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STUDY AREA <br />The study area encompassed the 17.7 mile stretch of the Colorado river from the Bureau of Land <br />Management boat launch at RM 127.7 to the Cisco Takeout at RM 110 (Figure 1). Westwater <br />Cam-on (RM 124.5 - 114.5) represents a geologic anomaly of upthrust Precambrian material. The <br />exposed metamorphic gneiss is harder than the overlying sandstones resulting in a deep (maximum <br />depth of 21.8m recorded at RM 124.1), confined channel. The habitat in the upper portion of the <br />canyon consists of runs, eddies, and pools interspersed between riffles and rapids. Average <br />gradient through Westwater Canyon in 11.8 ft/ mile; for comparison, gradient through Desolation <br />Canyon averages 6.2 ftlmi. The steepest part of Westwater Canyon, RM 119 - 116.5, was not <br />sampled due to the turbulent flows and Class III rapids. This stretch likely supports native chubs. <br />The lower portion of Westwater Canyon, RM 116.5 -114.5, was a confined canyon reach, but <br />gradient drops and habitat consists primarily of a homogeneous run and chubs are scarse. The <br />canyon is bracketed both upstream and downstream by broad alluvial areas with complex channels <br />flowing over cobble substrates. <br />For the period of record (1951 through present) at the State Line USGS gage (09163500) mean <br />daily flows have ranged from 960 cubic feet per second (cfs) in 1956 to 68,300 cfs in 1984. <br />Throughout the period of study flows ranged from a low of 2020 cfs recorded in late July, 1994 <br />to a instantaneous peak of 49,300 cfs recorded June 19, 1995 (Figure 2). <br />DRAFT <br />3 <br />