The United States on Thursday said it denied an urgent request made by Mexico for water to be delivered to Tijuana under a 1944 water-sharing treaty between the two nations, with the United States blaming Mexico for “decimating American agriculture – particularly in the Rio Grande Valley.”

The move highlights the complicated and stressful relationship the two nations have through water-sharing agreements with the Colorado River and Rio Grande Basin, and how the effects of climate change are playing into water disputes.

Mexico made a request for a special delivery of water from the Colorado River to be delivered to Tijuana, the U.S. State Department’s Bureau of Western Hemisphere Affairs said in a post on X. The Treaty of February 3, 1944 calls for Mexico to deliver water from rivers that form the Rio Grande Basin to the United States, which in turn sends Mexico water from the Colorado River.

In recent years as surface and groundwater supplies shrink from warming southern regions, Mexico has fallen behind in its water obligations under the treaty. Last year the Rio Grande Valley Sugar Growers, Texas’s only sugar mill, closed and blamed a lack of water that came through Mexico’s compliance with the 1944 water treaty for halting operations after 51 years.

“Mexico’s continued shortfalls in its water deliveries under the 1944 water-sharing treaty are decimating American agriculture – particularly farmers in the Rio Grande Valley,” the State Department’s Bureau of Western Hemisphere Affairs said in its X post. “As a result, today for the first, the U.S. will deny Mexico’s non-treaty request.”

Mexican President Claudia Sheinbaum told reporters in Mexico, “there’s been less water. That’s part of the problem.”

She said the water issue was being worked through by the International Boundary and 

Water Commission. The little-known agency handles any disputes involving the water compacts and controls the flow of water through the management of water gates.

In November of 2024, the United States and Mexico reached an agreement on how to improve delivery of water under the 1944 water treaty to address Mexico’s problems. It took 18 months of negotiations to reach a deal.

In April the Rio Grande Compact Commission will hold its 86th annual meeting in Alamosa.