Mexico and the United States have agreed new treaty rules on sharing and managing water from the Colorado River.
Under the deal, the US will send less water to Mexico during a drought, while Mexico will be able to store water north of the border during wet years.
The Colorado River flows 2230km from the Rockies into the Gulf of California and serves some 30 million people.
The BBC reports the US and Mexico signed a treaty in 1944 governing the allocation of resources from the Colorado River, which supplies seven states in the US and two in Mexico.
But population growth, increased industry and farming, as well as droughts have since put pressure on the river.
The latest accord runs until 2017.
