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Last modified
1/26/2010 4:17:09 PM
Creation date
8/6/2007 1:47:16 PM
Metadata
Fields
Template:
Water Supply Protection
File Number
8220.101.10.B
Description
Colorado River - Water Projects - Glen Canyon Dam-Lake Powell - Glen Canyon TWG
State
CO
Basin
Colorado Mainstem
Water Division
5
Date
10/1/2004
Author
Schmidt - Topping - Grams - Hazel
Title
System-Wide Changes in the Distribution of Fine Sediment in the Colorado River Corridor Between Glen Canyon Dam and Bright Angel Creek - Arizona - Final Report - 10-01-04
Water Supply Pro - Doc Type
Report/Study
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<br />002341 <br /> <br />sucker (Xyrauchen texanus). Riparian vegeta- <br />tion occurs in two distinct zones: one relict of <br />the pre-dam hydrologic conditions and a <br />denser assemblage at lower elevation that is an <br />artifact of the post-dam flow regime. Both <br />vegetation zones constitute habitat for birds <br />and other fauna. <br />The stream flow that maintains this <br />riverine ecosystem and is the focus of so many <br />people's recreational experience is determined <br />by water releases from Glen Canyon Darn. <br />Today's floods are much smaller and today's <br />base flows are much larger than those which <br />occurred prior to the dam. The existence of the <br />dam also blocks all sediment delivered from <br />the Colorado River upstream from Lake <br />Powell reservoir. When the reservoir is full, <br />stream flow temperature averages 80C. <br />These changes to water flow, sediment <br />transport, and water temperature have trans- <br />formed the geomorphology and ecology of the <br />Colorado River and its alluvial valley <br />(Carothers and Brown, 1991; National Re- <br />search Council, 1991; U.S. Department of the <br />Interior, 1995; Webb, 1996). Among the <br />geornorphic features affected by the dam's <br />existence and operations are fme-sediment <br />deposits, the size and abundance of which are <br />indicators of the degree to which the post-dam <br />ecosystem has been altered from the pre-darn <br />condition (National Research Council, 1996). <br />The purpose ofthis paper is to describe <br />the physical transformation of the channel and <br />alluvial deposits of the Colorado River during <br />the twentieth century in Glen, Marble, and <br />upper Grand Canyons, with emphasis on fine <br />sediment (Fig. 1). The upstream end ofthe <br />study area is Glen Canyon Darn, located at <br />River Mile -151. The downstream end of the <br />study area is River Mile 87, which is the <br />location ofU. S. Geological Survey (USGS) <br />gaging station 09402500 (Colorado River near <br /> <br />1 Locations in the study area are described in terms of <br />the distance, in river miles, from Lees Ferry. Distance <br />downstream is positive, and distance upstream is <br />negative. Locations are cited to the nearest 0.1 mile, <br />based on the location system of the Grand Canyon <br />Monitoring and Research Center (GCMRC). <br /> <br /> <br /> <br />..111t\'v <br /> <br />._ l ... <br />." :"~.'. i . <br />. . -'.', ~-:l <br /> <br />':. - <br />'11t'W <br /> <br />Figure 1. Map showing the 4 river segments (in capital <br />letters) that comprise the study area. Five study <br />reaches where historical aerial photographs were <br />analyzed are shown in boxes: (1) Lees Ferry Reach, (2) <br />Redwall Gorge Reach, (3) Point Hansborough Reach, <br />(4) Tapeats Gorge Reach, and (5) Big Bend Reach. <br />The sixth study reach was all of Glen Canyon. NAU <br />study sites are indicated by *,with location in River Mile. <br /> <br />2 System-wide Changes in the Distribution of Fine Sediment in the Colorado River Corridor ... <br />
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