Lake Mead is the largest reservoir in the United States, but Lake Mead is low, and that has some folks worried.

Lake Mead was formed by the Hoover Dam, and sits between Nevada and Arizona. It is 112 miles long and supplies water to much of the Southwestern United States.

Lake Mead is nearing an all-time low. While that may sound shocking, it should also be noted that Mead has not been at full capacity since 1983, partly due to water demand, but also due to climate and weather factors.

What happens if Mead continues to go low? Might some water deliveries end up stopping?

“The first thing you would do is you would stop agriculture deliveries,” Bob Barrett, a spokesman for the Central Arizona Project said. “You can stop growing cotton but you can’t stop growing people. Agriculture would have to go back to groundwater.”

Arizona has been storing water underground, and could continue to make deliveries for some time.

“We would start extracting the water we’ve been storing underground, put it into the canals and make our deliveries,” Barrett said.

#Vegas is almost out of water. Apparently what happens in Vegas, doesn't always stay in Vegas! #Lame #VivaBrazil

— Sanjay Burman (@BurmanBooks) July 8, 2014

Scientists studied the potential effect of low levels in Lake Mead back in 2008. One study from Scripps Institution of Oceanography, at UC San Diego reported that there is a 50 percent chance Lake Mead, a key source of water for millions of people in the southwestern United States, will be dry by 2021 if climate changes as expected and future water usage is not curtailed.

“We were stunned at the magnitude of the problem and how fast it was coming at us,” said physicist Tim Barnett. “Make no mistake, this water problem is not a scientific abstraction, but rather one that will impact each and every one of us that live in the Southwest.”

“Today, we are at or beyond the sustainable limit of the Colorado system. The alternative to reasoned solutions to this coming water crisis is a major societal and economic disruption in the desert southwest; something that will affect each of us living in the region,” the report concluded.

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