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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Subreach V (RM 74.8 - 124.7) This subreach encompasses several narrow canyon reaches, including
one canyon 32 miles in length. The river also traverses several small valleys in this subreach. In the
canyon areas the river is generally characterized by a series of riffles, pools and slow runs. Several
small rapids are located at the mouths of tributary canyons. Silt is the predominant substrate in areas
with low velocities, with cobble more prevalent in riffle and rapid areas. Rubble and boulder
substrates are associated with the alluvial outwash of tributary canyons. Maximum depth measured
in this reach was 11 feet La Sal Creek, which flows perennially, enters the Dolores River from the
west at RM 79.5.

Potential Spawning Habitat

Thirteen potential Colorado squawfish spawning sites were identified on the Dolores River in 1990.
Classification of these areas as potential spawning sites was based on criteria previously described,
including the presence of deep pools and eddies in proximity of and interspersed with cobble riffle
and run habitat. Three of these sites were selected as being characteristic of potential spawning sites
in the Dolores River. Detailed maps of these sites are presented in Figures 8-10. Since all mapping
in 1990 was conducted during low flows, emphasis was placed on characterizing substrate sizes and
embeddedness at each of the sites. Efforts will be made to revisit the sites in 1991 when
temperatures and flows are in the range normally associated with Colorado squawfish spawning.

Nursery Habitat

Backwater densities on the Dolores River ranged from 0.4 to 0.8 backwaters per mile at flows
observed during 1990. Backwaters ranged in size from 14 m2 to 3000 m2. Maximum depths of
backwaters ranged from 6 inches to 4 feet. Substrates were generally composed of organic fines, silt,
sand and cobble. The majority of backwaters were formed from side channels that had stopped
flowing due to a drop in water level. Highest backwater densities were generally found in Subreaches
II and ill.

Other potential nursery habitats included isolated pools and "trickle fed" side channels. Isolated pools
were generally not common in the Dolores River, although several large isolated pools were located
that were providing habitat for an array of both native and non-native species. "Trickle fed" side
channels were also identified as a potential nursery habitat. This type of habitat is characterized by
a side channel that has been isolated from inflow except for a small trickle of water generally flowing
through cobbles at the upstream end. Current was generally not perceptible and temperatures
patterns were similar to those observed in backwaters. This habitat type was common throughout
much of the study area.

4.3.2 Chemical (Water Quality)

Water quality samples collected in the Dolores River during 1990 represent grab samples collected
at specific points in time. Because of the variable nature of the Dolores River in terms of flows andswater quality, these water samples may not be indicative of the worst or best case
water quality
scenario. Based on characteristics of the water during sample times, it is suspected that flood events
or spates, particularly those associated with runoff of high intensity summer storms, may manifest
water quality problems that are not present at other times. Water quality data for Trips 1 through
3 are presented in Tables 30-32.

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