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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less turbid conditions exist. The Disappointment, Creek transition may not be as significant to these
species.

Habitat Availability/Channel Morphology

A general description of channel morphology and gross habitat structure of the Dolores River was
presented by Valdez et al. (1982). This description included maximum and average depths, channel
width and a general description of floodplain and channel characteristics. Results of the present study
indicate that little change in gross physical habitat occurred in the Dolores River since 1982. A
generalized description of habitat and channel morphology for each subreach of the study area is
presented below.

Subreach I (RM 0.0 - 22.7) This subreach includes a wide variety of substrates, channel
configurations and habitat types. From the confluence (RM 0.0) to approximately RM 12.0 the river
is relatively shallow, with numerous runs interspersed with cobble riffles, small rapids and pools at the
mouths of tnoutary drainages. Substrate ranges from large boulder and rubble fans at the mouths
of side canyons to cobble and gravel in riffle areas and finer sands and silt in slow runs and other low
velocity habitat. Above RM 12.0 to Stateline Rapid (RM 22.7) the river flows through a narrow
canyon. The gradient is slightly higher in this area and more rapid and pool habitat is available.
Maximum depth measured in this area was 13 feet in a pool at RM 15.9. Approximate depths
observed for various habitats at low flows range from 6 to 8 feet in pools, 2 to 4 feet in runs and 0.5
to 3 feet in riffles. Channel widths of 33 to 100 feet reported by the Valdez et al. (1982) are
consistent with those observed during 1990.

Subreach IT (RM 22.7 - RM 41.3) This subreach is characterized by a relatively wide floodplain and
more braiding of the channel. A wide range of habitats and substrates also exist in this subreach
similar to Subreach 1. Areas of long slow runs are prevalent, interspersed with cobble riffles and
small alluvial rapids associated with the mouths of side canyons. Channel widths of 82 to 100 feet
and a mean depth of 3.3 feet with a maximum depth of 11 feet was reported by Valdez et at (1982)
for this reach. One perennial tributary (West Creek) flows into the Dolores River from the east at
RM 31.2.

Subreach ill (RM 41.3 - RM 64.4) The floodplain becomes more constricted in this subreach as the
river flows through narrow deep canyons. Several small rapids occur at the mouths of side canyons,
but generally the reach is characterized by a series of riffles, pools and long slow runs. Numerous
pools with depths greater than 10 feet were identified in this reach. Valdez et al. (1982) reported
6.5 and 33 feet as the mean and maximum depths, respectively for this reach. They also measured
channel widths of 82 to 115 feet. Perennial tributaries in this reach include Blue Creek (RM 44.3),
Roc Creek (RM 54.7) and the San Miguel River (RM 64.4).

Subreach IV (RM 64.4 - RM 74.8) This subreach is composed of two distinct areas including a short
narrow canyon above the San Miguel confluence and a reach where the Dolores River traverses the
Paradox Valley. The canyon reach is composed of a continuous series of shallow riffles and runs.
With the exception of a large deep pool immediately above the confluence of the San Miguel River,
pool habitat is very scarce in this reach. Rubble, cobble and boulders are the predominant substrates.
Where the Dolores River traverses Paradox Valley, the river is characterized by a wide floodplain,
low velocities and fine substrates. Average depth in this reach is approximately 1 to 2 feet. River
widths of 80 to 100 feet were reported by Valdez et a1. (1982).

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