A paddleboarder floats by Lone rock on Lake Powell on March 29, 2015 near Big Water, Utah. Lake Powell is part of the Colorado River Basin.

(Justin Sullivan/Getty Images)

At a Glance

The Colorado River has experienced a 7-percent decline in water flow over the last 30 years, according to a new USGS study.It's believed that warmer temperatures are the main reason for this decline.One-third of Southern California's drinking water comes from the Colorado each year.

One of the West's key water sources has been in serious decline in recent decades, according to a new study from the U.S. Geological Survey.

The findings, , revealed a 7-percent decline in the Colorado River's flow over the last 30 years. The main reason for the increased evaporation is simple: climate change is causing temperatures to rise, and the warmer weather is sucking more water into the atmosphere, the study added.

The news is especially concerning for Southern California, where one-third of the drinking water used annually comes from the Colorado River. If you add up all the water lost to the river's decreased flow, that equals about 24 percent of the amount of water pulled annually from the Colorado in California.

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"These are pretty significant amounts that are being lost ," Gregory McCabe, a climate scientist with the USGS and lead author of the study, told KPCC.

KPCC also noted how crucial the Colorado's water was during the recent five-year drought that yielded severewater restrictions in California. With so little Sierra snowpack to melt and flow downstream, the southern half of the Golden State relied on the Colorado River for much of its water.

In addition to the warmer temperatures, previous studies have also blamed dust that has blanketed Rocky Mountain snow, which causes the snowpack to absorb more sunlight and melt faster, as well as thirsty invasive species that reside along the river and drink large amounts of the water, KPCC added.

Now, the ugly trend along the Colorado River has experts concerned that future California droughts will be even more difficult to overcome.

"What I'm saying to folks in Southern California is, 'Watch out,'" Brad Udall, a water and climate researcher with the Colorado Water Institute at Colorado State University, told KPCC. "Were Colorado River reliability to go down, it would mean that droughts like the one you just went through might not be so easy for urban areas in Southern California."