California and Nevada have had extremely heavy rainfall in recent days, during one of the severest droughts the region has ever seen.

So what does that mean for the water levels at Lake Mead?

Lake Mead’s water levels are rapidly declining due to the drought. The reservoir—which stretches across Nevada and Arizona, on the Colorado River—is relied upon by 25 million people living in the region. It’s formed by the Hoover Dam, which generates electricity for the surrounding communities.

During the summer, the lake’s water levels hit a new low at 1,040 feet—this was the lowest since its construction in the 1930s.

Experts predict that in a few years, the lake’s water levels could be as low as 895 feet, which would be too low to flow past the dam.

So, the rain has undoubtedly been a welcome water source for the lake. And Lake Mead’s water levels are currently 0.3 percent higher than originally predicted in December, the Bureau of Reclamation said, according to a News Now report.

Lake Mead and Rain
File photos of Lake Mead and heavy rainfall. Rain in the region has lifted its water levels recently.
bloodua / Julia_Sudnitskaya

Since the beginning of December, the reservoir’s water levels have steadily increased. As of December 1, the water levels stood at 1,042.97 feet. By January 18, Lake Mead’s water levels have risen to 1,045.76 feet.

The lake is now at 28 percent its usual capacity, while during the summer it was only at 27 percent.

But even though the water levels have risen, this isn’t likely to help the lake in the long term. Experts believe only a change in water policy can contribute to saving the lake.

Dr. Joellen Russell, a climate scientist and professor at the University of Arizona and member of the group Science Moms, told Newsweek: “Lake Mead is more than 180 feet below its “full level” and hasn’t been close to full since 1999. It would take several years of much-above average snowpack (unlikely given the warming temperatures), combined with drastically less water usage to let Lake Mead begin to fill again.”

Lake Mead doesn’t just rely on rainfall for its water, but snowpack that flows down through the mountains.

The drought in the Western U.S. has been ongoing for two decades. As it continues, weather patterns are becoming harder to predict, meaning people are using the water faster than it can be replenished.

As the drought has gone on for so long, despite the rain giving respite to Lake Mead’s water levels, it will take a lot more wet weather to fix the problem.

Jennifer Pitt, the Colorado River program director with the National Audubon Society, an environmental organization, previously told Newsweek: “To refill the Colorado River reservoirs, you would need three average years of snowfall without any water use.”

“There’s been a good start to the snowfall season, but it is way too early to know what runoff will look like. Today the water uses allowed by law are more than the river gets in an average year, so until the rules are changed it is unlikely the reservoirs will fill.”

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