Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Coho Salmon: Effects of the Proposed Action on Coho Salmon
Simulation of the Proposed Action showed that a wide range of flow releases
from IGD had little effect on coho salmon smolt production from the Klamath
River Basin (Figure 3-29). The downstream effects from a different set of
meteorology and tributary flows had a far greater effect on smolt production
(approximately a 35 percent increase) than did increasing IGD flows from a 90
percent exceedence to a 40 percent exceedence (approximately a 10 percent
increase). This is a dramatic result, which the modeling revealed was caused by
the inability of flows from IGD to produce suitable rearing temperatures for coho
salmon during summer in the main stem below the Shasta River. If the
temperature model had also been populated with a high runoff year such as 2006,
another substantial increase in smolt production above the 2004 condition would
have been indicated.
Figure 3-29. Total simulated smolt production in year 10 using proposed flows (modeled
2008 to 2018) at IGD for the 2001 and 2004 water year types.
2001 Water Year Type
Simulated smolt production (thousands)
72
70
68
66
64
62
Baseline
Proposed action
0.9 0.8 0.7 0.6 0.5 0.4
Flow exceedence probability
The simulation results (displayed in Figure 3-29) suggest that the population can
endure even in adverse environmental conditions in freshwater. Although smolt
production is less than for the 2004 conditions when compared to 2001 tributary
conditions, the simulated population did not collapse after four generations of
continuous extreme drought (90 percent exceedence releases with 2001
meteorology and tributary flows).
An analysis was also completed for the smolt production under the Proposed
Action and the smolt production under historic operations with a similar water
year. Under all low modeled flow conditions (less than or equal to 50 percent
exceedence) smolt production was 1 to 2 percent greater under the Proposed
Action for conditions set either at 2001 or 2004 (Figure 3-30 and Figure 3-31).
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