Top Interior Department officials, with an eye toward restoring some semblance of natural rhythms to Grand Canyon National Park, on Wednesday announced plans to resume high-flow releases from Glen Canyon Dam into the Colorado River.
In years past such releases, designed to transfer heavy sediment loads from Lake Powell into the Colorado to help rebuild beaches and improve habitat for native fishes, have been a point of contention between the National Park Service and the U.S. Bureau of Reclamation. While the Park Service desires to see seasonal ebbs and flows to the Colorado restored, something the Glen Canyon Dam has blocked, Bureau of Reclamation officials have been more concerned about power generation from the dam.
During a conference call Wednesday, Interior Secretary Ken Salazar and his assistant secretary for water and science, Anne Castle, said a protocol had been signed off on that provides for occasional high-flow releases over the course of the next eight years. These flows will reach 31,500-40,000 cubic feet per second and last anywhere from one to 96 hours.
“The high flow releases that have been studied and are the subject of the protocol will go from today through 2020," said Assistant Secretary Castle. "They can occur during particular times of the year, specifically March and April or October and November, and they can occur when the sediment conditions, the triggering conditions, are favorable in the river.
"So we don’t know exactly how many high-flow experiments will be able to be done over that eight-year period," she added. "It just depends on what the conditions in the river are like."
The announcement was applauded by the Grand Canyon Trust, where Nikolai Lash, the group's Water & State Trust Lands Program director, said the flows would be a great help to the canyon.
“We’re all excited that it passed muster finally," said Mr. Lash. ‘“Now they have legal compliance to run high flows when they’re well-triggered.”
Flows upwards of 45,000 cfs through the Glen Canyon Dam carry lots of sediment that is placed high up on the canyon's shores, he explained. "That’s how you get the built-up beaches and you get the sediment for rebuilding the shoreline, and the backwaters for rearing native fish," added Mr. Lash.
Regular flows through the dam, below 30,000 cfs, more often perform a scouring effect, erode beaches, and dump the sediment in Lake Mead downstream, he said.
Back in December 2009 the Interior secretary stated his desire to see more high-flow releases through the Grand Canyon, adding his belief that they could be done to benefit the national park's resources while also meeting energy and water needs. On Wednesday he repeated that belief.
The approach that has been designed will ensure the delivery of “water to communities, agriculture, and industry, and provide clean hydro-electric power," Secretary Salazar said. "... In addition to that, the second goal, is to make sure we’re protecting one of the world’s most treasured landscapes, the Grand Canyon.”
The releases are needed, said Assistant Secretary Castle, because the dam prevents sediments from flowing on downstream through the Colorado River where they can be beneficial to the canyon.
"The Colorado River got its name from the Spanish word for red, and it was named for the heavy load of silt that it carries. But now that silt is trapped behind the dam in Lake Powell, and the amount of sediment coming into the river below the dam is a small fration of what it was historically. And that has impacts on a number of resources downstream," she said.
Without that spreading of sediment through the canyon, beaches can't be built up, backwaters used by four species of native, and endangered fish -- the humpback chub, which is the only native species still found within the canyon as the razorback sucker, bonytail chub and Colorado pikeminnow have been extirpated from it -- can't be created, and Native American artifacts can't be covered for preservation and to prevent theft, the assistant secretary said.
The most recent high-flow through Glen Canyon Dam was conducted in March 2008. During that event, the Bureau of Reclamation released water from both the powerplant and the bypass tubes to a maximum amount of approximately 41,000 cubic feet per second for about 60 hours. The results included a robust sandbar building response and sandbar development throughout the river corridor, Interior officials said at the time, adding that considerable erosion occurred following the experiment.
Under the protocol announced Wednesday, the first high-flow release could occur this fall.
“Today’s decisions constitute a milestone in the history of the Colorado River and will provide a scientific foundation to improve future operations to benefit resources in the Grand Canyon, as well as the millions of Americans who rely on the river for water and power," said the Interior secretary.
Secretary Salazar added that the protocol represents the most comprehensive experiment for protection of the Grand Canyon since Interior Secretary Bruce Babbitt authorized the first high-flow release in 1996.