7848

• UCREFRP Catalog Number: 7848
• Author: Burdick, B. D.
• Title: Minimum Flow Recommendation For Passage Of Colorado Squawfish And Razorback Sucker In The 2.3-Mile Reach Of The Lower Gunnison River
• USFW Year: 1997.
• USFW - Doc Type: Redlands Diversion Dam To The Colorado River Confluence.
• Copyright Material: NO

three months. In 1995, there were only four days when the flow was less than
1,000 cfs in the reach during these three summer months--the lowest flow being
650 cfs on 6 September.
The actual streamflows calculated by subtracting the flow of the Redlands
Canal from the USGS gage at Whitewater were always higher than the streamflow
measured by the BR gage in the reach. During low flows, the instantaneous flow
varied from 150-200 cfs in the 2.3-mile reach. The exact reason for this
discrepancy was unknown. The Whitewater gage is located about 11 miles upstream.
The difference between the two methods might be explained during runoff by the
rapid hourly flow fluctuations and by the difficulty in determining the flow rate
and "flow lag time" between the dam and upstream gage. However, the discrepancy
is not explained during low-flow periods when the hourly and daily fluctuations
are not great. The mean daily flow in the 2.3-mile reach for the two methods
during study period is provided (Appendix F; Figure F.1.).
BR Transects (Figure 6; Appendix; Tables G.1-G.3)
Transect No. 1 (Appendix; Figure G.1.)
This transect was located at RM 3.0, the plunge pool of the Redlands
Diversion Dam. The plunge pool offers deep-water habitat for Colorado squawfish
when flow totally ceases in the reach. At 100 cfs, the mean and maximum water
depth is 6.7 and 9.7 feet, respectively. At 300 cfs, the mean and maximum water
depth is 7.6 and 10.4 feet, respectively (Appendix; Table G.U. In the 2.3-mile
reach, Colorado squawfi sh and other native fishes have two options in coping with
low-flow conditions. One is to travel downstream to the Colorado River and wait
out the low-flow period in reaches below the confluence with the Colorado River
where more water is available. The other strategy is to 'hole up' in habitats
that provide adequate deep-water habitats, such as the plunge pool. Although the
deep-water habitat of the plunge pool has been artificially created by the
Redlands Diversion Dam, it does provide a temporary sanctuary for fish that might
become stranded during low-flow periods.
Transect No. 2 (Appendix; Figure G.1.)
This transect was located at RM 3.0, immediately downstream of Transect 1.
Two prominent thalwegs, one on river right and the other on river left, and a
mid-channel sandbar appear in this transect profile. At 100 cfs, the mean and
maximum water depth is 3.0 and 5.9 feet, respectively. The right thalweg,
deepest of the two channels, is maintained by the flows released when the radial
arm gates on river left are opened to sluice sediments from upstream of the dam.
This area also provides deep-water habitat for Colorado squawfish during extreme
low-flow conditions (e.g., 100 cfs or less). There is not an appreciable gain
in habitat if flow is increased from 100 cfs to 300 cfs or from 300 to 600 cfs
at this transect.
Transect No. 3 (Appendix; Figure G.2.)
This transect was located at RM 2.85 and was the widest of all transects
(549 feet). Because of the wide nature of this section of the river, an increase
20