Reclamation To Initiate Experimental Releases from Dam to Evaluate Effects on Sediment Conservation, Native Fish Habitats

The Bureau of Reclamation, in conjunction with the National Park Service and the U.S. Geological Survey, will soon begin a series of alternating steady and low fluctuating experimental releases from Glen Canyon Dam to evaluate fine sediment conservation measures and effects on native fish near shore rearing habitats in the Colorado River downstream of the dam.

Over the course of Sept. 1 to Sept. 3, Reclamation will reduce releases from Glen Canyon Dam. In August, releases have been fluctuating between a low of 10,000 cubic-feet-second (cfs) to a high of about 18,000 cfs each day. By Sept. 3, the daily release pattern will be reduced to a range of 6,500 to 9,000 cfs. These lowered daily fluctuations will continue until Sept. 21 at which time releases will change to a steady release of 8,000 cfs. On Oct. 8, dam releases will revert back to 6,500 to 9,000 cfs daily fluctuations. These fluctuations will be replaced on Oct. 20 with a resumption of steady 8,000 cfs, which will persist through the remainder of October. Normal dam operations will resume on Nov. 1.

In November 2004, as a precursor to this year's experimental releases, Reclamation and various other federal and state agencies conducted a scientific study on the use of high flows from Glen Canyon Dam to conserve sediment that had accumulated below the confluence of the Paria River in Marble Canyon. The high flows were released from the dam following input of approximately one million metric tons of fine sediments to the Colorado from the Paria and other tributaries.

The purpose of the high flow was to determine the extent to which it is possible to rebuild beaches and backwater habitats as a means to improve natural resources in the Grand Canyon. Under the high flow test experiment, the peak flow released from Glen Canyon Dam reached approximately 41,000 cfs and lasted for two and one-half days (60 hours). The water released from Glen Canyon Dam during the experiment did not change the amount of water to be released over the course of the 2005 water year.

Both the high flow test conducted in November 2004 and the upcoming experimental releases are being implemented based on recommendations made by the Adaptive Management Work Group of the Glen Canyon Dam Adaptive Management Program (GCDAMP), a federal advisory committee to the Secretary of the Interior, in August 2004. These actions are being implemented in water years 2005 and 2006 to improve the potential for success in achieving the purposes of the original action agreed to in 2002.

The Adaptive Management Work Group is a federally chartered advisory group to Secretary of the Interior Gale Norton that meets on a regular basis to review the impacts of Glen Canyon Dam on downstream resources and to develop recommendations on management actions to protect the downstream ecosystem. The Adaptive Management Program provides a process to implement both the Grand Canyon Protection Act of 1992 and the 1996 Record of Decision for the Operation of Glen Canyon Dam Environmental Impact Statement. Additional information concerning the Adaptive Management Program and the work of the Adaptive Management Work Group may be found on the Bureau of Reclamation's Web page at http://www.usbr.gov/uc/rm/amp/index.html.

This article originally appeared in the 08/01/2005 issue of Environmental Protection.

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