8141B

• UCREFRP Catalog Number: 8141B
• Author: Wydoski, R. S. and W. T. Helm.
• Title: Effects of Alterations to Low Gradient Reaches of Utah Streams
• USFW Year: 1980.
• USFW - Doc Type: Summary.
• Copyright Material: NO

SUMMARY REPORT

The effects of various stream channel alterations on fish and macroinverte-
brates were assessed for low gradient reaches of two streams (Blacksmith Fork
and Logan Rivers) in the floodplain of Cache Valley in northern Utah. Both
streams have national reputations as fine trout streams and are important among
the 97 kilometers (60 miles) of prime trout stream habitat that still remain in
Utah. This study involving stream channel alterations from agricultural prac-
tices compliments studies on the effects of stream channel alterations in other
parts of the Intermountain West that were done in steep, canyon areas mainly
due to construction of highways and railroads.

The specific objectives of the study were: (1) To follow physical changes
in the streambed after various types of alterations; (2) To estimate populations
and production of fish and invertebrates in altered and unaltered reaches after
different intervals of time; (3) To relate physical changes in the streambed
to biological responses; and (4) To provide suggestions that will help minimize
the effects on fish and wildlife from alterations to stream habitat.

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The climate of this area is semi-arid with about 41 cm (16 in) of annual
precipitation. The average monthly air temperature for the year is 8.6 C
(47.3 F) with a low in January of about -4.1 C (24.6 F) and a high in July of
21.6 C (71.2 F). The streamflcws of the Blacksmith Fork and Logan Rivers are
primarily governed by runoff from the snowpack as the air temperatures increase
from mid-April to mid-July and percolation from groundwater. Th2 drainagz area
of the Blacksmith Fork River as it enters Cache Valley is 694 km (268 mi ).
The average daily discharge for 62 years was 3.65 m3jsec (129 ft3jsec) with
an annual production of 115 hmjyr f93,460 acre-feetjyr). The drainage area for
the Logan River is ~54 km2 (214 mi ). The average daily discharge for 62 years
was 3.40 m3 (120 ft jsec) with an annual production of 107 hmjyr (87,000 acre-
feetjyr). A volume of water equal to or exceeding the average daily discharge
is diverted from the streams for agricultural irrigation before the streams
enter Cache Valley. In general, the water temperature of the Blacksmith Fork
River was slightly warmer than the Logan River. Specific conductance of
these streams ranged between 345-645 incromhos during 1975-76; waters with
similar conductivity have been reported to be quite productive for trout.

Brown trout (Salmo trutta) and mountain whitefish (Prosopium williamsoni)
populations were studied intensively since these species are the principal
fish in the Blacksmith Fork and Logan Rivers. In addition, the mottled sculpin
(Cottus bairdi) are abundant but were not studied because of the problems
involved in making quantitative population estimates of this species. Cutthroat
trout (Salmo clarki), rainbow trout (Salmo gairdneri), and speckled dace
(Rhinichthys osculus) are found occasionally in the study areas of these rivers.
In early sp~ing, large .Utah. sucke'lll5;{:.~Cato~~~s arden~) migrq,t~ into and through
the study sltes, sometlffies ln largenumbet'~f,br spawnlng. ~rln~ the summer,
small numbers of carp (Cyprinus carpio) a.l1d the Utah chub ((rilaatratia) were
found in the study sites; these species move upstream fromCutlar Reservoir as
the water temperature increases during low streamflows.

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