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

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 oregon.usgs.gov/pubs_dir/online_list.html .