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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 />01201 <br /> <br /> <br />CHAPTER 3.0 <br />Affected Environment and <br />Environmental Consequences <br /> <br />This chapter describes resources that are linked to dam operations and the expected or <br />predicted effects of the Proposed Action and No Action alternatives on them. Conditions that <br />currently exist under ROD or No Action dam operations establish the baseline for the <br />description of the affected environment and resources. The affected resources include water, <br />sediment, fish and wildlife, vegetation, endangered and other special status species, cultural <br />resources, recreation, hydropower, and air quality. The indicators used for analyzing impacts <br />on these resources are the same as those used in the FEIS (Reclamation 1995a). <br /> <br />Because of the experimental nature of the Proposed Action, in some cases there is <br />uncertainty in the precise magnitude or direction of effects. Estimates of adverse and <br />beneficial effects presented in this environmental assessment and biological assessment' are <br />based on the best information currently available to the lead agencies. While there may be <br />some short-term impacts to some resources, the Proposed Action is expected to result in a <br />long-term benefit to the ecosystem. It is important to reiterate that the Proposed Action was <br />designed to reverse trends in two key resources, humpback chub and sediment conservation. <br />Both these resources have experienced significant and unexpected declines since adoption of <br />ROD operations in 1996. <br /> <br />3.1 COLORADO RIVER ECOSYSTEM LINKAGES <br /> <br />Resources downstream from Glen Canyon Dam through Glen and Grand canyons are <br />interrelated or linked because most of them are associated with or dependent on water and <br />sediment (Reclamation 1995a). The proposed experimental flows would alter hydrology and <br />sediment transport patterns from ROD operations. Changes in these two processes would, in <br />turn, affect other resources, and the effects will vary in both intensity and duration. In general, <br />if there are no additional disturbances, and Glen Canyon Darn operations return to ROD <br />operations after the Proposed Action, resources would likely return to their No Action <br />conditions after varying time spans. <br /> <br />Today, the ecological resources of Glen, Marble and Grand canyons depend on the water <br />releases from the darn and variable sediment input from tributaries. A reduced sediment <br />supply and regulated release of reservoir water now support aquatic and terrestrial systems <br />that did not exist before Glen Canyon Dam. Table 3.1 summarizes the expected impacts from <br />the No Action and Proposed Action Alternatives. <br /> <br />3 Appendix A contains the biological assessment for the Proposed Action. <br />
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