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Last modified
1/26/2010 4:34:15 PM
Creation date
3/25/2008 3:17:42 PM
Metadata
Fields
Template:
Water Supply Protection
File Number
8282.600.40
Description
Colorado River AOP Status Report
Basin
Colorado Mainstem
Author
USDOI/BOR
Title
Colorado River Reservoir Operations Status Reports Partial Part 2 2004, with staff comments
Water Supply Pro - Doc Type
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<br />Assessment. "Experiments such as this high-flow test continue to advance our understanding of the <br />ecosystem while providing tangible benefits to the fishery, river environment, and recreational users <br />in Grand Canyon National Park." <br /> <br />In August 2004, members of the Glen Canyon Adaptive Management Work Group recommended to <br />Secretary Norton that high-flow tests be considered for later in the year if sufficient accumulations <br />of sediment were present in the Colorado River near the confluence of the Paria River. <br /> <br />In October, the Grand Canyon area experienced significant rainstorms that produced Paria River <br />sediment inputs sufficient to trigger such a test. The primary purposes for conducting the high-flow <br />tests are to restore sandbar deposits in the upper reaches of the Grand Canyon and recreate numerous <br />backwater channels that serve as prime spawning areas and habitat for the humpback chub and other <br />native fish species. <br /> <br />The Draft Supplemental Environmental Assessment is available for public review on the Internet by <br />following the link at www.usbr.gov/uc/envdocs/eaJgc/SuppEA-ltr.pdf <br /> <br />The high-flow test would not alter the total volume of water released from Lake Powell in water year <br />2005. <br /> <br />Upper Colorado River Basin Hydrology <br /> <br />Water year 2005 began on October 1, 2004. The Colorado River Basin has now completed 5 <br />consecutive years of drought. In the summer of 1999 Lake Powell was essentially full, with <br />reservoir storage at 97 percent of capacity. Since that time, inflow volumes have been below <br />average for 5 consecutive years. The last month when inflow to Lake Powell was above average <br />was September 1999. Total unregulated inflow to Lake Powell in water year 2004 was only 51 <br />percent of average. Unregulated inflow in water years 2000, 2001, 2002, and 2003 was 62, 59, 25, <br />and 51 percent of average, respectively. Inflow in water year 2002 was the lowest ever observed <br />since the completion of Glen Canyon Dam in 1963. <br /> <br />A favorable trend has emerged the past two months in the Colorado River Basin. Precipitation in <br />September and October was above average in the basin. Basin wide precipitation in September was <br />165 percent of average, with October precipitation at 155 percent of average. In October, the highest <br />proportion of the precipitation occurred in Utah, with many areas in Utah receiving over 200 percent <br />of average precipitation. October precipitation in western Colorado was near average. <br /> <br />Inflow to Lake Powell, which was extremely low this past summer (only 35 and 29 percent of <br />average in July and August, respectively), has picked up in response to the storms of the past two <br />months. Unregulated inflow to Lake Powell in September was 68 percent of average and 92 percent <br />of average in October. As of November 7, 2004, observed inflow to Lake Powell was 8,000 cfs, 78 <br />percent of what is normally seen in early November. The reality, however, is that we are still very <br />early in water year 2005, and drought conditions continue to prevail in the Colorado River Basin. <br />To "break" the drought will require the pattern of above-average precipitation to continue through <br />the winter and into next spring. Water year 2005 is off to a good start, but it is still too early to <br />celebrate. <br /> <br />Low inflows over the past 5 years have reduced water storage in Lake Powell. As of November 8, <br />2004, the current elevation of Lake Powell is 3,570.5 feet (129.5 feet from full pool). Current <br />storage is 9.2 million acre-feet (38 percent of live capacity). <br /> <br />Under the current inflow forecast, the water surface elevation of Lake Powell is projected to decline <br />the remainder of the year, with current projections showing the lake reaching an elevation of about <br />
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