The city of Phoenix has outlined what it will contribute voluntarily to a regional plan to shore up a reservoir that delivers Colorado River water to three states and Mexico.
The river already can't provide seven Western states what they were promised a century ago.
Phoenix, the nation's fifth largest city, is among entities that will pitch in to fulfill the so-called 500+ Plan.
City officials say they'll leave some water in Lake Mead that straddles the Arizona-Nevada border instead of storing it underground as planned.
The plan will be implemented as Arizona, Nevada and Mexico are forced to endure their first-ever mandatory cuts from the river.