The Colorado River’s failure to reach the sea has become a symbol of the Southwest’s water woes. It’s the most heavily developed river systems in the world, with 15 dams along its length and hundreds more on tributaries. This development has created drinking water and power for surrounding communities but has also altered the ecosystem. In the Grand Canyon, after decades of battles between conservationists and developers, land managers have settled on a schedule of regular floods created by releasing water from dams. And they appear to be working.
Three years into the high-flow experiment, or HFE as the U.S. Department of the Interior calls it, the floods in the Grand Canyon are rebuilding sandbars that are important for life along the river. A team of researchers recently detailed the success thus far in Eos, an online news site from the American Geophysical Union.
Back in 1963, the DOI’s Bureau of Reclamation finished the Glen Canyon Dam, just upstream from Grand Canyon National Park. A decade later, scientists determined that the Colorado River’s sandbars and beaches were disappearing. Those river features provide habitat for fish, protect archeological sites and give river rafters a spot to camp. Laurel Morales described the problem for NPR in 2012:
Longtime river guide Brad Dimock has seen those beaches gradually disappear over the years. And where the water level has receded, plants have sprouted.
"The vegetation is on a rampage," Dimock says. "And it's taking over beaches at a pretty high rate of speed, to where it's kind of a war between us and the vegetation in some camps."
The solution, scientists decided, would be to release some of the sediment building up behind the dam in a pulse of water. But those controlled releases from the dams translated to lost revenue for power companies. The first release happened in 1996, the researchers write for EOS, but it’s effects only lasted for about 6 months to a year. Other releases took place in 2004 and 2008.
Backed by data from those floods, in May 2012, the DOI decided that the floods were worth the cost. Here’s coverage of the first flood on May 19 that year:
Brian Clark Howard reported for National Geographic on the second November 2013 flood from the Glen Canyon Dam, where 34,100 cubic feet per second was released for 96 hours. The pulse of water traveled down the canyon in just under a week.
The key to creating the most effective floods is timing, write the researchers in EOS. Remote time-lapse cameras helped scientists figure out how long rebuilt sandbars lasted and what time of year the floods work best. The first three years of decisions on when and how much water to release from the dam have been successful, the researchers write. However, with drought the releases have been getting smaller as the dam engineers hold back needed water. Climate change has also been altering seasonal thunderstorm activity.
Still, they end on a cautiously optimistic note: "Although long-term success cannot be predicted, the early results of HFE attempts to maintain the Grand Canyon’s sandbars show promise."