Biological Opinions - Bureau of Reclamation

The proposed action results in agricultural tailwater discharges at the Lost River Diversion Canal
and the Klamath Straits Drain. These discharges occur in the Link River upstream of Keno Dam,
and contribute to impaired water quality conditions in the mainstem Klamath River downstream
of IGD (Figure 7.5). While the Klamath Project is a net sink for nutrient load on an annual basis
(Rykbost and Charlton 2001, Danosky and Kaffka 2002, ODEQ 2010), these agricultural
discharges generally increase the nutrient concentration of the Keno Impoundment reach in the
summer and fall (ODEQ 2010, Reclamation 2012). Nutrient concentrations decline with
distance downstream due to dilution by tributaries and interception and retention within Copco
and Iron Gate Reservoirs; however, enough nutrients pass through the reservoirs to still support
abundant growth of periphyton in the mainstem Klamath River below IGD (USDOI and CDFW
2013). Total phosphorus will slightly increase downstream of IGD because of the increased
nutrient concentrations released from the Klamath Straights Drain or the Lost River Diversion
Channel in the summer and fall (Asarian 2013).
The seasonal (summer/fall) release of nutrients out of Iron Gate Reservoir stimulates periphyton
growth in the mainstem Klamath River (USDOI and CDFW 2013). The NRC (2004) stated that
stimulation of any kind of plant growth can affect dissolved oxygen concentration. However,
because nutrient concentration is only one factor influencing periphyton growth, the small
increase in nutrients may not necessarily increase periphyton growth. Other factors influencing
periphyton growth include light, water depth, and flow velocity. In addition, many reaches of
the Klamath River currently have high nutrient concentrations that suggest neither phosphorus
nor nitrogen is likely limiting periphyton growth. Thus, an increase in nutrient concentration
would not necessarily result in worse dissolved oxygen and pH conditions.
While the proposed action’s increase in nutrients in the mainstem Klamath River between IGD
(RM 190) and Seiad Valley (RM 129) is not likely to have a direct influence on periphyton
growth, the proposed action’s reduction of mainstem flows has a larger effect on periphyton and
its influence on dissolved oxygen concentration. Several mechanisms are responsible for flow
effects on periphyton biomass. Some of these include the relationship between flow and water
temperature, water depth, and water velocity. When low flows lead to warmer water
temperature, periphyton growth likely increases (Biggs 2000). High flows increase water depth,
which likely reduce light penetration in the river. Conversely, low flows generally decrease
water depth, which increases periphyton photosynthesis. Low water depth also disproportionally
amplifies the relative water quality effects of periphyton (i.e., diel cycles of dissolved oxygen
would be magnified) because the ratio between the cross-sectional area and channel width
decreases (i.e., mean depth decreases). In other words, the inundated periphyton biomass 6 would
have greater water quality effect on the reduced water column (Figure 11.20, Asarian and Kann
2013).
6 Periphyton are attached to the riverbed and exert their influence on the water column chemistry
by impacting diel cycles of photosynthesis and respiration in the overlying water column.
Although periphyton would also decrease as the wetted channel area declines, they would
decrease at a lower rate relative to water volume changes because the ratio of area:volume
increases with decreased flow.
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