9605

• UCREFRP Catalog Number: 9605
• Author: Schmidt, J. C. and e. al.
• Title: Flow Recommendations for the White River, Utah-Colorado Draft Report.
• USFW Year: 2002.
• USFW - Doc Type: Logan, UT.
• Copyright Material: NO

discharge measurements indicates that at some time between the measurements the

discharge was sufficient to scour the bed. Mean daily discharges between measurements

where the bed elevation changed more than 0.25 m were determined and compared with

discharges during periods where bed elevation remained constant. We used a two-tailed

t-test and assumed equal variance to determine ifthe maximum discharges during periods

of scour were drawn from statistically different populations than the maximum

discharges when the bed elevation remained constant. We created histograms of the

mean daily discharges for periods of bed stability and periods of scour to facilitate

compansons.

We also used the discharge records to look for long-term changes in channel

width. The distance between right and left edges of water was recorded at the time of

each discharge measurement. This measurement represented the top width of the

inundated portion of the channel at the given discharge, but did not define the boundaries

of the channel. To determine if the width of the channel had changed, we analyzed

discharge measurements made between 10% greater than and 25% less than what we

earlier had determined to be the bankfull discharge of 105 m3/s (3700 ft3/S). Because the

location of discharge measurements varied, we limited the analysis to measurements

made within a 60 m reach extending upstream from the cable.

J

Determination of Dso Particle Sizes

The D5o, or median bed particle size, was determined by performing pebble

counts on representative exposed gravel deposits within the study reach. Six pebble

counts were performed on three exposed or slightly submerged cobble bars during April
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