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Last modified
1/26/2010 3:16:33 PM
Creation date
10/12/2006 4:48:50 AM
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
1/1/2002
Author
Webb-Melis-Valdez
Title
Observation of Environmental Change in Grand Canyon Arizona
Water Supply Pro - Doc Type
Report/Study
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<br />,,'i.;~t;%t <br />j~. - <br /> <br />,.e.!, <br />.rt <br /> <br />Table 2. Dates and observations of the Colorado River being trozen at Lee's Ferry. Arizona, or other points along the river. <br /> <br />Date Observations <br /> <br />January 186h RIver fWl.l'n at Crus!.'ing nt the Fathers In Glen Canyon. allowing Navlljo Iraders (0 cross 0I1lhe ke (Wt'hh, 1996. p. 97). <br />.l:Jnuar)' 15. lX7b I{JVel lroLl'n fl)r IwO wech. ~\'Iormon ml~~ltlrl;Jrit:., l:ltlw::d ulllhe ice pulling \~agons acrl)~~ (Webb. 1996. p 97 and n(ll~' 54; Reilly, <br />1999. p 75). <br /> <br />December JI, 1879 Ri\'er frozen for t'ne day, lung enou~h lor MOftnnlll'olunlSls to move animals and WJgOll." ,H:r~l<'~ the ri\"t"r (.Webb. 1996. p. 97). <br />January 11, 189~ River fruzen. R.B. Stanton wwed downstream (lnd had lochtlp Ihrough Ihe Kt' to reach Lt'e'~ Ferry (Reilly. 1999, p. 154-160t <br />]ate Decemher. 189S Animnls were crusst"d over the river on the ice (Reilly. ]999. p. 1701. <br />laic December. 1911 Men t"To~~ed Ihe river. frozen for several day.... on foot (Reil]y. ] YlJlJ. p. 2451. <br />J:Jnuary I -2. 1925 N;JVll.lO Irader~ druVt" pack mules acro~s the river (Webb. 1996. p. 97). The mer was frozen for ne;Jrly (I month (Reilly. I l}l}y, p. <br />170). <br /> <br />] 92R COl11plelion of Navajo Bndgt" elirninalcs ob~e"'ation~ of Ihc ri\'t"r freezmg l'.'l;ct"pt in gaglllg ~tation recQrds (Webb. 1996. p. 225). <br />1933 Ice lltTected the gaging record a\ Lee'!.' Ferry forM days. from December ]CJ_~2 to Febmary IY:l3. <br /> <br />choppier and seemed to have extra force when hitting <br />the boats and passengers. Many historical river trips <br />experienced sandstorms. which are uncommon now. <br />On his trips in 1937 and 1938, Buzz Holmstrom noted <br />several of these. commenting that "windy all night - <br />sand in everything this morning" (1937) and "sky so <br />full of sand sun blotted oUl" (1938). Erosion of <br />sandbars. as well as the increased size of sand in the <br />ones that remain, minimize the potential for significant <br />sandstorms alung the river corridor at present. <br />Nevills Slaveley was impressed with the high <br />degree of cooperation among guides now, instead of <br />the competitive atmosphere that prevailed on her last <br />trip. Rigg and Nevills Stave ley remarked that the <br />deterioration of air quality as a major change; Rigg <br />stated that the sky was much hazier now than when he <br />ran the river and that it significantly degraded the <br />experience. He also lamented the loss of the Bass <br />cableway, which once spanned the river downstream of <br />Bass Rapid (mile 1(8). <br /> <br />Water Temperature <br /> <br />The cold water released from the bottom of Lake <br />Powell was a very noticeable change to most of the Old <br />Timers, who generally experienced the warm water of <br />summer on their river trips. Generally, the water <br />temperature of releases at the dam are about 490F year <br />round. meaning that the river is cold in summer and <br />warn, in winter. Historical observations of the river <br />freezing over in winter (Table 2), are important to <br />understanding changes in aquatic habitat as a result of <br />the presence of Glen Canyon Dam as well as <br /> <br />potentially understanding the effects of climate on the <br />river. As discussed in Webb (1996). the river froze <br />frequently in the late 19th century. occasionally with <br />enough ice to allow the passage of wagons over its <br />surface at Lee's Ferry (Table 2). <br /> <br />Geomorphology <br /> <br />The Colorado River in Grand Canyon has <br />numerous debris fans, debris bars, and eddies that <br />infiuence its longitudinal profile. The debris fans <br />generally occur at the mouths of Iributarie.s and create <br />constrictions and rapids. Cobbles and boulders are <br />reworked from the debris fan and transported <br />downstream: these particles accumulate in debris bars <br />that create secondary constrictions and rapids. The <br />primary and secondary rapids are separated by a pool <br />that typically has an eddy on one or both channel <br />margins. Eddies form between the debris fan and debris <br />bar or other downstream obstructions. such as bedrock <br />walls. Sand bars are deposited on both the upstream <br />and downstream sides of the debris fan, as well as on <br />the downstream side of the eddy (Schmidt and Graf, <br />1(90). All of these geomorphic features have changed <br />historically (Webb, 1996), and were mentioned by the <br />Old Timers. <br /> <br />Debris Flows and Floods <br /> <br />Two types of tributary fioods occur in Grand <br />Canyon (Melis, 1997: Melis and others, 1994). Debris <br />fiows are slurries of water and poorly sorted sediment <br />that transport large boulders into the Colorado River, <br />creating rapids. The sediment concentration of debris <br /> <br />B OBSERVArlONS OF ENVIRONMENTAL CHANGE IN GRAND CANYON <br />
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