Environment & Science

Colorado River snowpack faring better than Sierra's, but not by much

Glen Canyon Dam at the Colorado River in Page, Arizona.
Glen Canyon Dam at the Colorado River in Page, Arizona.
James M Phelps Jr via flickr Creative Commons

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Southern California typically gets half its imported water from an aqueduct feeding off the Colorado River.

That river relies on a snowpack high up in the Rocky Mountains which is currently about 60 percent of what it would normally be this time of year.

Those numbers aren't great, but they are much better than the anemic Sierra Nevada snowpack, which on Wednesday was found to be at only 5 percent of normal. The news prompted Gov. Jerry Brown to issue an executive order calling for cities to cut water use by 25 percent in less than a year. 

"It's a good thing we have multiple supplies of water coming into Southern California," said Bill Hasencamp, with the Metropolitan Water District. That's Southern California's principal water provider, and it operates a 240-mile aqueduct carrying water from the Colorado to Southern California.

Still, the Colorado River basin has been in a drought for much longer than California.

The last 15 years have seen the lowest average snowpack totals there since records began over a century ago, and two of the main reservoirs storing Colorado River water have been drained to about 40 percent of capacity.

(The map above shows the snowpack levels for the regions of the Rocky Mountains that feed the Colorado River as of April 1st, 2015. Image from the Bureau of Reclamation)

"It takes a long time to get into this drought, and it will take a long time to get out of it," said Hasencamp.

"With increased population and increased demand we might not be able to get ourselves out of it, and what does that mean in the long run?"

Typically, water from the Colorado Rover accounts for about half of the water MWD distributes to Southern California. The rest comes from the northern part of California.

However, Hasencamp said last year, MWD had to get two-thirds of its supply from the Colorado River to meet demand since so little water was coming from the Sierra.

If the drought in the Colorado River basin continues, there may be cutbacks in water allocation to the seven states relying on that resource in the next few years, Hasencamp said.

It's unclear what, if any role man-made climate change is playing in the current water woes, but Hasencamp says many climate models predict the Rockies will see less snow and less rain in the future. And that could mean major changes in Southern California's relationship to water.