Biological Opinions - Bureau of Reclamation

Figure 11.11. Proposed action and observed end of September and end of February UKL elevations for water
years 1981-2011.
11.4.1.1.3 Flow Variability
The proposed action includes a formulaic approach to enhance flow variability relative to past
operational approaches. However, the proposed action will continue to contribute to diminished
flow variability relative to a natural Klamath River flow regime (e.g., reduction of incremental
increases of fall and winter base flows). Given the network of dams and operational constraints
of managing flow through multiple reservoirs, achieving relatively unimpaired flow variability is
not feasible.
The early spring period of March and April is generally a period of high flow variability in the
Klamath River. Water storage in UKL and PacifiCorp hydroelectric reservoirs generally peaks
in these months. Rainfall events and sudden increases in snowmelt can result in variable flows at
IGD as Reclamation and PacifiCorp treat hydrological fluctuations as run-of-the-river.
However, in recent years (e.g., 2001-2005) during dry winter and spring conditions, minimum
monthly flows have been implemented, and flow variability has been reduced at IGD even
during March and April. The effects of the proposed action on flow variability will be greatest
proximal to IGD and diminish longitudinally, as tributary accretions contribute to the volume of
water and impart additional flow variability. By early April, contributions from the Shasta River
are expected to be reduced by water diversions for agricultural practices, and tributaries provide
relatively minor contributions for approximately 47 river miles at which point the Scott River
increases flow variability. By mid-June, as Scott River flows decrease substantially from water
diversions and lack of snowmelt, the loss of flow variability at IGD will be evident throughout
the Upper Klamath River reach. With a strong likelihood that current climatological trends and
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