Biological Opinions - Bureau of Reclamation

8 EFFECTS OF THE ACTION ON LOST RIVER SUCKER AND SHORTNOSE
SUCKER
8.1 Analytical Approach
8.1.1 Use of the Period of Record Hydrograph as a Tool to Analyze Project Effects
Because the proposed action is storage and delivery of water for Project purposes, analyzing
hydrologic data, such as water levels in LRS and SNS habitats, is essential to our analysis of
effects. However, because there is no way to know with certainty what future water conditions
will be, for purposes of this analysis, we have relied upon historical data (i.e., the POR) in
simulations to understand the likely range and distribution of elevations in Project reservoirs
over the proposed 10-year term of Project operations. To be useful, the POR needs to be
sufficiently long to capture a broad range of conditions and also needs to include recent data to
capture any current trends. For this consultation, the POR hydrology data selected for Clear
Lake and Gerber Reservoir were for calendar years 1902–2012 and 1925–2012, respectively.
The POR hydrological data set for UKL relied upon in this analysis is the 31 years between
October 1, 1980, and September 30, 2011. The shorter time period for the UKL POR was
chosen because relevant data, specifically the reconstructed annual NRCS forecasts of water
supply, which are necessary for modeling purposes, were only available beginning in the 1981
water year. Nevertheless, we conclude this POR sufficiently captures recent climatic trends and
current water-use conditions, while also including a broad distribution of dry, average, and wet
years.
Because Tule Lake is primarily a sump and gets most of its water from agricultural return flows,
past water levels have been managed close to the minimum lake levels identified in the proposed
action to reduce the risk of flooding. As a result, the POR water levels in Sump 1A of Tule Lake
are less variable when compared with the Project’s three primary water supply reservoirs: UKL,
Clear Lake, and Gerber Reservoir.
8.1.2 Use of the KBPM Model as a Tool to Analyze Project Effects on Water Levels
To analyze potential effects of the proposed action, Reclamation and the Services used the
KBPM to identify Klamath River and UKL hydrographs that would have occurred if the
proposed action had been implemented at the start of the 1981 water year. The hydrographs and
other modeled output are also used by the Services to anticipate likely future lake and river
conditions in water years similar to those occurring in the POR. KBPM is based on Water
Resource Integrated Modeling System software (WRIMS), a broadly accepted, generalized
water-resources modeling software designed for evaluating river-basin scale water management
alternatives. KBPM was developed jointly by Reclamation and the Services specifically for this
consultation, and included input from Klamath Basin Indian tribes and the Klamath Project
Water Users Association. A model is not available for the east side of the Project (i.e., the Lost
River subbasin, including Clear Lake, Gerber Reservoir, and Tule Lake), so reservoir-specific
water balance models based on the POR were used instead. For a detailed description of the
KBPM model, see Appendix 4A in the BA (USBR 2012) and the description of the proposed
action in the BA and in this BiOp.
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