Draft EIS_072312.pdf - Middle Fork American River Project ...

20120723-4002 FERC PDF (Unofficial) 07/23/2012
that have evolved in streams with less seasonal variation in flows (Marchetti and Moyle,
2001). All of the above changes that restore some natural seasonal and year-to-year
variability in instream flows would be expected to enhance conditions for the native
aquatic species that evolved under such dynamic conditions, providing benefits to aquatic
macroinvertebrates and fish.
The proposed and Alternative 1 minimum instream flows are also designed to
provide temperatures that support hardhead spawning. Termination of diversions from
Duncan Creek, North Fork Long Canyon Creek, and South Fork Long Canyon Creek
during July through September should result in no change in rearing habitat for rainbow
trout adult or juveniles during the summer and fall because under existing conditions, no
diversions typically occur during this same time frame. Using whole numbers for
designated minimum flows, as is done for all Alternative 1 values, is more practical as a
standard against which compliance can be monitored than the occasional 0.5 cfs standard
that PCWA proposes.
We see no reason that a 5-day grace period for releasing instream flows as
proposed by PCWA is needed. If a new license specifies a date when the minimum flow
to a project stream reach should change, PCWA could plan appropriately to ensure the
flows are released on the designated day as provided for in Alternative 1. It may be
infeasible (e.g., because of difficulty in continuously monitoring gaging data, potential
errors in reading flow, and time needed to adjust flow releases) for PCWA to maintain
instantaneous flows above the minimum flows at all times, and compliance based on
maintaining daily average flows above the minimum flows, as specified in Alternative 1,
would be achievable. Allowing daily average flows that are only 90 percent of specified
instantaneous flows to be compensated by over-releases within 3 days to achieve the
designated flow, as proposed by PCWA, is inconsistent with the reasons for an
instantaneous minimum flow, which is to ensure a constant base flow for aquatic habitat
protection and enhancement. It is reasonable to have specific time frames for
implementation of instream flow requirements where facility modifications and
construction are needed and this would enhance Commission staff’s ability to track
compliance with interim minimum flows (those required until infrastructure
modifications are complete) and permanent minimum flows.
Minimum flows that would be protective of aquatic habitat during project
operations would be similarly protective of habitat during planned and unplanned
outages, and the Alternative 1 approach to maintaining minimum flows in the bypassed
reach provides this level of assurance while allowing for some reductions under certain
circumstances based on limitations of the project. The proposed minimum flows would
be less than the Alternative 1 minimum flows during outages, and during unplanned
outages, would be constant for up to 48 hours regardless of the timing; therefore, the
proposed flows would not account for changes in flow releases that would occur during
the summer.
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