In April, there was a post.
“We will keep escalating consequences, including TARIFFS and, maybe even SANCTIONS, until Mexico honors the Treaty, and GIVES TEXAS THE WATER THEY ARE OWED!” President Donald Trump wrote on his Truth Social account.
The president’s signature declarative, all-caps style had collided with the highly technical realm of water negotiations between the United States and Mexico. It’s a world governed by an 81-year-old treaty that binds the two neighbors’ taps at a time when water is increasingly scarce on the border.
After years of drought, Mexico is failing to come up with the water it owes the United States under that treaty.
“Everybody wants the same amount of water that they used to,” said Rosario Sanchez, a research scientist at Texas A&M University who studies border waters. “Right now, we don’t have enough water for all the uses or all the users.”
As that reality leaves some Texas farmers dry, Trump has found a perhaps obvious avenue to pursue his goal to ensure the United States is getting a fair shake on the world stage. But some experts fear bringing tariff threats and “America First” rhetoric into the world of water negotiations will backfire, and that the careful work of administering the 1944 water treaty could get damaged in the process.
“The 1944 water treaty is easily one of the most important treaties that we’ve ever signed with Mexico,” said Stephen Mumme, a professor emeritus at Colorado State University who has studied the way the two governments share water for decades.
The treaty is a complex document, but it requires the United States to deliver water from the Colorado River to Mexico, and Mexico to deliver water from the Rio Grande to the United States.
Following a years-long drought, Mexico has only delivered less than half of the water it owes the United States in a five-year cycle that ends this October. The United States, on the other hand, is set to deliver the water it owes to Mexico by then.
After Trump threatened tariffs in April, Mexico’s president did announce an additional water shipment to Texas from Mexico’s reservoirs on the Rio Grande. But experts say there just isn’t enough water available for Mexico to get back on track by October.
The two countries owe each other 1.75 million acre-feet of water every five years. That’s enough water to cover 1.75 million acres of land with a foot of water. The amount that Mexico still owes the United States by October would be enough water to sustain Phoenix households for about five years.
Experts like Mumme say Mexico would need an act of God — a giant hurricane, for example — to come up with the water it needs to fulfill its obligation to the United States by October. Many of northern Mexico’s reservoirs are low or empty, and in some places, a lack of rain means rivers run dry.
“The God-honest truth is there’s not that much that can be done,” Mumme said. “You can’t make Mother Nature do anything other than Mother Nature intends to do.”
Even though it’s behind on its deliveries of water, Mexico has helped the United States in other ways, Mumme said. For instance, it stores some of its water in Lake Mead, thus helping keep water levels there higher.
But there are farmers in Texas who rely on Mexico’s water deliveries. Last year, Texas’ last sugar mill closed, citing Mexico’s failure to fulfill regular water deliveries
“The focus in Texas has been maximalist. ‘We absolutely insist on getting our treaty-defined water entitlement from Mexico,’” Mumme said. “They’re within their right to claim that.”
That attitude has been echoed by the Trump administration, which Mumme says has an incentive to appeal to elected Republican officials in Texas.
Some experts, like Mumme, think that careful diplomacy and communication between the two countries could result in a more regular schedule for water deliveries from Mexico to Texas, which would alleviate uncertainty for farmers there.
“The use of bullying tactics in U.S.-Mexican water diplomacy, which has been an area defined by a high level of cooperation over many, many years, just doesn’t work very well,” Mumme said. “Unfortunately, that seems to be the signature feature of Trump administration diplomacy.”
Water treaty negotiations happen through the International Boundary and Water Commission, the binational agency that applies the treaty. Those negotiations occur “every single day,” said Francisco Lara-Valencia, a professor who studies cross-border urban development at Arizona State University.
The treaty doesn’t just deal with water sharing between the Colorado River and the Rio Grande. It also governs cross-border water sanitation issues and water sharing between smaller cross-border rivers. Sanitation has been an important topic for the IBWC over the years, as it tries to manage sewage overflow from Mexico into the United States in Tijuana and San Diego, as well as in Ambos Nogales.
“The IBWC is constantly trying to find solutions to these problems,” Lara-Valencia said.
Gabriel Eckstein, a law professor at Texas A&M University, said public negotiations between Mexico and U.S. presidential administrations put IBWC dealmakers in a difficult spot.
“I do think it makes it a lot more difficult for them to operate,” Eckstein said.
Some observers think the federal government has a duty to stay involved in Colorado River allocation negotiations, as well as water diplomacy with Mexico. It’s the only entity that can bring all the relevant parties to the negotiating table, said Andrew Gould, a lawyer and former Arizona Supreme Court justice.
“That’s the only entity that can do it,” Gould said. “The hope would be that maybe something could be brokered.”
Arturo Sarukhán, a former Mexican ambassador to the United States, thinks Trump’s strategy to link issues like water and migration to tariffs could hurt other parts of the U.S.-Mexico relationship.
“The relationship is so, so, so broad and so complex, that once you start mixing and matching and linking one issue to nonrelated thematic issues, the danger is that all of the agenda and all of the relationship simply freezes,” Sarukhán said.
For now, Mexico is able to push its debt of water into another five-year cycle come October. The treaty allows that in cases of extraordinary drought.
Sarukhán said a drier future will require the two countries to work together to figure out how to divide the water that flows between them.
“We’ve kicked the can down the road, but we’re not structurally addressing the challenges that we’re going to be facing regarding what is very likely gonna be a drier and drier northern Mexico and Southwest U.S.,” Sarukhán said.
