Washington, DC — It's a deadline that is difficult to meet, and only an act of God could help Mexico. 

By October 24 this year, the North American country is required to share approximately 1 billion cubic metres of water with the United States, as stipulated under the 1944 US-Mexico Water Treaty.

However, scientists caution that this is unlikely without a significant weather event occurring in the country's drought-affected region.

"Unless there is a hurricane to fill up international reservoirs, Mexico will be unable to comply with approximately 1000 million cubic metres in the next three months," Rosario Sanchez, a research scientist at Texas A&M University who studies border waters, tells TRT World.

"More permanent drought conditions in the Rio Grande Basin, increase in water demand by both sides, and reduced water availability in the river has contributed to the problem,” says Sanchez. 

As per the 1944 treaty, Mexico must allocate 1.75 million acre-feet of water from the Rio Grande to the US every five years; that's 350,000 acre-feet yearly. The US must, in return, transfer 1.5 million acre-feet of water from the Colorado River to Mexico each year.

But until April this year, Mexico delivered only about 530,730 acre-feet of water to the US from the river that originates in the San Juan Mountains of Colorado and flows to its mouth at the Gulf of Mexico, between Brownsville in Texas state, and Matamoros in Mexico.

In its April meeting with the US, Mexico committed to increasing water deliveries for farmers in Texas through various sources to address the shortfall. 

"Since April 28, Mexico has delivered roughly 200,000 acre-feet of additional Rio Grande water to Texas. This is according to the IBWC's [International Boundary and Water Commission] 5-year cycle water data report that is updated at least once a month and is current through July 2025," Stephen Mumme, a professor emeritus at Colorado State University, tells TRT World.

"There was no fixed quantity to be delivered, at least officially. The official announcement did not mention any specific quantity to be delivered. Unofficially, it appears that Mexico may have assured USIBWC it would aim for at least 300,000 acre-feet of additional water by October 2025.

Despite Mexico's efforts, scientists doubt it will meet the October deadline.

"The estimated shortfall is 1 billion cubic metres, which is roughly equivalent to 811,000 acre-feet," Dr Hugo Luis Rojas, Coordinator of the Geoinformatics Program at Universidad Autonoma de Ciudad Juarez (UACJ) in Mexico, tells TRT World. 

Rojas says even with the normal rainfall, there is no way Mexico will be able to meet the October deadline.

"To close the cycle, a major hydrometeorological event would be needed — such as a hurricane or a tropical depression that brings significant inflows to the Conchos [a large river in the Mexican state of Chihuahua] and the other tributaries," he says.

"Based on current forecasts, the baseline scenario is that Mexico cannot meet the target. This would only change if an extraordinary rainfall event occurs in the coming weeks," Rojas adds. 

Trump wades into crisis

The US and Mexico remain at loggerheads on multiple issues, including tariffs, irregular immigration, drug cartels, fentanyl and weapons trafficking. 

Tensions over water-sharing flared in April when US President Donald Trump waded into the issue, accusing Mexico of stealing water from Texas farmers and threatening additional tariffs and other sanctions. 

To defuse a potential diplomatic crisis, Mexican President Claudia Sheinbaum agreed to temporarily share more water with the US from the countries' shared rivers.

According to the US-Mexico water treaty, all of Mexico's water debts are cancelled, and a new cycle is initiated if all nationally allotted storage is filled. 

Furthermore, it provides that should Mexico fall short in allocating the water in said cycle, it may request forbearance from the US and roll over its debt to a second cycle, with the condition that all first and second cycle debts are paid at the end of said second cycle.

"Against this background, the current situation and the basis of Texas's complaint is this. The current 5-year water delivery cycle that began in October 2020 is now in its 5th year, and Mexico is well behind in meeting its first cycle obligation," Mumme tells TRT World.

Mumme, who has been studying the way the two countries share water, argues, "Texas legitimately worries that Mexico will fail to meet its treaty obligation in October 2025. And it is disgusted with a pattern of treaty compliance that makes it difficult in any given cycle-year to plan for water availability." 

Mumme says farmers in Texas need to get bank loans to crop a year or two in advance, but this requires evidence of a reliable water supply, which is now in doubt given the current situation.

This, he says, makes Texas less likely to grant a rollover this October should Mexico request it, which is likely to happen, highlighting that the US has always granted Mexico's request for a forbearance.

Issue exacerbated by climate crisis

The crisis has been exacerbated by drought in northern Mexico where water reserves are low and farmers have previously protested planned water transfers to the US from specific reservoirs.

Scientists say the climate crisis has added to the already complicated problems. 

Over time, Rojas says, tensions have risen because of two factors: high hydrological variability of the tributaries, through which Mexico delivers the water to the US, and the mismatch between actual availability and agricultural demands on both sides of the border.

"(Agreements) such as Minute 234 (1969) set procedures for making up deficits at the close of a cycle, and recent IBWC technical documents and academic work underscore the need for clearer rules to declare an 'extraordinary drought' and to manage deficits in the context of climate change," says Rojas. 

Rojas elaborates, citing three key factors that escalated the dispute to a critical juncture.

First, the delivery backlogs within the 2020–2025 cycle and the cycle's closure in October 2025, making any adjustments urgent.

Second, tight hydrological conditions in the basin, where "near real-time IBWC reports show low storage levels in La Amistad and Falcon reservoirs and modest flows in the six tributaries, limiting the operational margin for rapid transfers."

Lastly, and most importantly, drought in northern Mexico, with "visible impacts in Chihuahua (Rio Conchos basin) and variability in agricultural reservoir levels reported by CONAGUA (Mexican national water agency) in 2025; this mix makes it difficult to meet deliveries without affecting local irrigation."

Mumme also highlights the criticality of the drought in this situation, saying that the entire Mexican northern border area and the American southwest have been in the throes of a sustained drought since the mid-1990s, which most climatologists attribute in part to the climate crisis.

"Within the Rio Grande Basin, particularly that part served by the Rio Conchos drainage and other Mexican tributaries to the Rio Grande, annual average precipitation is down. Mexico is right about that," he says.

Mumme contends CONAGUA acknowledged increased water usage due to Mexican irrigation, alongside rumours of unstudied, illicit groundwater taps potentially impacting the Rio Grande.

"There is some righteousness to be had on both sides of the dispute. Mexico, like the US and Texas, is politically obligated to attend to the needs of its own citizens and is trying to do that while meeting its treaty obligations," he says.

It is worth noting that Texas has resisted including references to the climate crisis in recent IBWC agreements on managing the shortage on the Rio Grande river.

This is in contrast to binational agreements on shortage sharing on the Colorado River, where reference to the climate crisis as contributing to basin-wide shortage was put in Minute 317 as early as 2010.

"I can only speculate, but Texas's reluctance to mention climate change in official agreements addressing Mexico's water debt seems related to a concern that such language would strengthen Mexico's claim to be suffering from 'extraordinary drought', hence weakening Texas's claim that Mexico is hoarding water," Mumme notes.

Reviewing old treaty

Despite the rocky situation, Mumme says there were a few agreements that helped make limited but valuable progress to solve the situation.

An IBWC Minute (agreement) 325 in 2020, established binational hydrology and policy workgroups to analyse Mexico's water usage and recommend improvements in Mexican water management that could strengthen its treaty compliance.

"Mexico accepted the basin-wide application of the US's preferred real-time diagnostic software called RiverWare to monitor flows in the watershed. That is a real concession by Mexico," he says.

"Recently, Minute 331 in November 2024 introduced a few new options for Mexican treaty compliance and created two additional workgroups, one on project development and another addressing environmental concerns. This doesn't help South Texas farmers in the short run, but could be of real help over the next decade."

Sanchez, however, says that both countries should recognise that the treaty has its limits, and a new model may be required.

The row "has to be solved on common grounds and recognising that the treaty has limits, and so the basin," she adds.

"The current model does not function anymore, and both countries need to negotiate new agreements to account for current conditions and future scenarios," Sanchez argues.

This dispute, she warns, can "affect everything and get contaminated with other issues (tariffs)  that honestly do not help anything in terms of water issues in the US-Mexico border."

Rojas suggests adapting the treaty with new agreements. This includes climate thresholds, forecasts, irrigation, and strengthened local cooperation for transparency.

"This approach recognises that climate change is not an isolated event, but a new normal. Adapting the treaty to this reality would maintain compliance with international commitments while also protecting the region’s water and food security," Rojas adds.