Several southwestern states and Mexico are nearing a water sharing agreement regarding the Colorado River. The agreement would share the surplus water stored in Lake Powell and Lake Mead along with a water shortage burden felt more harshly the further south the water travels.

The new agreement would serve multiple purposes for Mexico. Since 2010 when an earthquake damaged their irrigation system, Mexico has stored portions of their water supply in Lake Mead. The new agreement extends their ability to do so as the continue to make repairs. Additionally the agreement includes environmental considerations that should replenish the water supply in the Colorado River Delta, which has run nearly dry.

The agreement will act as an addendum to the 1944 US-Mexico Water Treaty that allocates freshwater resources between the two countries. The Treaty is particularly important because the border between the United States and Mexico is made up of two-thirds water boundaries. The Colorado, Tijuana, and Rio Grande Rivers create a border and a finite supply of freshwater to growing demand on both sides of the border.

The new agreement directly affects Southern Californians and San Diegans as the Metropolitan Water District of Southern California will pay $5 million per year for 47,500 acre-feet of water. The Metropolitan Water District and the San Diego County Water Authority are locked in litigation regarding the rate structure that the Metropolitan Water District uses to charge San Diegans.

An increase in freshwater supply to the district may affect the outcome of the litigation and change the water rate structure in San Diego County.

The Mexican-American agreement could be the most significant changes on the Colorado River since the 1944 Colorado River Compact that allocates water entitlements between States. The negotiation process has lasted for seven years and the agreement is expected to be signed next week at Morelos Dam in Mexico.