New Study Finds that Human Activities Resulted in Water Loss from the Colorado River Comparable to Lake Mead in Size.

Posted on: July 26, 2023, 08:27h. 

Last updated on: July 26, 2023, 08:27h.

From 2000 to 2021, the Colorado River Basin experienced a loss of over 10 trillion gallons of water due to human-caused climate change. This amount is equivalent to the entire storage capacity of Lake Mead. A recent study conducted by UCLA has provided the first quantification of the rapid reduction in runoff and confirmed its cause.

The study, published in the journal Water Resources Research, revealed that the Colorado Basin is highly sensitive to warming compared to other major basins in the western US. The study’s lead author, Benjamin Bass, stated, “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.”

Decades ago, this boat sank to the bottom of Lake Mead. In July 2022, the water level at the nation’s largest reservoir — which supplies 90% of Las Vegas’ water — reached its lowest point since it was filled in 1935. (Image: Getty)

According to the study, without climate change, the drought in the Colorado Basin would not have resulted in supply cuts under the first-ever federally declared water shortage. However, Nevada, California, and Arizona agreed to these cuts through 2026 as the drought conditions persisted. The US government is expected to approve the cuts by August.

Though Lake Mead has seen recent rises in lake levels, it’s still far below previous levels. (Image: The Altantic)

The Colorado River Basin supplies water to approximately 40 million people across seven states in the Western US. It also supports agriculture and natural ecosystems. The region has been experiencing the driest period in 1,200 years, with reduced river flow and shrinking reservoirs, leading to concerns about water scarcity as climate change continues.

This study improved upon previous hydrologic modeling by considering changes in runoff due to shifts in vegetation caused by increased atmospheric carbon dioxide. The researchers utilized various data sets to analyze water, vegetation changes, and historical warming in the snowpack regions of the basin. The results demonstrated the significant impact of climate change on reducing runoff and drying out the snowpack regions.

The researchers concluded that if greenhouse gas emissions are not reduced, the decreasing trend in runoff is likely to continue. This presents significant challenges for water managers and highlights the need for adjustments to previous water allocation agreements based on stable regional climate assumptions.

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