8167

• UCREFRP Catalog Number: 8167
• Author: Nehring, R. B.
• Title: Distribution and Abundance of the Fish Fauna in the Dolores River From McPhee Reservoir Downstream to the Dove Creek Pump Plant.
• USFW Year: 1993.
• USFW - Doc Type: Montrose, Colorado.
• Copyright Material: NO

INTRODUCTION

An unusually heavy snowpack in the Colorado's southern San Juan mountains
during the winter of 1992/1993, resulted in the second largest spring run-off in
the Dolores River basin since McPhee Reservoir became operational in April 1984
(see Table 1). In late-November 1992 the U.U. Bureau of Reclamation -Durango
Projects Office (USBOR-DPO) determined the bottom outlet gates in McPhee Dam
needed maintenance that required removal. Moreover, use of the surface spillway
gates would be required to control the rate of filling of McPhee Reservoir once
the spring run-off began.

Use of the spillway gates began in mid-March and continued until late May
1993, when repair and reinstallation of the bottom release gates had been
completed. The managed spill (through the bottom outlet gates) continued into
the first week in July. Large blocking seines were installed in McPhee Reservoir
in front of the spillway gates a few weeks after the surface spill began to
minimize escapement of fish from the reservoir into the river below. However,
it was suspected that some fish from the reservoir would escape over the spillway
or through the bottom outlet works during the managed spill.

In order to assess the level of fish escapement from McPhee Reservoir into
the Dolores River downstream, the USBOR-DPO requested that the Colorado Division
of Wildlife (CDOW) cooperate in an extensive electrofishing survey of the river
below the dam. The primary purpose of the survey was to assess the distribution
and abundance of fish species in the Dolores River from McPhee Dam to the Dove
Creek Pump Plant, some 30 river miles downstream. This report summarizes the
results of that survey.

Table 1. Dolores River flow regime cubic feet/second (cfs) below McPhee
Reservoir versus acre-feet (AF) inflow/water year, 1984 to 1993.

Winter flows" Spill period & range Summer flowsb
Water Inflow
year AFxlOJ Mean Range Dates Range Mean Range
1984 580.3 -- 4/10-7/2 700-3825 172 54-656
1985 611.0 167 32-1065 4/1-6/25 187-3700 69 50-187
1986 572 .3 59 49-100 4/2-6/23 600-4461 131 77 -501
1987 589.2 223 71-600 4/4-6/27 600-3324 163 46-269
1988 259.2 78 70-83 5/2-6/7 194-1201 79 77-81
1989 263.1 79 49-81 4/6-5/14 440-1001 82 70-107
1990 142.5 69 20-80 -- 0 35" 20-75
1991 293.0 31 27-39 5/13-5/27 125-800 61 33-71
1992 351. 9 32 .29-38 - 4/15-6/19 151-3009 75 55""'102
1993 598.2d 85 30-680 3/17-7/5 126-4140 132d 90-643
W~nter tlow data ~s tor October T - March .31 tor water year.

b Summer flow period data is for July 1 - September 30.
o Summer flow period for 1990 is April 1 - September 30.
d Estimated for 1993 water year, 10/1/92-9/30/93.

METHODS

Except for the reach of the river between Bradfield Bridge and the BLM raft
launching area (approximately 0.5 river miles), the entire river from the USFS
Metaska Day Use Area near McPhee Dam to the Dove Creek Pump Plant was surveyed
twice with an electrofishing raft. Electrofishing operations on the river
segment from the BLM raft launch site below Bradfield Bridge to the Dove Creek

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