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Water temperature is very
important to salmon and steelhead survival. While the temperature range required
by each species varies, all salmonids need cold water. Temperature affects success
in spawning, survival of eggs and alevin, growth rate of young fish, and mortality.
During the summer months when stream temperatures rise, Battle Creek supports
adult spring-run chinook salmon, as well as the eggs of those fish, once they
have spawned. Eggs of the winter run chinook are still incubating in the gravel
at the beginning of summer. Populations of both spring-run and winter-run chinook
populations in the Sacramento River system have declined to levels that have
generated concern.
Salmon eggs are especially
sensitive to temperatures. They require colder water than do juveniles and adults,
and because they are unable to move out of warm water reaches, they are the
most vulnerable when stream temperatures rise. Pre-spawning adults need temperatures
below 61 degrees F to insure their vitality. Warm water can cause infertility
and mortality before spawning is achieved. Adult spring-run chinook arrive in
Battle Creek in March through May, and they hold in the stream for several months
before they spawn. Chart showing temperature
tolerance ranges for different life stages.
Graphics by CH2M HILL
Several factors influence water temperature in Battle Creek. The upper reaches
are naturally cooler because of the elevation. The North Fork flows through a
steep canyon, which helps shade the water. Numerous springs continually feed cold
water into the stream. The South Fork is fed by fewer springs and is exposed to
warmer air temperatures and more direct exposure to sun as it flows through a
less confined valley. As would be expected, the lower reaches of the South Fork
are warmer than in the North Fork.
Operation of hydroelectric
facilities also influence water temperatures in Battle Creek. Reduced stream
flow resulting from diversions caused the water left in t he stream to warm.
Shunting water between the power facilities may also cause stream warming if
the water flows in open canals for some distance.
Water temperature data for the McCloud River and Little Sacramento River, where
winter-run chinook salmon used to spawn before construction of Shasta Dam, indicate
that average June and July water temperatures were less than 60°F and were
usually less than 58°F.
References
Armour,
C. L. 1991. Guidance for evaluating and recommending temperature regime
to protect fish. Biological Report 90(22). US Fish and Wildlife Service. Ft.
Collins, CO. 13 pp. [316kb]**
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