On April 28, 2025, the United States announced an agreement with Mexico on the Rio Grande to increase supplies to the United States and reduce the current deficit by October 2025 (i.e., the end of the current cycle).
The 1944 Water Treaty addresses the Rio Grande basin, located south of Fort Quitman, Texas.
The treaty states that the United States is entitled to water from tributaries that feed the Rio Grande into its territory. In addition, it may receive one-third of the flow of certain Mexican tributaries. This volume must average at least 0.35 million acre-feet (MAF) per year, measured in five-year cycles, or 1.75 MAF in total.
The Rio Grande rises in the mountains of Colorado, USA, and runs approximately 3,000 kilometers, forming much of the U.S.-Mexico border from El Paso, Texas, to the Gulf of Mexico.
Rio Grande
Since 1994, Mexico has repeatedly failed to meet its obligations to supply water from the Rio Grande within the five-year cycle. The current cycle began on October 25, 2020, and as of April 19, 2025, Mexico had only delivered about 0.53 MAF, according to CILA.
If there is an extraordinary drought -an undefined term- Mexico must replenish the missing water in the next cycle. Repeated failures have generated concern in Texas and prompted calls for mechanisms to ensure a more reliable supply. The 1944 Water Treaty of 1944 provides for dispute resolution mechanisms in such cases. In April 2025, Trump spoke on social media about possible sanctions and tariffs on Mexico over this issue.
Several experts attribute the recent deficits to the drought in the Rio Bravo basin. In addition, they warn about climate changes affecting weather patterns.
Compliance with the treaty
On April 28, the United States and Mexico signed an agreement. The goal is to increase supplies and reduce the deficit by October 2025.
Over time, Congress has kept a close eye on this issue. In 2024, some Texas lawmakers proposed withholding funds to Mexico to pressure compliance with the treaty.
Now, Congress is evaluating what executive tools are being used. It is also considering whether new legislation is needed in addition to Act 331, passed in November 2024.