By Karen Morfitt

DENVER (CBS4) – Often called the hardest working river in the West, the Colorado River supports seven states, 30 tribal nations and Mexico. According to American Rivers, a national river conservation organization, it is also now the most endangered river in the United States.

(credit: CBS)

“The river flow is now down 20% in the 21st century,” Brad Udall said.

Udall, a Senior Climate and Water Research Scientist at Colorado State University, has studied the river for more than two decades.

That decline will impact all of the nearly 40 million people the river serves. In the upper basin, farmers and ranchers are seeing wells dry up, and in the lower basin two of the country’s largest reservoirs, Lake Powell and Lake Mead are quickly being drained.

“There are a whole series of ramifications and impacts on people depending on where you are, but if you use water — and that means everybody in the American West — you’re probably going to be impacted in some form or another as this continues,” Udall said.

The Colorado River wraps around Horseshoe Bend on March 30, 2015 in Page, Arizona. (Photo by Justin Sullivan/Getty Images)

According to the “Colorado River Report” by American Rivers, there are two major threats to the Colorado River: outdated water management and climate change.

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“What the warming and drying of the basin is doing is it’s increased evaporations. What it means is a normal snowpack like last year which was 90% of normal, that 90% normal snowpack turns into 30% of runoff,” he said.

So, what can be done? The report suggests putting more federal funding toward climate resilient projects. Sen. Michael Bennett, while touring the devastation left behind by the Marshall Fire in Boulder County, says it’s an issue he plans to take back to Washington.

“These fires and these floods and the fact that the Colorado River is basically empty at this point means that there’s a lot of work to do,” Bennett said.

Take a look at the full report.

Karen Morfitt