A Border Patrol agent waits for a patrol boat at the Rio Grande, Thursday, Feb. 13, 2025, in McAllen, Texas.. Water levels are low because Mexico owes the U.S. water under a 1944 international treaty.

The Rio Grande Compact—signed in 1938 between Colorado, New Mexico and Texas—sealed the river’s fate. The compact ensured that farmers in all three states would get their share of water.