The West's historic drought is threatening hydropower at Hoover Dam

The West's historic drought is draining Lake Mead, and the lower it gets, the less hydroelectricity Hoover Dam can produce.

(CNN)Standing atop the Hoover Dam today, the millions of tourists who visit each year can get a real sense of the climate crisis in the West: In addition to extreme heat, the sight of so-called "bathtub rings" that envelop Lake Mead has become an unsettling reminder of where the water level once was before the region's historic drought began.

The changes are "stunning to see," Kristen Averyst, senior climate advisor for Nevada Gov. Steve Sisolak, told CNN. "If people don't think that climate change is impacting them here and now, just go to Lake Mead and have a look around, because that paints a pretty clear picture of what we're up against when it comes to climate change."
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The West's historic drought is threatening hydropower at Hoover Dam

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Stretching across the Colorado river at the Nevada-Arizona border, the enormous Hoover Dam forms and holds back water from Lake Mead -- the largest manmade reservoir in the country. It can produce around 2,080 megawatts of hydropower -- enough electricity for roughly 1.3 million Americans each year, according to the National Park Service -- for California, Arizona and Nevada as well as Native American tribes.
      But the climate change-fueled drought and overuse of the Colorado River's water is pushing Lake Mead lower and threatening the dam's hydroelectricity production. Declining water flow has cut the dam's power generation capacity almost in half -- around 1,076 megawatts -- as of June.
        The water elevation in Lake Mead is around 1,040 feet above sea level. At 950 feet, Hoover Dam will be at its lowest point to be able produce power, according to the US Bureau of Reclamation. Without the dam's electricity, Southwest energy suppliers will have to look to fossil fuel energy to fill the void.
          It's one unprecedented challenge among many facing officials at the US Bureau of Reclamation, which manages Hoover Dam operations, as the West runs out of water.
          US Bureau of Reclamation commissioner Camille Touton emphasized in June testimony to Congress that despite the agency's ongoing efforts to conserve water, much more needs to be done as climate change puts a strain on the Colorado River system.
          "The system is at a tipping point," Touton said in her statement. "No amount of funding can completely offset the severe shortfalls in precipitation being experienced this year across the American West. We will experience unavoidable reductions in farm water supplies and hydropower generation."

          'Dead pool'

          Averyst vacationed at Lake Mead growing up -- wakeboarding and waterskiing there were some of her favorite activities. Her great-grandfather was even one of the workers that built the dam, she said, which was completed in 1934. Its iconic U-shape, almost as thick as two football fields are long, became a symbol of Americans' hard work during the Great Depression.
          But the lake is not the same as it used to be, she said. As water drains, more muddy shoreline appears. "The way I characterize it is, it's not shaped like a regular glass, it's shaped like a martini glass," Averyst said, so the lower the lake gets, the faster the shoreline recedes.
          The "bathtub rings" along Lake Mead near the Hoover Dam that show how far the lake has fallen.
          The receding water means it's an hours-long wait just to put a boat on the lake due to all the closed boat ramps and docks. Previously sunken boats are exposed on the newly bare shoreline. A decades-old intake valve, a World War II-era vessel and human remains have shockingly emerged from the depths.
          The Bureau of Reclamation predicts there is a 1-in-5 chance the lake could fall to 1,000 feet by 2025, which is only 50 feet above the minimum level needed for Hoover Dam to generate electricity. And it's just 105 feet above the lake's dead-pool level -- the point at which water won't flow freely through the dam and generate power. Instead, power would be needed to pump water through the dam.
          "We have already seen the power generation at Hoover Dam decrease about 30 to 40% from its maximum capability over the past 10 years," John Jontry, manager of power operations and planning with the Metropolitan Water District of Southern California, told CNN.
          Jontry's agency gets roughly 1 million megawatt-hours of electricity each year from Hoover Dam, which it uses to help power the pumps along the Colorado River Aqueduct to deliver water from Lake Havasu -- a reservoir on the Arizona-California border -- to Southern California.
          The Hemenway boat ramp at the marina on Lake Mead.
          A formerly sunken boat on Saddle Island in Lake Mead.