Federal officials have started a flood in the Grand Canyon, hoping to restore the ecosystem.
The canyon's ecosystem was permanently changed after the construction of the Glen Canyon Dam in 1963.
The Colorado River downstream used to be warm and muddy, but now it's cold and clear. The shift helped speed the extinction of four fish species and push two others, including the endangered humpback chub, near the edge.
Officials hope the flooding will stir up sediment and redistribute it through the canyon.
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