Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Coho Salmon: Effects of the Proposed Action on Coho Salmon
Effects on ESU Abundance
Population abundance is an important criterion for VSP because large populations
exhibit a high degree of resilience (McElhany et al. 2000). To assess the impacts
of the Proposed Action, simulations for 10 years into the future where conducted,
with environmental conditions fixed at either 2001 or 2004 meteorology and
tributary flows downstream of IGD. These are the two years for which the
hydrodynamic temperature model was fully populated with meteorological and
tributary flow data for the Klamath River below IGD. Although both flows at
IGD during 2001 and 2004 were both below normal (Figure 3-28) those same
years produced 95 percent and 55 percent exceedence flows from the Salmon
River, respectively.
Figure 3-28. Depictions of the flows at IGD during 2001 and 2004, the historical (1961 to
2006) 50 percent exceedence, the modeled (2008 to 2018) 50 percent exceedence
(smoothed), and the proposed minimum flows (dry water year flows as outlined in NMFS
2002 BO).
3,000
2,500
Average Monthly Flow at IGD (cfs)
2,000
1,500
1,000
500
0
Historical 50% Exceedence (1961-2006)
2001
2004
Dry Yr BO Minimum
Modeled 50% Exceedence (2008-2018)
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
In these simulations, total smolt production represented coho salmon abundance
because smolts are the final life stage in freshwater. Returning adults might also
be affected by pre-spawning mortality in freshwater, but such effects would be
reflected in the abundance of smolts the next generation. Smolt production in
year 10 was used because it represents the fourth generation of naturally produced
coho salmon smolts that would have resulted from the fixed environmental
condition being simulated. Such simulations with fixed environments represent
extreme cases to reveal how good or bad production will become after extended
exposure to the same condition. As an illustration of the extreme nature of this
simulation, 2001 was a 95 percent exceedence year for the Salmon River,
meaning that it would only be expected to recur once in every 20 years. Thus, a
10 year simulation of 2001 conditions represents a dry year sequence that has a
very small chance of ever occurring.
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