The nation’s largest reservoir is drying up.

The last time Lake Mead was this low was in 1937, when it was still being filled after construction of the Hoover Dam, NASA noted in releasing new satellite images this week.

The lake’s elevation has dropped 158 feet since its July 2000 level of 1,200 feet, and now is at 1,042 feet, U.S. Bureau of Reclamation data show. It has not been close to its full capacity of 1,220 feet since 1983 and 1999.

“The largest reservoir in the United States supplies water to millions of people across seven states, tribal lands, and northern Mexico,” NASA said upon releasing the photos this week. “It now also provides a stark illustration of climate change and a long-term drought that may be the worst in the U.S. West in 12 centuries.”

At this time, 74% of nine Western states are in some form of drought, NASA said, with 35% of the area in “extreme or exceptional drought.”

That includes the region surrounding the headwaters of the Colorado River, which feeds Lake Mead and Lake Powell, and is compounded by a below-average snowpack in many places, NASA said.

The images were taken on July 6, 2000, and July 3, 2022, NASA noted. In the latest photos, a “bathtub ring” — mineralized edging around the lake that is normally underwater — can be clearly seen.

The Bureau of Reclamation manages the Colorado River Basin, which also includes Lake Powell farther upstream. That is filled to just 27% of its capacity, and the entire Colorado river system is at 35%, NASA said.

The basin provides power and water to about 40 million people, including those residing in San Diego, Las Vegas, Phoenix, Los Angeles and tribal lands, as well as to 4 to 5 million acres of farmland in the Southwest.

Climate change caused by human activity is exacerbating the natural forces at work, experts say, from recreation — five of six Lake Mead boating launches are closed, NASA said — to daily life.

“Our way of life is already impacted,” Michael Cohen of the Pacific Institute told the Los Angeles Times. “You can certainly argue that people’s lives are changing right now, because of climate change. And a lot of climate change just gets manifested in water, which means hotter, drier, less water available.”

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