Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Coho Salmon: Factors Affecting Species Environment
may be warmer than equilibrium temperature. The effects of this thermal lag diminish
with distance downstream.
The temperature modeling indicated that tributary inputs and meteorological conditions
are the primary temperature drivers throughout the year downstream from the Scott
River. Thus, the ability to control temperature in the lower Klamath River through flow
management at IGD is limited because ambient temperatures and tributary flows
downstream are much larger than those from IGD, depending on season and annual
variability (see earlier Figure 3-16).
During smolt out-migration, the Proposed Action has some effect on temperatures
downstream of IGD; however, temperatures remain within the optimum range for
survival during the majority of the smolt migration for a wide range of flow releases (see
Appendix 3-C), and therefore has a limited effect on smolt survival.
Later in the spring and on through the summer, temperatures exceed tolerable levels and
coho salmon are relegated to thermal refugia throughout most of the main stem or must
migrate into non-natal tributaries (Figure 3-17). During summer, releases from IGD have
little influence on temperatures downriver of the Shasta River. Thus, high temperatures
in the Klamath River sharply limit the rearing capacity for coho salmon in the main stem
during summer, and heat energy balances dictate that releases of any magnitude from
IGD can have little influence below the Shasta River (Cramer Fish Sciences 2007
Technical Memorandum 5).
Figure 3-17. Longitudinal profile of daily maximum, mean, and minimum water temperatures in
the Klamath River for July 1 (top graph), August 1 (middle graph) and September 1 (bottom
graph), as predicted from the temperature model, given 2001 meteorology and tributary flows.
30
25
Temperature (C)
20
15
10
5
0
Shasta River
Scott River
185 175 165 155 145 135 125 115 105
95
85
Salmon River
Trinity River
75 65 55 45 35
25
15
5
Mean
Max
Min
River Mile
1-Jul
225