Biological Opinions - Bureau of Reclamation

Although the volume of Project water use may be different from the POR, particularly in
years drier than average, the pattern of water use will be similar to the pattern observed
during the POR.
We further assume Reclamation will incorporate the previous year’s hydrologic data into the
KBPM by March 31 each year to ensure the model remains current and reflects hydrologic
trends. Data to be incorporated into the model annually include:
UKL calculated daily net inflow (KBPM SV file variable I1_raw)
UKL 3-day moving average net inflow (KBPM SV file variable I1)
UKL cumulative inflow index (KBPM SV file variable)
Cumulative precipitation index (KBPM SV file variable)
Williamson River daily average flow (KBPM SV file variable)
Lake Ewauna accretions (KBPM SV file variable I10)
Keno Dam to Iron Gate Dam accretions (KBPM SV file variable I15)
Flow diverted from the Lost River to the Lost River Diversion Channel at Wilson Dam
(KBPM SV file variable I91)
Area A2 winter runoff (KBPM SV file variable I131)
NRCS forecasts for the Williamson River and UKL
Project and Lower Klamath Lake NWR daily diversions and return flows
8.1.3 Sideboards for the Effects Analysis of Hydrologic Conditions
Our effects analysis for proposed management of UKL water levels is based on modeled output
from the KBPM of the proposed action using hydrologic data from the POR. Modeled weekly
UKL elevations for the POR are presented in tabular and graphical form in Appendix B. For
Clear Lake and Gerber Reservoir, we compared minimum elevations and lake-level probability
tables to the conservation needs of the species. For Tule Lake, the comparison was based on the
proposed seasonal lake minimums. It is possible, but unlikely, that hydrologic conditions outside
of the range, distribution, and sequence of conditions modeled for the proposed action could
occur during the 10-year term of the proposed action. We cannot state with absolute certainty
what hydrologic events will occur in the future, but we conclude that the past is the best predictor
of the near future, (i.e., the next 10 years) and, therefore, we assume rare events in the past will
be rare in the near future.
Reclamation’s BA (Reclamation 2012) analyzed the hydrologic effects of the proposed action on
LRS and SNS in UKL up to the 95 percent exceedance of lake elevations. As used by
Reclamation, the 95 percent exceedance means that on any given date a specific lake elevation
would be exceeded 95 percent of the time. This is equivalent to stating that there is a 95 percent
probability of exceeding that specific lake elevation on a given date. For our analysis, we
analyzed the effects of the proposed action over the full range of modeled results for each month,
regardless of the probability of observing a specific elevation in the future. End-of-month
elevations for Clear Lake and Gerber Reservoirs are presented in Appendix B. UKL end-ofmonth
elevations are presented in Table 8.1 of section 0, Effects of the Action, of this BiOp.
The USFWS will evaluate whether implementation of the proposed action results in expected
UKL elevations for each month of the year, based on the scatter of UKL elevations simulated by
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