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1 [1] (August 4, 2025)

handle is hein.crs/iytdd0001 and id is 1 raw text is: Congressional Research Service Inforrning the legislative debate since 1914 Updated August 4, 2025 1944 U.S.-Mexico Water Treaty: Issues in the 119th Congress A water treaty from 1944-the Treaty on Utilization of Waters of the Colorado and Tijuana Rivers and of the Rio Grande (1944 Water Treaty)-between the United States and Mexico and other binational agreements guide how the two governments share flows of the Rio Grande and Colorado Rivers. The 1944 Water Treaty states that the countries agree to give preferential attention to solving all border sanitation problems (e.g., flows of raw sewage and industrial wastewater in the Tijuana River Valley [TRV]). The binational International Boundary and Water Commission (IBWC), which was established in 1944 pursuant to the treaty and administers agreements on river flows and sanitation issues, is the principal venue for addressing related disputes between the United States and Mexico. The IBWC develops rules and proposed decisions, called minutes, on treaty execution and interpretation. During the 119th Congress, U.S.-Mexico water issues have been receiving attention, including Mexico's deliveries in the Rio Grande basin, U.S. approval of diversions from the Colorado River to Mexico, and sanitation concerns related to the TRV. Congressional considerations include how Congress and the executive branch are shaping responses to these matters and the effect on U.S.-Mexico cooperation. Rio Grande The 1944 Water Treaty addresses the Rio Grande basin below Fort Quitman, TX. Among other things, it establishes that the United States has a right to flows from tributaries that feed the Rio Grande in the United States and one-third of specified Mexican tributaries flows, which must average at least 0.35 million acre-feet (MAF) per year, measured in five-year cycles (1.75 MAF total). On multiple occasions since 1994, Mexico has not met its Rio Grande delivery obligations within a cycle. As of late July 2025, which is a few months before the current cycle ends (i.e., the five-year cycle started October 25, 2020, and will end five years later), Mexico's deliveries were estimated at roughly 0.73 MAF for the cycle, according to IBWC. If Mexico fails to meet its minimum Rio Grande flow obligations for a cycle because of extraordinary drought-a term not defined in the 1944 Water Treaty or in any minute-it must replace the deficiency during the next five-year cycle. Concerns about Mexico's repeated occasions of not meeting five-year cycle delivery requirements, and the consequences for the Texas economy, have led some U.S. stakeholders to support the establishment, monitoring, and application of mechanisms to achieve a more reliable and predictable water-delivery regime. Article 24(d) of the 1944 Water Treaty provides mechanisms for dispute resolution if Mexico fails to meet its minimum flow obligations and the countries dispute that an extraordinary drought existed. In early April 2025 on social media, President Trump raised the prospects of sanctions and tariffs when discussing Mexico's water deliveries relative to the amounts specified in the treaty. While Mexico's internal water management influences deliveries, other factors that may contribute to delivery shortfalls under recent cycles identified by stakeholders include drought conditions in portions of Mexico's Rio Grande basin and weather and climate patterns. In late April 2025, the U.S. Department of State announced that Mexico had committed to reducing its shortfall in deliveries and to working with the United States to develop a plan to make up the remaining shortfall and make more dependable deliveries in the next cycle. IBWC data indicate an uptick in deliveries in calendar year (CY) 2025, compared to CYs 2023 and 2024. Historically, Congress has been involved in Rio Grande water-sharing issues through oversight and, at times, direction for enhanced State Department reporting on deliveries and efforts to improve compliance. H.R. 4779 would withhold certain funds that the United States provides to Mexico for various purposes until the Secretary of State certifies that Mexico is implementing certain remedies to address the delivery shortfalls. Considerations for the 119th Congress include what executive branch mechanisms are being employed to influence Mexico's deliveries under the current and next cycles and whether additional minutes-beyond Minute 331, Measures to Improve the Reliability and Predictability of Rio Grande Water Deliveries to Benefit the United States and Mexico, approved in November 2024-are warranted. Colorado River U.S. delivery of Colorado River basin waters to Mexico is part of a broader allocation of basin waters pursuant to the Colorado River Compact (Compact), a seven-state agreement signed in 1923 that apportioned 7.5 MAF annually to both the Upper and Lower Colorado River basins in the United States and delineates how additional waters are to be sent to Mexico pursuant to a subsequent treaty. In the 1944 Water Treaty, the United States agreed to deliver to Mexico 1.5 MAF of Colorado River water per year, plus an additional 0.2 MAF when a surplus is declared. During drought, the United States may reduce deliveries to Mexico in similar proportion to reductions of U.S. consumptive uses. The 1.5 MAF obligation is generally split equally between Upper and Lower Basins. The United States typically has met its Colorado River delivery requirements to Mexico pursuant to the 1944 Treaty. Hydrology on the Colorado River has deteriorated significantly since 2000. During this time, the two countries have negotiated multiple minutes (e.g., Minute 319 in 2012, Minute 323 in 2017) that, among other things, reduced deliveries to Mexico under specified conditions and