Biological Opinions - Bureau of Reclamation

1991 through 2012 -2.9% 1.00 3.8% 1.00 10.0% 0.91
2001 through 2012 62.4% 0.37 29.8% 0.37 22.1% 0.19
1 p-value indicates the probability that the change in inflow is caused by chance rather than a trend.
Shading indicates the values considered statistically significant at an alpha of 0.10
The most conspicuous July through September trend (Table 7.7), is the statistically valid decline
in flows for the almost all periods except those from 1991 through 2012. The most probable
explanation for July through September declines during years when flows are increasing in other
seasons is irrigation withdrawals. No statistically significant trend is present in the 1991 and
2001 through 2012 periods, except for an increasing trend in the Williamson River in the past
decade.
Table 7.7 Percent change in July through September median monthly flows in the Sprague and Williamson
Rivers and net inflow to UKL, 1918 through 2012.
Mann-Kendall Trend Test Results: July through September
Sprague River Williamson River Upper Klamath Lake
Time Period % change p-value 1 % change p-value 1 % change p-value 1
1918 or 1921 through
2012 -24.3% 0.01 -17.8%