Lake Mead, America's largest reservoir, has sunk to its lowest level in history, pushing 40 million people who depend on it closer to a water and power crisis.
The reservoir, which stretches along the Colorado River between Nevada and Arizona, has lost 180 feet of water over the past three decades as repeated droughts have starved it of the water needed to replenish it. It now stands below 1,040 feet above sea level, edging closer to levels that could cripple electricity production at Hoover Dam.
AccuWeather Senior Meteorologist Chad Merrill called the extreme drought "the tipping point" in a decades-long cycle of dry weather across the West, warning that water shortages and power problems are now almost unavoidable.
Water cuts have already begun. The US Bureau of Reclamation, which manages the nation's dams and reservoirs, has signed off on a plan to cut water usage from the Colorado River by 20 percent in Arizona, California and Nevada through 2028.
"At least through the fall season, there's still going to be significant shortages of water," Merrill told the Daily Mail. "The hope is there's a much better winter than last winter was, but this will likely continue to be a problem even by this time next year."
The Colorado River supplies drinking water and irrigates farms across seven states, while also feeding Lake Mead behind Hoover Dam and Lake Powell behind Glen Canyon Dam.
Wildlife and flash flood risks
Merrill said the worsening drought could bring further harm, warning that wildlife across the region may become more aggressive toward residents as animals search for dwindling food and water.
He also fears that when rainstorms do arrive later this year, fueled in part by a recently formed El Niño in the Pacific, the ground will be so hardened by drought that it cannot absorb the water, potentially triggering flash floods that catch residents by surprise.
"Even though we've been dealing with a long-term drought, there's still the possibility of flash floods. When you have very high rain rates over very dry ground, that can produce flash flooding," Merrill said. "So, for those folks out west, just make sure that you practice your flash flood plan, just like folks in the Midwest practice their severe weather plan when we get into the spring season."
A decades-long drought cycle
The Colorado River Basin has been cycling in and out of droughts since 2000, the same year Hoover Dam was near its capacity of 1,220 feet above sea level. Merrill said conditions reached their worst point between 2020 and 2022.
"That's when we saw the highest level of that significant drought. Now, since then, there's been very little recovery, and as it stands now, there is obviously significant drought, and water levels are declining," he said. "To get the water levels as low as they are takes consistent dry weather over an extended period of time."
That has included an extreme decline in snow this past winter in the Rocky Mountains, the source of the Colorado River, which relies heavily on melting snow to replenish the river and its lakes each year. Merrill said a persistent La Niña, a weather pattern that strengthens the polar jet stream and weakens the subtropical one, cutting off moisture to the Western US, significantly contributed to the 2020-2022 drought. Earlier droughts struck the region in 2018 and again from 2002 to 2004.
Turbines nearing shutdown
As of August 24, Lake Mead stood at just 1,039 feet above sea level, less than five feet above the point at which Hoover Dam's 12 older turbines would be taken offline to prevent severe cavitation damage.
That would leave only five newer wide-head turbines running, sending the dam's generating capacity plunging from roughly 1,274 megawatts to just 382 megawatts. Hydroelectric production would stop entirely if the reservoir fell below 950 feet.
At Lake Powell, the situation is just as dire, with water levels only 30 feet from shutting down all hydroelectric production there.
For the nearly two million people who get electricity from these dams, a shutdown would mean state officials must draw power from other sources, such as natural gas, raising utility bills. It would also strain electrical grids already taxed by extreme heat and humidity across the country this summer, including repeated bouts in the Southwest.
Heat feeding the drought
The same extreme heat driving up electricity demand is also accelerating evaporation from the reservoirs that help supply that power, creating a feedback loop across the West.
"That is one contributing factor to the dryness, because the evaporation from Lake Mead and Lake Powell has been exceptionally high this summer, because the heat dome has been centered across the western US," Merrill said. "Even though there have been sporadic thunderstorms, because of the heat, because the heat's been pretty persistent... a lot of that moisture evaporates before it can actually settle into the soil."
Heat domes, high-pressure systems that trap hot air and humidity near the ground, have produced record temperatures across the US this summer. Las Vegas and Phoenix have seen daily temperatures near 120 degrees Fahrenheit.
What comes next
El Niño, which has the opposite effect of La Niña, is expected to bring rainfall to the western US through next year, but Merrill said it will take far more than one wet winter to undo the damage along the Colorado River.
"The magnitude of it might lessen a bit, but there's still going to be some water shortages, most likely. There would have to be multiple back-to-back seasons with above-average precipitation to actually fill the reservoirs quite a bit," he said.
The August 21 announcement from the Bureau of Reclamation showed Arizona would see the biggest cuts among the three affected states, and larger cuts could follow in 2027 and 2028 if the crisis at Hoover Dam worsens. Merrill predicted demand for Colorado River water would only grow in the near future, with little relief expected heading into 2027.
A July report from the Bureau of Reclamation projected Lake Mead could drop another 33 feet over the next two years. The reservoir is currently operating at less than 27 percent capacity.
