Biological Opinions - Bureau of Reclamation

ammonia that is lethal to 50 percent of test individuals) values for un-ionized ammonia varied
from 0.48–1.29 mg/L for 96 hour exposures for larval and juvenile suckers. Meyer and Hansen
(2002) concluded that the LC 50 for indefinite exposure of LRS early life stages to un-ionized
ammonia is approximately 0.5 mg/L.
B. Martin (USGS, pers. comm., 2012) reviewed water quality data for UKL to determine water
quality associated risks. Data from approximately 3,800 samples were analyzed for DO, pH,
temperature, and total ammonia-nitrogen using data collected by the Klamath tribes and USGS
since 1991. The results showed that the total ammonia-nitrogen concentrations were at threshold
values for the suckers in most years, suggesting this compound is a noteworthy threat to the LRS
and the SNS in UKL. DO concentrations rarely exceeded the LC 50 value, but about 10 percent
were about at the 4.0 mg/L stress threshold. pH values also rarely exceeded the LC 50 value of
10.3, but about 15 percent exceeded the high stress level of pH 9.75.
Keno Reservoir is currently listed as impaired year-round for ammonia toxicity under section
303(d) of the Clean Water Act (ODEQ 2010). In the 2010 TMDL for the Oregon portion of the
Klamath River that includes the Keno Reservoir, ODEQ (2010) described ammonia
concentrations, which peak at Miller Island (RM 245) in July and August. Total ammonia
nitrogen concentrations in the Keno Reservoir frequently exceed Oregon’s chronic criteria from
June to September, and can exceed the acute criteria in both June and July (ODEQ 2010). These
degraded conditions can occur throughout much of the 20 mile long reservoir, with better
conditions only in the uppermost and lowermost reaches. Fish die-offs in the Keno Reservoir
occur in most summers (USFWS 2008).
7.10.1.4 Nutrients
Primary plant nutrients, including nitrogen and phosphorus, are affected by the geology of the
surrounding watershed of the Klamath River, upland productivity and land uses, and a number of
physical processes affecting aquatic productivity within reservoir and riverine reaches. Nitrogen
arriving in UKL has been attributed to upland soil erosion, runoff, and irrigation return flows
from agriculture, as well as in situ nitrogen fixation by cyanobacteria, especially AFA (ODEQ
2002). Although the relatively high levels of phosphorus present in Upper Klamath Basin
volcanic rocks and soils have been identified as a major contributing factor to phosphorus
loading to the lake (ODEQ 2002), land use activities in the Upper Klamath Basin have also been
linked to increased nutrient loading (Snyder and Morace 1997, Kann and Walker 1999, Bradbury
et al. 2004, Colman et al. 2004, Eilers et al. 2004), subsequent changes in trophic status, and
associated degradation of water quality. Extensive monitoring and research conducted for
development of the UKL TMDLs (ODEQ 2002) show that the lake is a major source of nitrogen
and phosphorus loading to the Klamath River. Nutrient and organic matter inputs from the Lost
River Basin via Klamath Straits Drain and the Lost River Diversion Channel are also an
important source of nutrients to the Upper Klamath River (Figure 7.5; Sullivan et al. 2009,
ODEQ 2010).
The operations of Keno Dam likely reduce nutrient cycling that would improve water quality in
Keno Reservoir. The dam and its impoundment affect water quality primarily by increasing
surface area, hydraulic retention time, and solar exposure (FERC 2007). The longer residence
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