Biological Opinions - Bureau of Reclamation

minimizing disease risks, the details of this future process are yet to be developed. Therefore,
except as it relates to minimizing disease risks, the effects of the adaptive management resulting
in potential deviations from the formulaic approach as described in Reclamation’s Final BA (i.e.,
Section 4.3.4 Implementing Environmental Water Account Management; Reclamation 2012) are
not evaluated in our effects analysis.
Therefore, under the formulaic approach of the proposed action, the annual median Project
delivery from all sources by water year is 428,200 acre-ft with a minimum of 178,000 acre-ft and
a maximum of 477,000 acre-ft (Reclamation 2012). Approximately 80 percent of the Project
water delivery is not returned to the mainstem Klamath River (Cameron 2013), while
approximately 20 percent is returned as agricultural tailwater. The Project’s effects to coho
salmon critical habitat result from the Project’s influence of flows at IGD.
11.4.1.1 Hydrologic Effects
The following discussion describes the differences between the Klamath River natural flow
regime under relatively unimpaired conditions defined by the 1905-1913 discharge dataset at
Keno, Oregon and the resulting flow regime from implementation of the proposed action. The
natural flow regime of a river is characterized by the pattern of flow quantity, timing, duration
and variability across time scales, all without the influence of human activities (Poff et al. 1997).
Operation of the Project affects all components of the natural flow regime. In this BiOp, NMFS
recognizes the environmental and human caused factors that have influenced the hydrological
shift from the natural flow regime, including the effects of the Klamath Project. Here NMFS
assesses the Project’s effects on flow volume, magnitude, timing, duration, flow variability, and
channel maintenance flows with consideration of the other factors contributing to the current
Klamath River hydrology. For these analyses, NMFS calculated the 7-day moving average of
the proposed action modeled daily flows at IGD because NMFS believes the 7-day moving
average better represents operationally implementable flows under the proposed action.
However, the proposed action modeled daily discharge at IGD was not converted to a 7-day
moving average for the analysis on channel maintenance flows based on recent clarifications
that Reclamation made to ensure implementation of the proposed action modeled daily peak
flows (Reclamation 2013b).
The proposed action hydrograph at IGD is also compared to the observed hydrograph at IGD for
the 1981-2011 POR because an unimpaired, historic daily discharge dataset at IGD is not
available for comparison. These comparisons to the 1981-2011 POR allow NMFS to evaluate
whether the proposed action will result in a trend of the Klamath River hydrograph towards, or
away from, the natural flow regime. When the proposed action hydrograph at IGD exhibits
better hydrologic conditions (e.g., higher peak flow magnitude, higher flow volume, or enhanced
variability) in the mainstem Klamath River relative to the observed POR hydrograph, the
proposed action trends towards the natural flow regime. Conversely, when the proposed action
hydrograph at IGD exhibits worse hydrologic conditions (e.g., lower peak flow magnitude, lower
flow volume, or diminished variability) in the mainstem Klamath River relative to the observed
POR hydrograph, the proposed action trends away from the natural flow regime. The
characteristics of the Klamath River natural flow regime are important to maintain because those
are the hydrologic conditions that coho salmon evolved under. As the basis for its ultimate
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