1944 Water Treaty Threatened by Climate Stress: Study

A University of Michigan study finds the 1944 US-Mexico Water Treaty increasingly misaligned with current climate realities, as rigid delivery rules and persistent drought strain compliance and fuel recurring bilateral tensions.

The 1944 Water Treaty between Mexico and the United States is facing renewed scrutiny as drought, rising demand, and political pressure expose the limits of a framework designed for a more stable climate.

A University of Michigan study by researchers Vianey Rueda and Andrew Gronewold argues that the treaty’s Rio Grande provisions have not adapted to today’s hydrological conditions. While the Colorado River side of the treaty has been adjusted through later negotiations, the Rio Grande allocation system has remained largely unchanged, despite parallel overuse, drought, and recurring compliance disputes.  

The study, published in the Journal of Water Resources Planning and Management, evaluates how difficult it is for Mexico to comply with the treaty under different streamflow scenarios. Researchers conducted a historical resimulation of treaty deliveries to identify the conditions required for Mexico to meet its obligations. Their conclusion is that prolonged periods of above-average streamflow are needed for Mexico to comply without placing disproportionate pressure on Mexican communities that also depend on the same water sources.  

The study does not simply argue that Mexico is failing to deliver water. It suggests that the treaty’s design is increasingly misaligned with the reality of drought, climate variability, and local water demand. The researchers also tested an alternative delivery strategy and found that more flexible delivery mechanisms could improve treaty compliance while distributing the impact of reduced flows more evenly between both countries.  

Under the 1944 Water Treaty, Mexico is required to deliver 1.75 million acre-feet (2,158.6 million m³) of water over five-year cycles, averaging 350,000 acre-feet (431.7 million m³) annually, while the United States must deliver Colorado River water to Mexico. The problem, according to the study, is that the Rio Grande has not undergone the same adaptive changes seen in Colorado River management.  

The study aims to help explain why the treaty has become a recurring source of diplomatic tension. Throughout 2025, US officials increased pressure on Mexico over delayed water deliveries, including threats of sanctions, tariff warnings, and criticism from Texas agricultural interests, MBN reports. Mexico, meanwhile, argued that drought and limited water availability constrained its ability to meet delivery targets.

The dispute escalated in early 2025 when US Senator Ted Cruz pushed for sanctions over Mexico’s water shortfall, followed by the United States denying Mexico’s request for additional Colorado River water. Later, US President Donald Trump threatened tariffs over Mexico’s treaty deficit. By April 2025, both governments reached an agreement to address the pending deliveries before the five-year cycle ended on Oct. 24, 2025.

However, tensions resurfaced by the end of 2025, when the treaty again came under scrutiny amid historic drought. In December, Mexico and the United States reached another agreement on water deliveries, signaling that both governments were trying to contain the dispute without reopening the treaty itself.

In February 2026, Mexico agreed to deliver at least 432 million m³ annually during the current cycle, a shift toward more predictable yearly deliveries rather than relying only on the five-year average.

The University of Michigan study argues that the issue is not only whether Mexico complies, but whether the treaty’s structure remains viable under current climate conditions. Its findings suggest that rigid delivery rules can intensify pressure on local communities and make compliance politically and technically harder during prolonged drought.