Lake Mead is North America's largest man-made reservoir. It can hold up to 28,945,000 acre-feet of water at one time, and is formed by the legendary Hoover Dam.

The reservoir is integral to the surrounding areas, with some 25 million people relying on water from Lake Mead.

So where does it get its water from?

Lake Mead lies on the Colorado River, between Nevada and Arizona.

It also gets its water from three smaller tributaries, the Virgin and Muddy rivers and the Las Vegas Wash.

The Virgin and Muddy rivers flow into the Overton Arm. From there and they eventually merge with the rest of the Colorado River. The Las Vegas Wash enters Las Vegas Bay—which is at the western edge of Lake Mead—from the Boulder Basin.

The Colorado River itself is fed by snowpack runoff coming from the Rockies. It flows for 1,450 miles, all the way to the Gulf of California.

The water held in Lake Mead is then irrigated by Hoover Dam. The dam also uses the water flow to produce hydropower.

The Colorado River as a whole, provides water to over 40 million people living in the basin states.

The Colorado River basin is made up of all of Arizona, parts of California, New Mexico, Colorado, Utah, Nevada, and Wyoming, and two Mexican states—Baja California and Sonora—although the final two states contribute little runoff to the river.

But the Colorado River, and subsequently its reservoirs, are not what they once were. The basin states have been affected by a megadrought that has gripped the southwest of the U.S. for two decades.

The Colorado River's water levels are now the lowest they have been in a century, and Lake Mead is at just 30 percent of its full capacity.

Andrea Achilli, an associate professor of the Department of Chemical and Environmental Engineering at the University of Arizona, told Newsweek: "Prolonged drought and over-allocation have dramatically reduced the amount of water in the Colorado River and the stored water in Lake Mead and Lake Powell. They are the largest reservoirs in the US and are essential to the management of the Colorado river basin. We are experiencing the driest conditions in the last 1,200 years."

Is Lake Mead filling up?
Lake Mead's water levels are in a dire state. In July 2022, the lake reached a historic low of 1,040 feet above sea level. This was the lowest water levels have been since the lake was first constructed in the 1930s.

Lake Mead's water levels were 1,047.38 feet as of February 23. The level has risen over the winter months due to rainfall and particularly cold weather to hit parts of the U.S.

But while Lake Mead has filled up slightly since its low point of July 2022, the Bureau of Reclamation anticipates that the water levels will start to decline again come spring.

A Bureau of Reclamation study published in January predicted that Lake Mead could reach a new all-time low in 2023. It projected water levels could reach 1,024.47 feet by November.

This is because, despite recent rainfall, the region is still in a severe drought. The dry conditions, paired with the overconsumption of water in the region, means that the lake will continue to dry up faster than it can replenish itself.

"As a result, in 2023, Arizona will reduce its Colorado River supply by 592,000 acre-feet, corresponding to 21 percent of the Arizona Colorado river supply and approximately 9 percent of Arizona's total water supply. The agricultural sector is the most impacted user," Achilli said.

"There is a need for a portfolio of solutions to manage water in the Southwest and to provide a sustainable future. Conservation may be a short-term solution, but in the middle and long term, we need to look at new water sources to augment supply. In my opinion, water reuse needs to be vigorously pursued, as it is a multiplier of the water available while reducing stress to the environment. For example, we have the opportunity to transform our cities into net zero urban centers with careful planning and appropriate reuse technologies."

It is not just Lake Mead that needs attention from policymakers. Lake Powell, another Colorado River reservoir formed by the Glen Canyon Dam between Utah and Arizona, is also drying up due to the drought.

"The first thing that comes to my mind that is often overlooked is that these two reservoirs produce electrical energy for approximately one million homes, so there will be a scramble to find an alternative source of power for A/C and the other many uses," Achilli said.

"Water and energy are intimately linked, and the water stress in the Colorado River basin is also increasing the stress in the power sector. It is a dangerous combination when there is increasing power demand during the summer months due to increasingly hot summers and a reduced supply due to persistent drought conditions that limits the water available."