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

20120723-4002 FERC PDF (Unofficial) 07/23/2012
Natural barriers in the tributaries to the project streams limit the ability of fish to
use these streams. Sixteen of the eighteen surveyed tributaries to project-affected reaches
had natural barriers near their mouth that prevented upstream access by fish (see figure
3.3.2-6). Two tributaries to the peaking reach provide accessible habitat for fish: North
Fork of the Middle Fork American River and the downstream-most 1.5 miles of
Otter Creek.
All major inlets to reservoirs and diversion pools are free from natural or
reservoir-created fish passage barriers except the Hell Hole reservoir inlet and the South
Fork Long Canyon Creek diversion inlet (see figure 3.3.2-6). At the inlet to Hell Hole
reservoir, there are five natural channel barriers in the Rubicon River below the Hell Hole
reservoir high water mark (i.e., river barriers when the reservoir was not at full pool).
There are also three natural impassable barriers in the Rubicon River just upstream of the
reservoir (above the high water mark) that preclude upstream passage in the river
regardless of reservoir elevation. There is also a potential natural stream barrier on Five
Lakes Creek about 13 to 14 feet below the Hell Hole reservoir high water mark. The
South Fork Long Canyon diversion pool creates a gravel delta at the inlet. When the
diversion pool is full, fish passage out of the diversion pool is possible. When the
diversion pool is not full, a critical riffle is exposed on the gravel delta that creates a
potential barrier to upstream movement from out of the diversion pool area into the
stream. However, this only occurs when the diversion is not diverting (e.g., during the
summer and fall) and, at that time, there is only a small shallow pool in the bottom of the
diversion pool area.
Riverine Fish
Fish populations were surveyed during 2007–2009 at sites on the bypassed
reaches, peaking reach, and upstream of project diversions and dams to identify the
spatial distribution, condition, and abundance of fish species and determine the upstream
distribution of trout, hardhead, and Sacramento pikeminnow. The information herein is
based on the 2007–2009 survey results.
Species distribution in the study area reflects fragmentation imposed by water
temperature and fish barriers. Trout are the most widely distributed of the 15 species of
fish observed at the study sites. Average water temperatures recorded in August indicate
that temperatures remain within the range suitable for trout in most of the bypassed
reaches and the peaking reach (e.g., average monthly water temperature