Biological Opinions - Bureau of Reclamation

The central pillar of the proposed action is that water management decisions are linked directly
to real-time hydrologic and water use conditions. For the hydrologic and water use conditions
experienced in the POR, the model simulates water management decisions under the proposed
action and provides a reasonable approximation of outcomes for the different components of the
system. A critical assumption of the effects analysis in this BiOp is that the hydrologic and
water use conditions experienced in the POR, which provided the basis for the simulation of the
proposed action and therefore of the effects analysis, will not change substantially over the term
of this BiOp. If this assumption is violated to the extent that outcomes of implementing the
proposed action do not exhibit central tendency and variability similar to the simulated
outcomes, then operations may fall outside the analytical scope of this BiOp. The kinds of
changes that could produce such a result include, but are not limited to:
Sequencing of water years in terms of relative wetness and dryness. For example, two 3-
year sequences of extremely dry – extremely dry – relatively wet (1991 – 1992 – 1993)
and extremely dry – relatively wet – extremely dry (1992 – 1993 – 1994) exist in the
POR, have been simulated, and are evaluated in this BiOp. However, a sequence of three
back-to-back extremely dry years does not exist in the POR, has not been simulated, and
has not been evaluated in this BiOp. Because the third year in a sequence of extremely
dry years is likely to have outcomes more severe than what has been evaluated in this
BiOp, such a sequence would be considered to be outside the scope of the BiOp.
Declines in base flows during the July through September period.
Continued shifts in the timing of spring run-off toward earlier in the year.
Shifts in the pattern of consumptive water use within the Project, or the pattern or
magnitude of water use above UKL.
Shifts in the pattern or magnitude of net accretions between Link River Dam and Iron
Gate Dam.
Shifts in the pattern or magnitude of flows passing Harpold Dam.
Changes to the elevation-capacity relationship for UKL.
For this BiOp, we assumed the PORs for the hydrology of the three primary Project reservoirs
represent the range and distribution of elevations that are reasonably likely to occur over the 10-
year consultation term (May 31, 2013 to March 31, 2023). However, we are also aware that, if
trends continue, climate may be somewhat drier on average during the next 10 years than for the
entire POR because drier conditions have prevailed recently and average inflows to UKL
(1,081,000 acre-feet) during the decade between 2002 through 2011 are over 10 percent less than
average inflow (1,246,000 acre-feet) during the entire POR.
We assume the following regarding the volume and timing of hydrologic data critical to the
KBPM and implementation of the proposed action:
Flow in the Williamson River and net inflow to UKL will be similar in magnitude,
pattern, and sequence to that observed in the POR.
Flow (return flow or direct release) from the east side to the west side of the Project will
be within the ranges observed during the POR, and appropriate for water year conditions.
Accretions to the Klamath River between Link River Dam and Iron Gate Dam will be
within the ranges observed during the POR, and appropriate for water year conditions.
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