Colorado River Basin Has Lost As Much Water As the Size of Lake Mead

The Colorado River Basin has lost as much water as the size of Lake Mead over the past 21 years.

A new study from the American Geophysical Union (AGU) found that climate change caused the loss of over 40 trillion liters of water from the basin from 2000 to 2021.

This is about the same full capacity of Lake Mead, which is the largest man-made reservoir in the United States, stretching over the Nevada-Arizona border.

The Colorado River provides water for 40 million people living in the basin areas, which are Arizona, parts of California, New Mexico, Colorado, Utah, Nevada, and Wyoming, and two Mexican states—Baja California and Sonora.

And river levels are the lowest they have been in a century. This is largely due to climate change caused drought gripping the region.

The study, published in the AGU journal Water Resources Research, reported that without climate exacerbating the effects, reservoir levels would likely not have dropped to such low capacities in 2021.

Reservoirs like Lake Mead are in a dire state due to the drought. And while the reservoir has filled slightly this year due to heavy rainfall, it still reached its lowest point ever in summer 2022, of 1040 feet below sea level. The reservoir has not seen levels this low since it was first constructed in the 1930s.

"While we knew warming was having an impact on the Colorado Basin's water availability, we were surprised to find how sensitive the basin is to warming compared to other major basins across the western U.S., and how high this sensitivity is in the relatively small area of the basin's crucial snowpack regions," Benjamin Bass, a hydrologic modeler at the University of California-Los Angeles and lead author of the study said in a press release.

"The fact that warming removed as much water from the basin as the size of Lake Mead itself during the recent megadrought is a wakeup call to the climate change impacts we are living today."

Although there has been a lot of research focusing on the water crisis of the southwest, there hasn't been much insight into the effects of the increased carbon dioxide in the atmosphere.

The Colorado River feeds off snowmelt running down from the mountains. As the drought makes weather patterns harder to predict, there has not been enough to replenish the river in recent years, paired with overconsumption of water across the southwest.

This new study has assessed how atmospheric changes have affected the runoff. It is also the first research to assess the runoff changes per degree of warming. They compared historical warming data in the Colorado Basin snowpack region.

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