Colorado River After the Pulse Flow

Posted by Jeff on Feb 7, 2015 @ 9:19 am in Conservation | 0 comments | Last modified: February 7, 2015

In 2014 there was an agreement between the U.S. and Mexico that allowed for the release of water into the Colorado River Delta. Known as a pulse flow, it lasted from late March to mid-May last year. Scientists have now returned to the path of the historic pulse flow, a release of water designed to rejuvenate the delta that has been totally dry for decades.

By all accounts, the pulse flow’s most important outcome is that it actually happened. For so long, the forces against it seemed overwhelming. With western water such a scarce commodity, and so many entities drawing water from the Colorado River, a bi-national agreement seemed unlikely to gain any traction. But against these odds, an agreement was forged.

More than 105,000 acre-feet of water (equal to 34 billion gallons) was released in one large pulse flow between March 23 and May 18, 2014. That’s less than one percent of what would naturally flow into the delta without all the upstream diversions. Since it came as such a big surge over such a short time, the river channel and floodplain were inundated. Cottonwood and willow seeds filled the air. To everyone’s surprise and delight, the pulse flow temporarily re-connected the river with the Gulf of California.

Success was even beyond expectations. The pulse flow benefited existing vegetation throughout the surrounding area, well beyond designated restoration sites. There was a 43% increase in green vegetation in places the pulse flow inundated, and a 23% increase in the broader riparian area. Bi-national negotiations for another agreement will begin soon.

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