Upper Klamath Lake Basin Nutrient-Loading Study-Assessment of Historic of Flows in the Williamson and Sprague Rivers

The Williamson River Basin, located in south-central Oregon, has a drainage
area of approximately 3,000 square miles. The Sprague River, which flows into
the Williamson River Basin, has a drainage area of 1,580 square miles.
Together, the Williamson and Sprague Rivers supply about one-half of the inflow
to Upper Klamath Lake. Various statistical techniques, which included trend
tests, double-mass curves, and two-sample tests, were used to detect
significant changes in the precipitation-runoff relation for the Williamson and
Sprague River Basins. Flows from these two rivers were compared with the
precipitation and air temperature records collected at Klamath Falls to assess
the effect of climate on flow variations.

Most of the double-mass curves showed a major break in the slope of the
curve
occurring around 1950 and a smaller one near 1990. For the years 1930-50 and
1990-96, February through May flows were relatively lower in the Williamson
River than in rivers in nearby basins, by an average of 25,000 acre-feet per
year and 36,000 acre-feet per year, respectively, for the 4-month period. From
1950 through 1963, flows were generally higher in the Williamson River compared
with the nearby rivers by an average of 38,000 acre-feet for the 4 months. In
July through September of 1945-51, 1970-76, and 1992-96, flows were lower in
the Williamson River than in the comparison rivers by an average of about 6,000
acre-feet for the 3-month period. Two-sample statistical tests of the annual
flow data sets for the Williamson and Sprague Rivers showed significant
increase in the estimated population mean for the period 1951-96 compared to
the estimated population mean for the period 1922-50. However, climate data,
which included annual precipitation data from Klamath Falls, Crater Lake, and
Medford, and annual air temperature data from Klamath Falls, all showed no
significant difference between the two periods. During the past century,
various human land-use activities, such as irrigation, grazing, drainage, and
timber harvesting, may have had some impact on the hydrology within the
Williamson River Basin. However, relating specific land-use activities to
changes in flow is impossible to assess owing to the size and geologic
complexity of the basin and to the paucity of historical land- and water-use
data for local areas.

The area of study was Upper Klamath Lake Basin, Oregon, Williamson and Sprague
Rivers.

Statistical techniques were used to analyze the Williamson and Sprague River
streamflow data. Trend analysis was used to detect an increase or decrease in
streamflow for the period of record as measured near the mouth of each river.
Double-mass curve analysis was used to detect possible changes in runoff
patterns during the period of record that could indicate human influences in
the basins. Long-term precipitation and air temperature data collected near
the basins were used in these analyses to remove the influence of climate from
the runoff data.

The information for this metadata was taken from the Online Publications of the
Oregon District at http://oregon.usgs.gov/pubs_dir/online_list.html .