Biological Opinions - Bureau of Reclamation

substantially reduced. The modeled data for Iron Gate, California, clearly shows a decrease in
the magnitude of peak flows, a 2-month shift in timing of flow minimums from September to
July, as well as reduction in the amount of discharge in the summer months. By truncating the
range of flows that led to diverse coho salmon life history strategies, changes in the annual
hydrology likely adversely affected coho salmon populations.
Although monthly flow values can be useful for general river-basin planning, they are not useful
for ecological modeling for river habitats because monthly average flows mask important flow
variability that likely exist only for a few days or less (NRC 2008). In order to address this
shortcoming in analyzing monthly flow data, Figure 11.2 is presented to examine daily historical
and current Klamath River discharge patterns at Keno, Oregon.
Figure 11.2. Average daily Klamath River discharge at Keno, Oregon, during three different time periods.
The 1905 to 1913 dataset represents historical, relatively unimpaired riverflow, while two more modern time
periods represent discharge after implementation of the Project.
Data in Figure 11.2 are averages of daily discharge across years for three different time periods.
The 1905 to 1913 period represents historical unimpaired flows in the Klamath River at Keno,
OR. However, diversions to the A Canal of Reclamation’s Klamath Project began in 1906, so
the 1905 to 1913 period does not represent completely unimpaired flow, rather the closest
approximation to unimpaired flows. Two more modern periods, 1960 to 1977 and 1985 to 2006,
can provide some insight into the effects of Reclamation’s Klamath Project. These time periods
were chosen because the climatic patterns cycled through a cool phase (increased snowpack and
streamflow) from the mid-1940s to 1976 and through a warm phase (decreased snowpack and
streamflow) from 1977 through at least the late 1990s (Minobe 1997, Mote 2006). By using
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