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WSP07886
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Last modified
1/26/2010 2:29:19 PM
Creation date
10/12/2006 2:40:00 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8282.600.10
Description
Colorado River Operating Annual Reports
Basin
Colorado Mainstem
Date
1/1/1994
Author
USDOI/BOR
Title
Operation of the Colorado River Basin 1994 Projected Operations 1995
Water Supply Pro - Doc Type
Publication
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<br />Projected Plan <br /> <br />For 1995 operations, three reservoir unregulated inflow <br />scenarios were developed and analyzed 8JId are labeled as <br />probable maximum, most probable, and probable minimum. <br />The National Weather Service Extended Streamflow <br />Prediction (ESP) computer model uses current basin <br />conditions as weU as historical data to predict the range of <br />possible future streamflows. Tbe ESP model was employed <br />to develop each inflow scenario, based on current soil <br />moisture conditions within the basin. Although there is a <br />wide confidence band associated with streamflow fore<:asts <br />made a year in advance, the data are valuable in analyzing <br />the possible impacts on project uses and purposes. A soil <br />moisture deficit developed within the basin due to the dry <br />conditions that were experienced in 1994. This soil moisture <br />deficit is expected to affect the magnitude of inflows in water <br />year 1995. Therefore the magnitude of inflows in each of <br />the three inflow scenarios are less than the historical upper <br />decile, mean, and lower decile (10 percent exceedance, 50 <br />percent exceedance, and 90 percent exceedance, respectively) <br />for each reservoir for water year 1995. <br /> <br />Based on the ESP model results, three different hydrologic <br />scenarios were developed for each reservoir. The volume of <br />inflow resulting from these assumptions was used as input <br />into Reclamation's monthly reservoir simulation model. This <br />model is used to plan reservoir operations for the upcoming <br />24-month period. Projected water year 1995 inflow and 1u1y <br />31, 1994, reservoir storage conditions were used as input to <br />this model and monthly releases were adjusted until release <br />and storage levels accomplished project purposes and <br />priorities. <br /> <br />Minimum instream flow levels have been established at <br />several locations in the Upper Colorado River Basin which <br />are intended to preserve the aquatic resources downstream <br />of specific dams. Tbe regulation of the Colorado River has <br />had both positive and negative effects on aquatic resources. <br /> <br />ControUed cool water releases from dams have provided for <br />increased productivity of some aquatic resources and the <br />development of significant sport fisheries. However, the <br />same releases may be detrimental to endangered and other <br />native species of fishes. <br /> <br />Consultations with the FISh and Wildlife Service in <br />compliance with Section 7 of the Endangered Species Act <br />(Section 7 consultations) on the operation of the AspinaU <br />Unit on the Gunnison River, Navajo Dam on the San 1uan <br />River, and Flaming Gorge on the Green River will continue <br />in 1995. Studies associated with these consultations will be <br />used to beller understand the flow related needs of <br />endangered and other native species of fish. AdditionaUy, <br />interim flow restrictions on releases from Lake PoweU will <br />continue in water year 1995 until a Record of Decision is <br />made on the Glen Canyon Dam Environmental Impact <br />Statement (GCDEIS). <br /> <br />Modifications to planned operations may be made based on <br />changes in forecast conditions. However, due to the <br />Recovery Implementation Programs for Endangered FISh <br />Species in the Upper Colorado River Basin, Section 7 <br />conSultations, and other downstream concerns, modification <br />to the monthly operation plans may not be based solely on <br />changes in streamflow forecasts. Decisions on spring peak <br />releases and downstream habitat target flows may be made <br />midway through the runoff season. Reclamation and the <br />FISh and Wildlife Service will initiate meetings with <br />interested parties, including representatives of the basin <br />States, to facilitate the decisions necessary to finalize site <br />specific operations plans. AU operations will be undertaken <br />subject to the primary water storage and delivery <br />requirements established by "The Law of the River", <br />including Endangered Species Act compliance and other <br />applicable statutes. <br /> <br />There is a reasonable expectation that mainstem <br />consumptive use in the Lower Division States will not exceed <br />9.25 bil1ion cubic meters (75 mil1ion acre-feet) in 1995. It <br />is therefore expected that all reasonable beneficial <br />consumptive use needs of the Lower Colorado mainstem <br />users will be met in calendar year 1995. <br /> <br />4 <br />
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