Federal water managers simulate flooding flows in Colorado River
By Summit Voice
SUMMIT COUNTY — Water may be in short supply in the West this year, but that didn’t stop federal officials from cranking open the valves of Glen Canyon Dam to unleash what’s unromantically being called a high-flow experimental release. The release won’t change the overall water balance in the Colorado River system, as adjustments are made at other times.
The five-day high-flow regime will lower Lake Powell by up to 2.5 feet in just a few days and send more than 42,000 acre feet of water surging through Glen, Marble and the Grand Canyon before it ends up Lake Mead. A detailed FAQ is online here.
This year’s release is the first since 2008 and is intended to rebuild depleted sandbars and beaches. Under the concept of high flow experimental releases, sand stored in the river channel is picked up by high-volume water releases from the dam and re-deposited in downstream reaches as sandbars and beaches.
These sand features and associated backwater habitats can provide key fish and wildlife habitat, potentially reduce erosion of archaeological sites, restore and enhance riparian vegetation, increase beaches, and enhance wilderness values along Colorado River in Glen Canyon National Recreation Area and Grand Canyon National Park.
High-flow experimental releases are designed to mimic the natural flooding of the Colorado River through Glen and Grand canyons that occurred prior to the construction and operation of Glen Canyon Dam.
Nearly all the natural sediment load once transported by these floods is now trapped behind the dam resulting in the loss of downstream sandbars, beaches, and associated resources critical to the ecosystem health along the Colorado River corridor in Grand Canyon National Park and Glen Canyon National Recreation Area. Episodic floods from tributaries downstream from the dam, such as the Paria River, are critical sources of sand input and the Department of the Interior anticipates that high flow experimental releases will benefit downstream resources when conducted under sediment rich conditions.
“The water released this week is the first in a long term plan that will help to build new camping beaches in the Grand Canyon, and ultimately, will improve the canyon experience for boaters supporting a $26 billion recreation economy that depends on the Colorado River,” said Protect the Flows member George Wendt.
“We applaud the Department of Interior for taking these important steps that take into consideration the long term use of the canyon by boaters. his release shows an attempt at good stewardship of the area and is an example of how the conservation community and those who love to recreate on the river worked together with the Department of Interior on a solution that both fish and rafters will benefit from for years to come.”
“Grand Canyon beaches are in a constant state of erosion, so replenishing the beaches is vital not only to Grand Canyon rafting, but more importantly to the Grand Canyon ecosystem as a whole,” said Alexandra Thevenin, genera manager of Arizona Raft Adventures & Grand Canyon Discovery. “That includes promoting native vegetation and backwaters, which in turn supports many native species. We love it when the Adaptive Management works.”
Executive summary from the EIS on the high flow experiment: