Hoover Dam has recent source-backed changes around The U.S.’s Largest Reservoir Just Fell to Its Lowest Water Level and Lake Mead, the Nation’s Largest Reservoir, Is Smaller Than Ever.
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Boats cruise past a white "bathtub ring" of mineral-stained rocks left by higher water levels in The Narrows upstream of the Hoover Dam in the Lake Mead National Recreation Area on July 25, 2026. —Ethan Miller—Getty Images Lake Mead, the reservoir on the Arizona-Nevada border that is a crucial source of water for the A.
Water levels in the reservoir, which sits behind the Hoover Dam, are at record lows. A continued drop would imperil water supplies for millions of people and cut electricity from the dam.