Biological Opinions - Bureau of Reclamation

Table 4.10. July, August, and September Iron Gate Dam maximum flow targets.
EWA Volume
(acre-feet)
July(cfs)
August
(cfs)
September
(cfs)
320,000 1,000 (28.3 m 3 /sec) 1,050 (29.7 m 3 /sec) 1,100 (31.2 m 3 /sec)
1,500,000 1,500 (42.5 m 3 /sec) 1,250 (35.4 m 3 /sec) 1,350 (38.2 m 3 /sec)
> 1,500,000 1,500 (42.5 m 3 /sec) 1,250 (35.4 m 3 /sec) 1,350 (38.2 m 3 /sec)
Intermediate values are obtained by linear interpolation
4.2.3.2.4 Flood Prevention and Environmental Water Account Management
Flood releases from Link River Dam occur any time UKL elevations exceed, or appear likely to
exceed, elevations that put UKL levees at risk of failure or being overtopped. During the
irrigation season, the majority of these releases occurs in March, April, and May in average to
wet years. However, flood prevention releases can occur later in the water year, and may also
occur in drier years under certain conditions such as rain on snow events. Flood prevention
releases in the spring/summer are counted against the EWA. In some cases, flood prevention
releases can be so large and account for such a high proportion of the total EWA that the
remaining EWA is not adequate to provide acceptable habitat in the Klamath River for listed
species for the remainder of the spring/summer season. To protect against this scenario, the
EWA is increased when flood prevention releases from Link River Dam exceed 22 percent of the
total EWA by June 1. The volume of remaining EWA each month is determined based on the
following:
1. If the total flood prevention releases that have occurred by June 1 exceed 22 percent of the
June 1 EWA calculation, the remaining EWA is reset to 25 percent of the total June 1 EWA.
2. If the total flood prevention releases that have occurred by July 1 exceed 22 percent of the
June 1 EWA calculation, the remaining EWA is reset to 18 percent of the total June 1 EWA.
3. If the total flood prevention releases that have occurred by August 1 exceed 22 percent of the
June 1 EWA calculation, the remaining EWA is reset to 13 percent of the total June 1 EWA.
4. If the total flood prevention releases that have occurred by September 1 exceed 22 percent of
the June 1 EWA calculation, the remaining EWA is reset to 7 percent of the total June 1
EWA.
The formulaic approach for EWA distribution using Williamson River as a hydrologic indicator
is designed to consider and account for key ecological objectives for UKL and the Klamath
River. Although expected to be rare, there may be circumstances or emergency situations where
it is desirable or necessary to deviate from this approach. In addition, there may be specific
ecological objectives that water resource managers need to address that can only be achieved by
deviating from the EWA distribution methodology. Deviations are most likely to be alterations
in the magnitude or duration of flow to address urgent ecological concerns such as mitigating
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