Laserfiche WebLink
<br />002332 <br /> <br />determined in accordance with Article ll(l) ofthe Operating Criteria will utilize a value of not less <br />than 14.85 maf(elevation 3,630 feet) for Lake Powell through the year 2016. <br /> <br />On April 24, 2002, members of the Glen Canyon Adaptive Management Work Group (AMWG) <br />recommended to the Secretary that a 2-year experimental flow test be made from Glen Canyon Dam <br />beginning in water year 2003. The recommendation addressed the decline of two key resources in <br />the Grand Canyon: sediment and population viability of endangered humpback chub. To document <br />the proposed experimental flows, Reclamation, the National Park Service, and the United States <br />Geological Survey jointly prepared the Proposed Experimental Releases from Glen Canyon Dam and <br />Removal of Non- Native Fish EA (September 2002), under NEP A. The EA incorporates a Biological <br />Assessment for the Fish and Wildlife Service under the ESA. A Finding of No Significant hnpact on <br />the experimental releases was signed by the three agencies on December 6, 2002. <br /> <br />Daily high fluctuating releases from Glen Canyon Dam, as part of these experimental flows, were <br />carried out from January through March 2003, and January through March 2004. Releases during <br />these three month periods ranged between a high of20,000 cfs (566 cms) to a low of5,000 cfs (142 <br />cms) each day under revised ramping rates as described in the EA. These high fluctuating releases <br />were intended to benefit the endangered humpback chub by reducing the spawning and recruitment <br />of nonnative fish. <br /> <br />Another aspect of these experimental flows is the retention of sediment in the Grand Canyon To <br />better understand mobilization of sediment and beach and habitat creation in the Grand Canyon <br />corridor, if significant sediment input (over one million metric tons) to the Grand Canyon from the <br />Paria River occurs in the summer or fall of2004, and 800,000 metric tons are retained by January 1, <br />2005, as described in the EA, then a 2-day test release of 40,000 to 44,000 cfs (1,130 cms to 1,250 <br />cms) from Glen Canyon Dam will be made in January 2005. Additionally, a 2-day test release of <br />40,000 to 44,000 cfs (1,130 cms to 1,250 cms) would occur during the period of January through <br />March of2005 if winter sediment inputs exceed 800,000 metric tons as described in the EA, Test <br />releases to mobilize sediment did not occur in 2004 because the required sediment input from the <br />Paria River was not achieved. <br /> <br />On August 11,2004, members ofthe AMWG recommended to the Secretary that replication of the <br />daily high fluctuating releases (5,000 to 20,000 cfs) continue adaptively from January through April, <br />2005. The AMWG also proposed that ifthe Secretary proceeds to implement a high flow release to <br />mobilize sediment in water year 2005, that such release take place in November 2004 rather than <br />January 2005. In making these recommendations, the AMWG expressed a desire to formulate a <br />water year 2005 flow regime from Glen Canyon Dam that is effective at testing the hypotheses of <br />sediment conservation and humpback chub protection in a way that considers the financial condition <br />of the Upper Colorado River Basin Fund. An operation at Glen Canyon Dam may be adopted in <br />water year 2005, pending appropriate environmental compliance to implement the August 11,2004, <br />recommendations ofthe AMWG.(5) Experimental flows will not alter the total volume of water to be <br />released from Lake Powell during water year 2005. <br /> <br />(5) Plots of the monthly release pattern and water surface elevation at Lake Powell under the revised experimental <br />flow proposal are displayed in the attachments to this AOP. <br /> <br />15 <br />