The money is split among three projects benefitting the Gila River Indian Community.
Officials said $83 million would go toward a reclaimed water pipeline that will run to the reservation from Mesa. That pipeline is scheduled to be completed in 2024.
Another $150 million over three years will support water conservation efforts within the tribe, expected to save 125,000 acre-feet of water per year.
Federal officials said they expect those conservation programs to leave an additional two feet of water elevation in Lake Mead, which supplies water to much of the Southwest.
Gila River Indian Community Governor Stephen Roe Lewis said a third project will cover the reservation canals with solar panels to minimize evaporation.
The West is currently in a record-breaking 23-year megadrought.
Lake levels at Lake Mead have been falling for decades, stressing the ability of the Colorado River system to provide water for New Mexico, California, Nevada and Arizona.
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