-feet of water across the border into the United States. Each acre-foot can supply an American family of four for a year.
In the fall of 2020, the crisis erupted in the Rio Grande Valley after years of mounting tensions and sustained droughts that endanger crops and livestock in both the United States and Mexico.
In September 2020, Texas Governor Greg Abbott declared that “Mexico owes Texas a year’s worth of Rio Grande water.” The following month, workers in Mexico discharged water from a dammed portion of Mexico’s Rio Conchos destined to cross the border to partially pay Mexico’s 345,600 acre-foot water debt to the United States.
Frustrated farmers and protesters in the Mexican state of Chihuahua clashed with Mexican soldiers sent to protect workers. A 35-year-old farmer’s wife and mother of three have died.
Mexico also agreed to transfer the water stored at the Amistad Dam to the United States, fulfilling its obligation just three days before the October 25, 2020 deadline. That decision satisfied its water debt to the United States under the 1944 treaty. , but endangered the supply of more than a million Mexicans living downstream of the Amistad dam in the Mexican states of Coahuila and Tamaulipas.
The United States and Mexico pledged to review the treaty’s Rio Grande water rules in 2023.
The dilemma of the drought on the Colorado River is just as dire. The water level in Lake Mead, an important reservoir for communities in the lower Colorado River, has fallen almost 70 percent in 20 years, threatening the water supplies of Arizona, California and Nevada.
In 2017, the United States and Mexico signed a temporary “shortage sharing solution”. That agreement, forged under the authority of the 1944 treaty, allowed Mexico to store some of its treaty water in US reservoirs upstream.
Save a tense treaty
Water shortages along the U.S.-Mexico border also threatens the natural environment. As water is channeled to farms and cities, rivers are deprived of the flow necessary to maintain habitats, fish populations, and the general health of rivers.
The 1944 water treaty was silent on conservation. Despite all its strengths, it simply allocates water from the Rio Grande and Colorado rivers. It does not consider the environmental side of water use.
But the treaty is reasonably elastic, so its members can update it as conditions change. In recent years, conservation organizations and scientists have promoted the environmental and human benefits of restoration. The new Colorado River agreements now recognize ecological restoration as part of treaty-based water management.
Environmental projects are underway in the lower Colorado River to help restore the river delta, emphasizing native vegetation such as willows and poplars. These trees provide habitat for birds at risk such as the yellow-billed cuckoo and the Yuma clapper, and for numerous species that migrate along this desolate stretch of the Pacific Flyway.
Currently, no such environmental improvements are planned for the Rio Grande.
But now other lessons learned in the Colorado are being applied to the Rio Grande. Recently, Mexico and the United States created a permanent binational advisory body for the Rio Grande similar to the one established in 2010 to oversee the health and ecology of the Colorado.
Another recent agreement allows each country to monitor the other’s Rio Grande water use using common diagnostics such as Riverware, a dynamic modeling tool for monitoring water storage and flows. Mexico also agreed to try to use water more efficiently, allowing more to flow to the United States..
Newly created joint teams of experts will study treaty compliance and recommend additional changes needed to manage the climate-threatened waters along the US-Mexico border in a sustainable and cooperative manner.
Incremental treaty modifications like these could palpably reduce last year’s tensions and revitalize a historic treaty between the United States and Mexico that is collapsing under enormous pressure from climate change.
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* By Robert Gabriel Varady, Professor of Environmental Policy Research at the University of Arizona; Andrea K. Gerlak, professor at the University of Arizona School of Geography, Development, and Environment; and Stephen Paul Mumme, Professor of Political Science at Colorado State University.
*The Conversation is an independent, nonprofit source for news, analysis, and commentary from academic experts.