When determining borders, a river is often the clearest delineation between sovereign nations. But that clarity abruptly ends when countries must decide how to use the water that the river provides. Even managing rivers that do not determine borders, but rather travel through multiple countries, is precarious at best. The Rio Grande, which partly establishes the U.S.-Mexico border, is no exception. It has been and will continue to be vital to economic growth in the region, especially in Mexico, where the river and its tributaries are crucial to supporting new opportunities for manufacturing and energy.
But growing demands and environmental pressures will increase tension over water resources in the coming decades. Unlike the waters of the Colorado River, which originate entirely in the United States, the watershed of the Rio Grande is more evenly split between the United States and Mexico. Although Mexico depends on the water resources far more than the United States does, both nations are vulnerable to increasing water stress, making it difficult for them to meet anticipated water treaty obligations.
Exceptional Management
The Rio Grande is more than just the main river that runs along the Mexican border of Texas, emptying into the Gulf of Mexico. Its upper reaches stretch as far north as Colorado, though the majority of the basin area in the United States lies in New Mexico. Because of a combination of factors — such as high evaporation rates in the arid region, diversions for agricultural production in New Mexico and invasive plant species — a portion of the Rio Grande effectively dries up before being replenished at its confluence with the Rio Conchos. The Rio Conchos runs entirely through Mexico’s territory, beginning in the mountains of Chihuahua and Durango and moving through the Chihuahuan Desert, and it accounts for roughly 14 percent of the Rio Grande’s total watershed. On the U.S. side, one of the Rio Grande’s primary tributaries, the Pecos River, runs through New Mexico before joining up again with the larger river farther south.
Yet the cooperation between the United States and Mexico over the river systems of the Colorado and the Rio Grande (or Rio Bravo, as it is known in Mexico) is in some ways exceptional by international standards. Treaties signed in the first half of the 20th century clearly dictate the volumes of flow guaranteed to each country, and those agreements have successfully forestalled many past disputes. Specifically, the river’s use is governed in two separate sections, with Fort Quitman, Texas, acting as the dividing point for legislation and management.
It was not until the late 19th century that legal disputes over the use of the Rio Grande began. At the time, U.S. courts determined that the country had no legal obligation to deliver any water downstream. A 1906 case, however, determined that roughly 74 million cubic meters per year would be delivered to Mexico from the northwestern parts of the river but stipulated that the amount could be reduced in drought years. There were reductions in roughly a third of the years between 1939 and 2015. In fact, Mexico has not received the full allotment since 2012, and as little as 6 percent of the full amount was delivered in 2013.
Along the southeastern portion of the Rio Grande, downriver from Fort Quitman, the allotments are governed by the 1944 water treaty, which requires Mexico to receive two-thirds of the water from its tributaries and to deliver the remaining third to the United States. These deliveries are somewhat flexible because the amount (just over 430 million cubic meters per year) is tracked in five-year blocks, and one year’s deficit can be accounted for in the next year if necessary. Even if a deficit spans the entire five-year block, as was the case for much of the 1990s as well as from 2010 to 2015, it can still be compensated for in the following five-year span. Mexico even made up its accumulated deficit of 325 million cubic meters within the first few months of 2016. Still, the uncertainty over consistent volumes of delivery sometimes leads to calls for political action, especially for consumers in Texas.
In addition to the two countries’ shared surface water, Mexico and the United States share about 20 underground aquifers. Though these resources support the populations and economies of the border region, unlike surface water, no international treaty governs their use. Much like surface water, however, there is significant overexploitation and a decline in water quality. Consistent overuse ultimately threatens the viability of the aquifer systems.
Demand Factors
When these agreements were signed in the early 20th century, less was known about the hydrology of the region, and the Rio Grande’s limited water resources were likely over-allocated based on above-average yearly flows. Furthermore, demand is growing, not shrinking. Agriculture is the primary consumer of the basin’s water, but expanding populations that could reach nearly 20 million people by 2020, the rapid rise of manufacturing capacities in Mexico (following North American Free Trade Agreement) and energy production on both sides all play a role in increasing water stress in the region.
Mexican manufacturing capacity, especially in the automotive sector, may be slowing after having swelled between 2008 and 2014. But buoyed by the increasing number of nearby U.S. consumers, high-end manufacturing will soon determine Mexican economic growth, and water consumption by the sector will only rise.
Manufacturing growth has also propelled the rapid expansion of Mexico’s electrical grid and, in turn, the demand for energy: Mexico continues to rehabilitate its energy sector to revive production levels. And while the full benefits of Mexico City’s recent energy reforms have yet to be seen, the energy sector will likely increase its water consumption (including for hydraulic fracturing) at sites located in the Rio Grande Basin. Moreover, Mexico will not be the only country drawing from the Rio Grande or aquifers to support energy production. Agriculture is the primary consumer of water in Texas, but the Eagle Ford shale formation crosses the Mexican border, and production on the U.S. side has already increased water use in several river basins over the past decade, a pattern that will likely continue.
All of these factors contribute to current estimates that upper portions of the river will decrease by as much as a third by the end of this century, and lower portions will accumulate a deficit of more than 830 million cubic meters per year. The gap between supply and demand will grow, as will tension along the border. The treaties, signed decades ago, have been sufficient and their terms largely met until now. But overuse of water resources and environmental stress continue to rise, and basin conditions are poised to prevent amiable management of the water system in the long term. Efforts from both the private sector and governments will instead likely focus on implementing technological adaptations, including waterless hydraulic fracturing and water recycling, to mitigate water stress. Nevertheless, dwindling water supplies could hamper manufacturing growth and energy production in the basin, especially for Mexico. Moreover, Mexico’s likely failure to meet delivery quotas will only ramp up tensions with the United States in the coming decades.
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