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Last modified
1/26/2010 12:29:52 PM
Creation date
10/11/2006 10:15:58 PM
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
11/5/2004
Author
DOI-BOR-NPS-GCMRC
Title
Draft Supplemental Environmental Assessment-Proposed Experimental Actions for Water Years 2005-2006
Water Supply Pro - Doc Type
Report/Study
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<br />Proposed Water Year 2005-2006 Experimental Actions <br /> <br />01817 <br /> <br />9 <br /> <br />flows during September and October will not exceed daily fluctuations of 5,000-10,000 <br />cfs, Small fluctuations may provide more food resources in the varial zone between the <br />high water and low water stage, but the difference is not expected to be significant to the <br />ecology of these animals, <br /> <br />High Experimental Flow <br /> <br />Differences between the No Action and Proposed Action are expected not be measurable <br />for reptiles and amphibians, In 2003, the Hopi Tribe raised concerns about the <br />potentially negative effects of high flows on hibernating frogs, lizards, and snakes, <br />Although data are apparently not available to provide direct evidence of this fonn of <br />mortality in the Grand Canyon ecosystem, the potential exists to flood hibernacula of <br />reptiles and amphibians during colder times of the year, Hypothetically, such mortality <br />should be low since natural selection would strongly influence reptiles and amphibians <br />to locate their hibernacula above sites that are routinely subject to flooding and <br />inundation, Descriptive field observations in support of this hypothesis were presented <br />in a final report from the Hopi Tribe (Huisinga and Yeatts (2003), They reported only <br />four Grand Canyon rattlesnakes observed during the winter months of February-March, <br />and aU four were located in talus slopes or upland mesquite/boulder habitats. We <br />anticipate that these conditions also would exist in the timeframe of high experimental <br />flows under either the No Action or Proposed Action, <br /> <br />Non-native Fish Suppression Flows <br /> <br />These flows largely occur at a time of year when reptiles are inactive, April is a period of <br />increased activity for reptiles, but their activity is still dependent on ambient <br />temperatures and food availability. Following a high experimental flow, which can <br />occur under either the No Action or Proposed Action, there will be increased open areas <br />for reptile foraging, Differences in effects on amphibians between the two alternatives <br />are expected not to be measurable. <br /> <br />Trout <br /> <br />Alternating Low Steady and Low Fluctuating Flows <br /> <br />These autumn flows are expected to cause minor decreases in the amount of drift <br />available for trout food during the period of steady flows, but the duration of these <br />flows is brief and the effects are expected to be short-lived, <br /> <br />High Experimental Flow <br /> <br />The high experimental flow of approximately 41,000 cfs is expected to affect trout <br />through shorHenn changes in displacement of individuals and increased mortality, <br />
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