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WSP11877
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Last modified
1/26/2010 3:19:10 PM
Creation date
10/12/2006 5:15:09 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8220.101.10
Description
Colorado River-Water Projects-Glen Canyon Dam/Lake Powel-Glen Canyon Adaptive Management
Basin
Colorado Mainstem
Water Division
5
Date
9/1/2002
Author
DOI-BOR-NPS-USGS
Title
Proposed Experimental Releases from Glen Canyon Dam and Removal of Non-Native Fish-Environmental Assessment
Water Supply Pro - Doc Type
Report/Study
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<br />" <br /> <br />1> :' <br /> <br />, <br /> <br />To conserve Paria sediment inputs, proposed dam releases will either be reduced to <br />store sediment in the main channel or raised to powerplant capacity to store the <br />sediment in eddies following Paria River inputs. In addition, darn releases up to <br />45,000 cubic feet per second, similar to the 1996 test flow are proposed in an attempt to <br />rebuild beaches, <br /> <br />Non-native trout are known to negatively impact native fish. Daily high fluctuating <br />releases are proposed during January-March to interrupt spawning of adult trout and to <br />displace small trout from their preferred habitats. Proposed mechanical removal of <br />trout by electrofishing will test whether the juvenile and adult trout population can be <br />reduced in a 10-mile reach of Colorado River that contains the largest known number of <br />mainstream humpback chub. About 20,000 rainbow and brown trout are expected to be <br />removed from this river reach in each of two years under the experiment. <br /> <br />The environmental consequences of the Proposed Action are expected to be positive <br />for resources intended to be benefited by the action, though due to the experimental <br />nature of the proposal, there is some uncertainty as to the outcome. The estimated <br />financial cost of the proposed experiment to power customers is about $1.7 million as <br />compared with estimated 2003 power revenues of $130 million under ROD operations. <br />Objectives of this proposed action are in agreement with the 12 management goals of the <br />Glen Canyon Dam Adaptive Management Program and applicable provisions of federal <br />law. <br /> <br />The effects of the various components of the Proposed Action on endangered species <br />have been fully described in Section 3.8, "Endangered Species" (also see Appendix A). <br />With respect to the Proposed Action in total, a condition of "may affect, not likely to <br />adversely affect" is projected for the California condor, razorback sucker (RBS), and <br />Southwestern willow flycatcher (SWWF). A condition of "may affect, likely to adversely <br />affect" is projected for the humpback chub (HBC), Kanab ambersnail (KAS), and bald <br />eagle. It is important to note that the Proposed Action is expected to produce an overall <br />positive benefit to the ecosystem downstream of Glen Canyon Dam, including the <br />endangered species, despite short-term minor impacts to some resources. <br /> <br />The proposed combination of experimental dam releases and non-native fish <br />removal has been developed using knowledge gained in nearly 20 years of research and <br />monitoring of resources in this reach of the Colorado River, first under the Glen Canyon <br />Environmental Studies and now as part of the Adaptive Management Program. <br />Accordingly, this EA provides analysis that builds upon the scientific information <br />developed over this entire period. <br />
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