Biological Opinions - Bureau of Reclamation

Figure 8.5. UKL elevations at the end of February (kaf = thousand acre-feet).
In February, water years 1982, 1993, and 2006 are considered outliers because the UKL
elevation was less than expected for the cumulative inflow in those years, based on threshold
shown in Figure 8.5. Circumstances for these years were similar to those described for January.
In similar situations during implementation of the proposed action, Reclamation will consult
with the Services regarding reasons for the lower than anticipated UKL elevations. The Services
and Reclamation will determine if UKL is on a trajectory to fill later in the winter, based on
current and forecasted conditions or if adaptive management actions must be taken. Therefore, if
the cumulative net inflow to UKL since October 1 is greater than 550,000 acre-feet, no threshold
applies if the Services and Reclamation agree that UKL is on a trajectory to fill later in the
winter, or adaptive management actions will result in sufficient UKL elevations in the spring.
For cumulative net inflow values less than 362,000 acre-feet since October 1, the minimum UKL
elevation is 4,141.07 ft (1,262.20 m).
For cumulative net inflow values between 362,000 and 447,000 acre-feet, the equation
determining the UKL elevation threshold = 0.006125x + 4138.8493 where x = the cumulative
net inflow into UKL since October 1 in thousand acre-feet.
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