Even tribes, which hold the most senior water rights in the state, are concerned about the federal government’s doomsday situation.
Members of the Ak-Chin Indian Community, who use Colorado River water to grow barley, potatoes and corn on 16,000 acres south of Phoenix, are not sure how that water would be delivered if the Central Arizona Project lost its entire allotment.
The uncertainty has reopened old wounds. In the 1970s, after failing to prevent nontribal farmers from draining an aquifer below the Ak-Chin reservation, Congress passed a law to ensure the tribe would always have an alternative source.
“It’s deeply concerning if this promise to us will once again be broken,” said Gabriel Lopez, the tribe’s chairman.
The tribe, whose name refers to traditional irrigation methods, has tried to conserve, Mr. Lopez added, and its farms now mostly use more efficient sprinkler systems.