Biological Opinions - Bureau of Reclamation

Figure 11.16. The average proportion of flow that IGD contributes to downstream sites throughout the year.
Data from stream gages and accretion estimates from Reclamation.
In the Hydrological Effects section, NMFS recognizes Reclamation’s strides to incorporate
elements of the natural flow regime into the proposed action. While flow variability will be
enhanced, and EWA release strategies incorporate key considerations for coho salmon, the
Project consumes water and thus, diminishes flows, particularly channel maintenance and spring
flows, in the mainstem Klamath River when compared to a natural hydrology.
11.4.1.2.1 Spawning Habitat
Coho salmon are predominately tributary spawners and limited coho salmon spawning occurs in
the mainstem Klamath River between Indian Creek (RM 107) and IGD (RM 190), primarily in
side-channels and margins of the mainstem Klamath River (Magnuson and Gough 2006).
Where spawning habitat exists, gravel quality and fluvial characteristics are likely suitable for
successful spawning and egg incubation. As discussed in the Hydrologic Effects section, the
proposed action will reduce the magnitude, frequency and duration of flows between 5,000 and
10,000 cfs relative to the natural hydrograph. Because of storage limitations, the proposed
action will likely have minimal reductions to the magnitude and frequency of flows above
10,000 cfs relative to the natural hydrograph. Therefore, the reduction in magnitude, frequency
and duration of channel maintenance flows under the proposed action will likely reduce
mobilization of fines from spawning gravel. However, the proposed action is not likely to result
in armoring of spawning gravel because the proposed action will have minimal reductions to the
magnitude and frequency of flows above 10,000 cfs relative to the natural hydrograph.
Therefore, the proposed action is likely to reduce some quality of spawning habitat when
spawning gravel becomes filled by fines over time.
Model results in the Phase II report (Hardy et al. 2006) for Chinook salmon spawning habitat
indicate that the IGD to Shasta River reach has at least 80 percent of maximum available
spawning habitat when flows are between 950 and approximately 2600 cfs. While Chinook and
coho salmon spawning habitat preferences (e.g., velocity depth, substrate) vary, coho salmon
spawning habitat preferences fall within the range of conditions selected by Chinook salmon.
Given the abundance of Chinook spawning habitat when flows at IGD are 950 cfs or above and
the low numbers of adult coho salmon spawning in the mainstem, NMFS expects that the
quantity of coho salmon spawning habitat will be suitable under the proposed action.
In average and wetter years (≤45 percent exceedance; Table 11.8), flows under the proposed
action are expected to incrementally increase through the fall/winter period with increased flow
variability. Though spawning habitat for coho salmon is not limited in the mainstem Klamath
River, an increase in flows and flow variability during fall and winter will increase spawning
habitat. As flows increase, suitable spawning habitat becomes more available close to the river
margins. Spawning habitat closer to the margins has a lower risk of scouring during peak
runoffs than locations further towards the middle of the river. In addition, variable flows result
in different areas of the channel bed with high quality spawning habitat for coho salmon, which
increases spawning habitat throughout the fall/winter period. Therefore, the proposed action is
265