Misuse of science in the apportionment of the Colorado River’s water in the 20th century led to an overallocation problem that must be addressed. Rules based on overestimation of the available water supply have allowed overuse in the Lower Colorado River Basin and left uncertainty about the obligation of various basin water users to contribute water toward meeting U.S. treaty obligations to Mexico. With a number of key water management agreements expiring in 2026, basin managers have an opportunity to correct the overallocation problems with negotiated agreements that reflect the reality of the river’s hydrology and reduce risks associated with winner-take-all litigation.