Biological Opinions - Bureau of Reclamation

Figure 11.19. Conceptual model for the effect of flow on water quality in the mainstem Klamath River. The
model only shows the most relevant factors that affect water quality (Asarian and Kann 2013).
Temperature modeling of the mainstem Klamath River by Perry et al. (2011) shows that
increasing flows out of IGD by as much as 1000 cfs in the spring decreases water temperatures
on the mainstem Klamath River by only up to 0.5 °C at either the Shasta River or the Scott River
confluence (Appendix F). Since the total net Project reductions (i.e., the total Project diversions
minus return flows) to mainstem Klamath River flows in the spring is 1,000 cfs, the proposed
action is likely to increase water temperature in the mainstem Klamath River between IGD and
the Scott River by up to approximately 0.5 °C during the spring. Below the Scott River mouth,
the proposed action’s effects on water temperature in the spring are likely insignificant because
cold water accretions and meteorological conditions have a pronounced effect on water
temperatures in the mainstem Klamath River. In the summer and early fall, any decreases in
IGD flows are likely to reduce water temperature in the mainstem Klamath River because
reservoir water behind IGD is warmer than mainstem Klamath River water.
Nutrients and Dissolved Oxygen
Temperature is a primary influence on the ability of water to hold oxygen, with cool water able
to hold more dissolved oxygen than warm water. The proposed action’s warming effect on water
temperatures and longer transit times increases the probability that dissolved oxygen
concentrations will decrease in the mainstem Klamath River downstream of IGD. In addition,
the proposed action also indirectly affects pH and dissolved oxygen through its interactions with
periphyton, algae that grow attached to the riverbed.
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