Downstream Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem (1999) / Chapter Skim
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Appendix D: Record of Decision (1996)
Appendix D: Record of Decision (1996)
Pages 167-188
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From page 167... ...
Appendix D Record of Decision (1996)
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From page 169... ...
on the Operation of Glen Canyon Dam Final Environmental Impact Statement (EIS) We are pleased to provide you with the enclosed copy of the subject ROD which was signed by the Secretary of the interior on October 9, 1996.
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From page 170... ...
170 Approved RECO~ OF DECISION OPERATION OF GLEN CANYON DAM Final Environmental Impact Statement October 1996 =: 5~ Den. Qcr ~ 8 tg96 Appendix D I= 09 19N ,- 6' ~
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From page 171... ...
of the Act requires the Secretary to operate Glen Canyon Dam: "...in such a manner as to protect, mitigate adverse impacts to, and improve the values for which Grand Canyon National Park and Glen Canyon National Recreation Area were established, including, but not limited to natural and cultural resources and visitor use. " Alternatives considered include the No Action Alternative as well as eight operational alternatives that provide various degrees of protection for downstream resources and hydropower production.
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From page 172... ...
and will provide high steady releases of short duration, which will protect or enhance downstream resources while allowing limited flexibility for power operations. The Modified Low Fluctuating Flow Alternative incorporates beach/habitat-building flows which are scheduled high releases of short duration designed to rebuild high elevation sandbars, deposit nutrients, restore backwater channels, and provide some of the dynamics of a natural system.
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From page 173... ...
The 4,000 cubic feet per second per hour upramp rate limit will be implemented with the understanding that results from the monitoring program will be carefully considered. if impacts differing from those described in the final EIS are identified, a new ramp rate criterion will be considered by the Adaptive Management Work Group and a recommendation for action forwarded to the Secretary.
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From page 174... ...
Interim Low: Substantially reduce daily fluctuations from historic levels; same as interim operations except for addition of common elements. STEADY FLOWS Existing Monthly Volume: Provide steady flows that use historic monthly release strategies.
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From page 175... ...
Comments regarding interests and values were categorized as: expressions about the Grand Canyon, economics, nonquantifiable values, nature versus human use, and the complexity of Glen Canyon Dam issues. The ElS team consolidated and refined the public issues of concern, identifying the significant resources and associated issues to be analyzed in detail.
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From page 176... ...
176 Appendix D .m ;^ cat a, o au .~ cd o .~ .s o En ~ T; ~to E ~0 5 W o a c Hi ° x 2.
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From page 177... ...
Appenclix D 177 O ~-X3 ~ O c)
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From page 178... ...
Glen Canyon Environmental Studies Phase II identified cause and effect relationships between downramp rates and adverse impacts to canyon resources. However, no cause and eject relationships between upramp rates and adverse impacts to canyon resources were identified.
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From page 179... ...
COMMENT: Do not change the upramp rate and maximum flow criteria at the same time. While acknowledging RecIamation's good efforts to identify and establish optimum operating criteria for all users of Glen Canyon Dam, changing two flow criteria (upramp rate and maximum flow criterion of preferred alternative)
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From page 180... ...
COMMENT: Endorse the Fish & Wildlife Service's Biological Opinion and implement experimental steady flows to benefit native fishes, subject to the results of a risk/benefit analysis now in progress. RESPONSE: The preferred alternative provides for experimental steady flows through the Adaptive Management Program for the reasons put forth in the Biological Opinion.
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From page 181... ...
RESPONSE: While the preferred alternative may not satisfy all interests, Reclamation believes it is a workable compromise and meets the two criteria set out in the ElS for the reoperation of the dam, namely restoring downstream resources and maintaining hydropower capability and flexibility. A letter of comment from the Environmental Protection Agency (EPA)
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From page 182... ...
2. Monitoring and Protection of Cultural Resources: Cultural sites in Glen and Grand Canyons include prehistoric and historic sites and Native American traditional use and sacred sites.
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From page 183... ...
Based on the impact analysis described in the final EIS, three of the alternatives are considered to be environmentally preferable. They are: the Moderate Fluctuating Flow Alternative, the Modified Low Fluctuating
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From page 184... ...
to the Year-Round Steady Flow Alternative that would have eliminated all river fluctuations and peaking power capabilities. Within this range, the Maximum Powerplant Capacity, No Action, and High Fluctuating Flow alternatives were eliminated from consideration as the preferred alternative because they would not meet the first criterion of resource recovery and long-term sustainability.
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From page 185... ...
The selected Modified Low Fluctuating Flow Alternative is an improved version of the Interim Low Fluctuating Flow Alternative because it would provide for some pre-dam variability through habitat maintenance flows. The three remaining alternatives-the Moderate Fluctuating, Modified Low Fluctuating, and Seasonally Adjusted Steady Flow Alternatives- provide similar benefits to most downstream resources (e.g..
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From page 186... ...
Although the Moderate Fluctuating, Modified Low Fluctuating, and Seasonally Adjusted Steady Flow Alternatives provide similar benefits to most downstream resources, the Modified Low Fluctuating Flow Alternative was selected as the preferred alternative because it would provide the most benefits with respect to the original selection criteria, given existing information. This alternative would create conditions that promote the protection and improvement of downstream resources while maintaining some flexibility in hydropower production.
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From page 187... ...
The influence of variable discharge regimes on Colorado River sand bars below Glen Canyon Dam. Glen Canyon Environmental Studies, Report PHYOlOl, Chapters I through 7 Northern Arizona University, Flagstaff, Ariz.
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From page 188... ...
Glen Canyon Environmental Studies, Report Pen' 0101, Chapter 4 k The influence of variable discharge regimes on Colorado River sandbars below Glen Canyon Dam, Report PHY O 101. National Park Service, Ft.
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