Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Endangered Suckers: Review of Proposed Action
Wood et al. 2006, Kuwabara et al. 2007, Morace 2007), the effect of lake level on
algal biomass is of particular importance. Upon analysis of existing data, NRC
(2002) found no relationship between UKL level and AFA density (represented
by chlorophyll concentration) and the idea of reducing algal density by
phosphorous dilution with higher lake levels is “not consistent with the irregular
relationship between chlorophyll and lake level.” As depicted by Figure 2-21
from NRC (2002), there is no apparent association between lake level and the
intensity of AFA blooms.
Also, NRC (2002) was unable to identify a quantifiable relationship between
UKL depth and extremes of DO or pH. In fact, the most extreme pH conditions
recorded for UKL during the 10-year period from 1990-2000 occurred in 1995
and 1996, which were intermediate water depth years, and not during 1992 and
1994 when water levels were the lowest (NRC 2002). The 10-year period that
NRC (2002) analyzed from 1990-2000 were within the historical range of
operations for UKL. The years of 1995, 1996, and 1997 (Figure 2-21), where
extensive fish die-off events were observed, were intermediate lake level years.
Further, 1991 was a low lake level year and yet was also a year of good sucker
recruitment (NRC 2002).
USGS has conducted extensive analyses of existing water quality data from UKL.
Wood et al. (1996) and USGS, concluded that there was no evidence for a relation
between any of the water quality variables considered (chlorophyll, DO, pH, and
total phosphorus) and lake depth on the basis of seasonal distribution of data or a
summary seasonal statistic. The analysis found that low DO, high pH, high
phosphorus concentrations, and heavy blooms of AFA were observed each year
regardless of lake depth. The USGS repeated this analysis with a 17-year dataset
(1990-2006) and the inclusion of eleven more years of data did not demonstrate a
discernable relationship between lake depth and water quality (Morace 2007).
Wood et al. (1996) did find that lower lake levels coincided with an earlier onset
of the AFA bloom; however, these findings were not supported by Morace (2007)
with the analysis of the more robust 17-year dataset. Both Wood et al. (1996) and
Morace (2007) found a relationship between spring temperatures and the timing
of the onset of the AFA bloom. The onset of the AFA bloom was delayed when
spring air temperatures were cooler (Wood et al. 1996, Morace 2007). These
analyses suggest that climactic conditions may have a greater influence on UKL
water quality than lake level and the other variables considered. This is not to say
that water depth has no effect on water quality, but that existing data and analyses
have not shown a discernable relationship between UKL elevation and water
quality over the range of depths that UKL has been operated at during the period
from 1990-2006.
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