7729

• UCREFRP Catalog Number: 7729
• Author: Valdez, R. A., W. J. Masslich and A. Wasowicz.
• Title: Annual Summary Report - 1990\
• USFW Year: 1991.
• Copyright Material: NO

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During 1990, flows of the San Miguel River contributed more to the system than flows from the
Dolores River below McPhee Dam.

Figure 7 presents a hydrograph of mean monthly flows of the Dolores River below the San Miguel
River for 5 years prior to the closure of McPhee Dam (1979-1983), 5 years following closure of
McPhee Dam (1985-1990) and theYampa River at DeerIodge (1979-1983). The data for the Yampa
River, which is a tributary drainage used by Colorado squawfish and is similar to the Dolores River,
and is presented for purposes of giving a relative comparison of the Dolores hydrograph. Normal
peak flows for the Dolores River are substantially less than present in the Yampa River during
runoff.

Temperature

In order to evaluate main channel water temperatures in the Dolores River and the factors that
influence temperatures, the study area was divided into different reaches similar to those used to
evaluate flows with the addition of One reach. These reaches include: 1) the Dolores River below
the confluence of the San Miguel River; 2) the Dolores River above the confluence of the San
Miguel River to Disappointment Creek (immediately above Slickrock, RM 128.7) and; 3) the Dolores
River above Disappointment Creek to Bradfield Bridge.

From Bradfield Bridge (RM 177) downstream to the confluence of Disappointment Creek, the
Dolores River retains basically a tailwater character associated with hypolimnetic releases from
McPhee Dam (RM 185). The river flows through extensive canyon areas which delay and reduce
warming of mainchannel temperatures. Below Disappointment Creek the river channel becomes
more open as the river traverses more valley regions and the floodplain becomes somewhat broader.
Consequently, increased solar radiation and attenuation of the effects of the cold dam releases result
in a significant increase in water temperature. During the summer, main channel temperatures above
and below Disappointment Creek may differ by as much as 40C (Beck 1989). Significant differences
in turbidity also exist between these two reaches (Beck 1989). This difference is probably associated
with the geomorphology of tributary drainages that enter the Dolores River in the two regions.

Main channel water temperatures recorded in the Dolores River during 1990 are presented in Table
29. Temperatures ranged from a low of 3.5 (March 13, 1990) to a high of 27.5 (July 13, 1990).
USGS temperature data for the Dolores River at Bedrock (RM 75) ranged from the low of 30 oC
in July to OOC during many days in winter. Maximum temperature recorded at the Bedrock gage was
33.50C on July 10, 1981. Temperatures in the lower Dolores River are generally moderated by the
larger volume of water and can range from 2~C in July and August to OOC during the winter.
Maximum temperature recorded at the USGS gage near Cisco (approximately 9.5 miles above the
ColoradolDolores River confluence) was 290C on August 14, 1958.

The Dolores River below the confluence of Disappointment Creek (RM 128.7), is unique in
character to the river above Disappointment Creek. Disappointment Creeks represents a distinct
geomorphic transition in the Dolores River system where the river changes character from a cool,
clear stream to a warm, turbid system during the majority of the year. This lower reach of the
Dolores River, with its more turbid and warm character, probably represents the reach most likely
to be utilized by Colorado squawfish. Other native species such as the flannelmouth sucker, bluehead
sucker, roundtail chub and speckled dace are commonly found in the upper reaches where cooler and

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