The upcoming change in the U.S. presidential administration, with its threat of tariffs and mass deportation of immigrant communities, has put more attention on the country’s southern border. Despite these and other tensions concerning the U.S.-Mexico border, Mexico and the United States continue to work together to negotiate new approaches and compromises to manage shared water resources sustainably, even as climate change and drought have reduced those supplies. The International Border and Water Commission (IBWC), established in 1889, is tasked with applying the boundary and water treaties between Mexico and the United States and resolving questions or differences that arise.
On November 7, 2024, Maria Elena Giner, Commissioner of the U.S. Section of the IBWC, and Adriana Resendez, Commissioner of the Mexico Section, cemented another link in their countries’ long relationship over water. The two leaders signed a new agreement (or “minute”) under the 1944 Treaty that governs the Rio Grande intended to ensure more regular water deliveries from Mexico to the United States in the Rio Grande/Río Bravo basin. Recent decades have seen increasing cyclical uncertainty and tension about how and when Mexico would deliver water. In the end, Mexico has never failed to meet its obligation, but many farmers in Texas are bearing the cost of the uncertainty and unpredictability.
The 1944 Treaty obligates Mexico to deliver to the United States a minimum annual average of 350,000 acre-feet of water from specified tributary systems in the Rio Grande basin in five-year cycles, except in the event of extraordinary drought or serious accident to its water infrastructure. Mexico is obligated to deliver 1.75 million acre-feet by the end of the current cycle on October 24, 2025; it has to date delivered a total of 425,405 acre-feet this cycle (a bit less than 25% of what is obligated). Minute 331, titled “Measures to Improve the Reliability and Predictability of Rio Grande Water Deliveries to Benefit the United States and Mexico,” provides Mexico with tools and flexibility to deliver water earlier than what was set forth in the five-year cycle per the 1944 Treaty.
Minute 331 is the first minute to substantially change or expand water delivery mechanisms since Minute 234 was signed in 1969. The new agreement seeks to create change around two elements: how Mexico manages its reservoirs, and how the United States takes water. Water in Mexico is managed at the national level, with the National Water Commission (CONAGUA) granting allocations (concessions) across the country, primarily by use. The new agreement acknowledges the importance to the United States of incorporating Texas water deliveries in Mexico’s annual allocation plans. It also sets out options for Mexico to deliver water with more flexibility and, ideally, more reliability. Paragraph 6 provides that where storage in a Mexican reservoir on a tributary named in the treaty exceeds normal conservation capacity (NAMO), Mexico “shall release excess volumes downstream with the goal that they reach the Rio Grande mainstream.” Previously, Mexico has delivered only volumes of water that it was unable to store; now, the threshold for release is lower.
The Paragraph 6 provision also requires Mexico—when its domestic and municipal supply is guaranteed—to “evaluate the possibility of allocating volumes for the fulfillment of its obligations” when: (1) there is a deficiency from a previous cycle; or (2) to reduce or avoid a potential deficiency when its deliveries are below the minimum annual average established in the treaty for the current cycle. Minute 331 conditions the delivery of water via the specified means on the prior agreement of the parties in an exchange of letters between the U.S. and Mexican sections of the IBWC, and notes that the United States must have the storage capacity to conserve the water. Waters from rivers that the treaty allocates completely to Mexico (the San Juan and Alamo) are listed as being available to Mexico to reduce or avoid a potential deficiency when Mexico does not need the water and the United States is able to put it to beneficial use.
Additionally, Minute 331 provides for a Projects Work Group to develop water conservation efforts and make recommendations to the IBWC for the benefit of both countries, similar to efforts previously carried out in the Colorado River basin. Projects that may be considered include the construction of control infrastructure, water reuse, irrigation conservation and modernization, and the study of desalination projects. The new agreement also establishes a binational Environment Work Group to address environmental issues in the international reach of the Rio Grande and formalizes the Lower Rio Grande Water Quality Initiative to address water quality concerns, especially salinity. The Minute provides that the Commission will select work group members based on the nature of the task at hand and the field of expertise and competence; members may include representatives from all levels of government, including local governments. Importantly, these working groups provide additional venues in which stakeholders, including regional residents, scientists, and NGO staff, may collaborate with the IBWC and other governmental organs to advance sustainability of the Rio Grande.
Certain provisions of Minute 331, such as those related to water deliveries, will expire after five years; other provisions, such as the work groups, lack an expiration date. The agreement also calls for the continued negotiation of yet another minute focused on improving reliability and predictability of water deliveries for both Mexico and the United States, with a target completion date of December 2029.
Leadership for Minute 331 was provided by IBWC Commissioners Giner and Resendez over a year and a half of negotiations. Though some of the solutions included in the minute are pilot projects, the completion of the minute indicates that both sides recognize the status quo on the Rio Grande no longer works. Minute 331 delivers some much-needed options to bring change and consistency in transboundary water deliveries. Ideally, this work will continue in 2025 and beyond, building on nearly a century and a half of collaboration over shared waters in the United States and Mexico.