Floodgates opened for river test<br>

Gates are opened at Glen Canyon Dam Sunday in an experiment designed to stir up and redistribute tributary sediment to restore lost beaches and critical habitat for endangered species such as the humpbackchub and Southwestern willow flycatcher.

Under the high-flow test experiment, the Bureau of Reclamation opened the dam’s bypass tubes for 90 hours. The flow peaked in the first 60 hours of the experiment, running at about 41,000 cubic-feet-per-second. The river’s normal flow is between 5,000 and 10,000 cfs.

The test is intended to use flows above power plant capacity to move sediment accumulated in Marble Canyon at the confluence of the Paria and Colorado rivers to rebuild beaches, help improve Colorado River habitat for endangered fish and learn more about the river ecosystem. More than a million tons have accumulated, boosted in part by wet weather this fall, triggering the proposal from the Adaptive Management Work Group, a federal advisory committee that oversees dam management in accordance with the Grand Canyon Protection Act.

The test is being funded through the Adaptive Management Program budget, which is largely funded through hydropower revenues from Glen Canyon Dam. Some additional appropriated funds are included in the budget.

The water released during the experiment is factored into the annual volume set for 2005 Water Year – about 8.23 million feet under the dam’s annual operating plan. That water is sent down river and captured in Lake Mead for use by the Lower Colorado River Basin states. The test flows are factored into that annual volume. Water released above power-plant capacity will not be used to generate power. The National Park Service will extend boat-launch ramps and move docks on Lake Powell and adjust services in Glen Canyon NRA to accomodate the drop in lake elevation.

The high-flow test experiment will advance understanding of the dynamics of the Colorado River ecosystem, with experiments planned to study sediment distribution, native fish and food for aquatic animals. Results will be used to evaluate the use of high flows to redistribute tributary sediment as a management tool for the preservation and restoration of natural and cultural resources in the Colorado River corridor below Glen Canyon Dam.

The experiments are being conducted by the Department of the Interior’s U.S. Geological Survey Grand Canyon Monitoring and Research Center, in collaboration with scientists and resource managers from Interior’s Bureau of Reclamation, Fish and Wildlife Service, National Park Service, Arizona Game and Fish Department, Northern Arizona University and other cooperators.

Research will be supported by pre- and post-release remote sensing to determine how the beaches and sediment in the system respond to the high flows. Aerial photography will be complemented by channel-bed mapping and sediment classification using sophisticated multibeam sonar. Subsequent remote sensing efforts around Memorial Day and 18 months after the test will track changes in the system over time.

USGS scientists will focus their investigations on how much sediment moves through the Grand Canyon during the high-flow event, and how much is retained in the form of beaches or channel deposits.

Shoreline beaches will be measured using a combination of conventional survey equipment and airborne Light Detection and Ranging equipment. LiDAR is a relatively new surveying technology that can deliver highly accurate topography from aircraft flying thousands of feet above the ground in remote locations. Sediment suspended in the water also will be measured using a combination of water sampling and a laser based technology.

For more information regarding the science associated with the experimental high flow, contact Scott Harris, public affairs officer for the U.S. Geological Survey, at 703-648-4054 (office); or 703-785-1113 (cell); or 877-826-5955 (satellite phone). His e-mail is sharris@usgs.gov. The draft EA and Finding of No Significant Impact can be viewed at www.usbr.gov/uc/envprog.amp.


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