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Grand Canyon Sandbar Restoration Planned With High Water Flows

LAS VEGAS, Nevada, December 11, 2009 (ENS) – The Department of the Interior will undertake an experimental initiative to improve the management of Glen Canyon Dam and the Colorado River as it flows through Grand Canyon National Park, Secretary of the Interior Ken Salazar announced Thursday during the Colorado River Water Users Association conference.

“We must find a way to protect one of the world’s most treasured landscapes, the Grand Canyon, while meeting water and clean energy needs in the face of climate change,” Salazar said in a video message to the water users’ meeting at Caesar’s Palace in Las Vegas. The video was taped in Copenhagen where Secretary Salazar is participating in the global climate change conference.

“Today, I am directing the development of a protocol for conducting additional high flow experiments at the dam,” Salazar said.

“These experimental high flows, like the one in 2008, send sediment downstream to rebuild sandbars, beaches and backwaters. The rebuilt areas provide key wildlife habitat, enhance the aquatic food base, protect archeological sites, and create additional camping opportunities in the canyon,” he said.

Rafters on the Colorado River enjoy a sandbar in the Grand Canyon. (Photo courtesy USGS)

Because Glen Canyon Dam traps about 90 percent of the sand once available to maintain Grand Canyon sandbars, high flows are a good tool to rebuild these resources.

The new protocol will allow for high flows to occur when Colorado River tributaries below the dam produce sufficient sediment to meet a threshold, or trigger.

Timing of high flows would depend not only on sediment inputs from tributaries, but also other environmental considerations such as impacts to the Lees Ferry trout fishery and riparian vegetation.

The new protocol will protect the interests of those relying on the Colorado River, Interior officials said, because the water released during the high flow will not change the annual amount of water to be released to downstream users from Glen Canyon Dam.

That water flows downriver to Lake Mead for use by the Lower Colorado River Basin States and Mexico.

“We’ve put in place a comprehensive science program designed to figure out the complex processes at work downstream of Glen Canyon Dam, so that we can get better at managing the river for the benefit of all the various resources at stake,” Assistant Secretary Anne Castle explained in a follow-up speech to the Las Vegas audience.

“We can make high flow releases of short duration without affecting the overall amounts of water required to be released from Lake Powell by the 2007 interim guidelines and the Law of the River,” Castle said.

“We will engage all our partners in this effort – from federal agencies and tribes to local and state governments and other stakeholders,” Salazar said.

“We also recognize the need for additional experimental and management actions to protect the resources of Grand Canyon National Park, and these efforts will be implemented through the Glen Canyon Dam Adaptive Management Program,” the secretary said.

The most recent high flow experiment at Glen Canyon Dam was conducted in March 2008. During the experiment, the Bureau of Reclamation released water from both the power plant and the bypass tubes to a maximum amount of approximately 41,000 cubic feet per second for about 60 hours.

Preliminary results of the 2008 experiment show a robust sandbar building response and sandbar development throughout the river corridor. However, considerable erosion occurred following the experiment.

Research on the effects of the 2008 event on a range of resources, including native fish, vegetation, and the Lees Ferry trout fishery, will be completed by the U.S. Geological Survey in January 2010 and this additional information will be taken into consideration in the development of the new high flow protocol.

Grand Canyon National Park lies 15 miles down-river from Glen Canyon Dam, which was built on the Colorado River just south of the Arizona-Utah border in Glen Canyon National Recreation Area. Before the dam began to regulate the Colorado River in 1963, the river carried such large quantities of red sediment that the Spanish named the river the Rio Colorado, or “red river.”

Today, the Colorado River usually runs clear below Glen Canyon Dam because the dam nearly eliminates the main-channel sand supply. The daily and seasonal flows of the river were also altered by the dam. These changes have disrupted the sedimentary processes that create and maintain Grand Canyon sandbars.

Throughout Grand Canyon, sandbars create habitat for native plants and animals, supply camping beaches for river runners and hikers, and provide sediment needed to protect archaeological resources from weathering and erosion.

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