WSP01905

• File Number: 8240.200.40.J
• Description: Yampa
• State: CO
• Basin: Yampa/White
• Water Division: 6
• Date: 1/6/1993
• Title: City of Craig, Colorado River, Yamoa River Diversion Fish Passage Study
• Water Supply Pro - Doc Type: Publication

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Electrofishing catch rates in the 0.1 miles below the diversion structure were generally lower
than other areas within the study area. Catch rates calculated for all species combined for the
electroflShing runs conducted exclusively in the plunge pool were 448.3 fish/l0 hours, This compared
to a catch rate of 1102.4 fish/l0 hours for all other electrofishing runs conducted during the study.
Increases in catch rates in the plunge pool below the structure from 187.5 flSh/l0 hours during Trip
4 and 204 fish/l0 hours during Trip 2 to 836.7 fish/l0 hours during Trip 4 suggest the possibility of
increased numbers of fish below the structure during low flows in September. Increased densities may
be related to a tendency for fISh to collect in deeper habitats, like those associated with the diversion
structure during low, clear flows.

Physical Habitat Assessment

Flows. Flows encountered during the study ranged from ahigh of2,180 cfs on June 8 to a low
of 155 cfs on October 23 (Table 12). Highest daily average flow for 1992 was 4,700 cfs on May 28
with an instantaneous peak of 5,020 cfs occurring on May 27 (USGS, Meeker, Colorado - provisional
data). This flow occurred between Trip 1 and Trip 2 of the study, The lowest daily mean flow of
134 cfs occurred on September 2, between Trips 3 and 4.

Late summer base flows in the study area were artificially augmented by the drawdown of two
reservoirs in the upper Yampa River drainage, including Steamboat Lake and Fish Creek Reservoir.
These drawdowns were conducted for several weeks in September and completed by September 25.
Reduction in flow during Trip 4 from 437 to 161 cfs was associated with the completion of the
reservoir drawdowns.

Phvsical Habitat Measurements. Physical habitat measurements including depth and velocity
were taken in the fish passage notch, chute and plunge pool during Trips 4 and 5. Figure 2 is a
representation of the middle section of the diversion structure including the low flow fish passage
notch and chute. A majority of the discharge passes through these features of the structure at low
flows and they represent the probable pathway for a passing fish. The plunge pool (not depicted in
Figure 2) is located immediately below the third stationary V-shaped wave. Measurements taken
during Trip 4 were primarily directed at locating maximum depths and velocities. Flows during the
period when measurements were taken were approximately 164 cfs. Depths in the fish passage notch
and chute ranged from 0.24 m in the fish passage notch to 0.61 m in the eddy adjacent to the second
standing wave in the chute. Velocities ranged from 1.0 to 2.25 m/s (meters per second) in the fish
passage notch, with maximum velocities located at the bottom of the initial drop through the notch.
Maximum plunge pool depth was 1.22 m. .

A second set of habitat measurements were taken on October 21 with flows at 170 cfs (Table
13). All measurements were taken in the fish passage notch and chute to determine depths and
velocities that would be encountered by a passing fISh. Approximate locations of measurements taken
during Trip 4 are depicted in Figure 2 to provide a reference for the reader. Depths ranged from
0.21 to 0.43 m in the fish passage notch, with the maximum depth occurring near the center of the
notch (location #3, Figure 2). Depth measured on top of the downstream rip-rap retaining wall was
.0.27 meters. Depths in the chute between the two walls ranged from 0.31 to 0.79 m. Mean depth
in the structure was 0.43 m.

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