Biological Opinions - Bureau of Reclamation

Figure 11.12. Number of days per water year that exhibit daily flow changes of 30 cfs or higher for the
proposed action and Observed IGD daily discharge.
In water years 1994 and 2005, the observed IGD discharge exhibits daily variability of 30 cfs or
higher for a larger number of days. However, in these years, the variability demonstrated in the
observed daily discharge is often a result of management decisions and is unrepresentative of
hydrologic conditions, as evidenced by the Williamson River hydrograph in water year 1994
(Figure 11.13). The Williamson River is a reasonable indicator of hydrologic conditions in the
upper Klamath Basin. Although affected by water diversions above UKL by off-project water
users in the spring and summer, the Williamson River still maintains a very strong correlation
with UKL net inflow (Garen 2011). Water year 1994 is one of the driest years on record and yet
the observed IGD flows were highest during the October through January period when the
Williamson River was at base flow (Figure 11.13). Observed flows at IGD from March through
June 1994 were among the lowest flows of the year, whereas observed flows at the Williamson
River indicate this time period is when flows should be highest. In water year 1994, the greatest
variability and some of the highest flows in the observed IGD discharge occur in the summer
months when Williamson River flows are receding to base flow and natural variability is
minimal (Figure 11.13). The proposed action hydrograph more accurately represents natural
hydrologic conditions as it more closely mimics the shape and relative magnitude of the
Williamson River hydrograph (Figures 11.13 and 11.15). Proposed action flows are dictated by
daily calculations based on hydrologic indicators in the basin including the Williamson River.
Although the proposed action has less daily flow changes of 30 cfs or higher than the observed
flows in 1994, the variability coincides with changing hydrologic conditions and is more
representative of the Klamath River natural flow regime, which is beneficial to coho salmon
(Figure 11.13).
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