Wednesday, February 3, 2010

Flooding the Big Ditch

As a sometimes canyon boatman, I'm quite interested in the result of the 2008 flooding experiment. Well, the results are in, and they're a mix of positive and negative:

The experimental flood of March 2008 in the Grand Canyon has yielded two main findings: The high water worked well in building sandbars as hoped, but they weren't lasting.

The flood released twice as much water as normal down the Colorado River for 60 hours that spring, and it created large stockpiles of sand that had accumulated in a few major tributaries.

Researchers with a branch of the U.S. Geological Survey in Flagstaff say the flood was successful in expanding the sandbars used by river runners for camping, which also form backwaters that possibly help young and endangered fish survive.

It's something of a hot issue because these beaches have been shrinking in recent years, and vegetation has been spreading over much of what remains, making camping less available.

"By October 2008, six months after the high-flow experiment, the new sandbars had been largely eroded by typical fluctuating-flow dam operations," researchers wrote in a brief paper.

Releases from the dam are increased and decreased, within limits, to meet hydropower demands from customers in six states.

The bigger question is whether the Colorado River system through the Grand Canyon can be kept static or gain sand instead of continuing to lose its beaches and sandbars.

"It may not be possible to rebuild and maintain sandbars over the long run solely through the manipulation of Glen Canyon Dam operations," the researchers posit in a fact sheet on the subject.

That's because about 90 percent of all sand that once flowed through the Canyon now winds up behind Glen Canyon Dam, said Ted Melis, deputy chief of the Grand Canyon Monitoring and Research Center at USGS.

Similar to the results of the flooding of 1996 and 2004, the benefits are only temporary. Which points to the need to repeat the floodings in order to maintain a healthy ecosystem in the Grand Canyon.

And I'm hoping to get my raft there this spring for a personal inspection.


Fearguth said...

Although I've hiked and backpacked in the Canyon many times since 1973, I've floated the Colorado River through the Canyon only once, in April, 2007. Needless to say, it was an unforgettable experience.

I will make my next journey to the Grand Canyon in late March for a couple weeks of camping and hiking. I can hardly wait.

pygalgia said...

If you find yourself stopping in Flagstaff, let me know. Be happy to meet up.