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Trends in selected water-quality characteristics, Flathead River at Flathead, British Columbia, and at Columbia Falls, Montana, water years, 1975-86

Water-Resources Investigations Report 89-4054

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Abstract

Data for selected water quality variables were evaluated for trends at two sampling stations--Flathead River at Flathead, British Columbia (Flathead station) and Flathead River at Columbia Falls, Montana (Columbia Falls station). The results were compared between stations. The analyses included data from water years 1975-86 at the Flathead station and water years 1979-86 at the Columbia Falls station. The seasonal Kendall test was applied to adjusted concentrations for variables related to discharge and to unadjusted concentrations for the remaining variables. Slope estimates were made for variables with significant trends unless data were reported as less than the detection limit. At the Flathead station, concentrations of dissolved solids, calcium, magnesium, sodium, dissolved nitrite plus nitrate nitrogen, ammonia nitrogen (total and dissolved), total organic nitrogen, and total phosphorus increased during the study period. Concentrations of total nitrite plus nitrate nitrogen and dissolved iron decreased during the same period. At the Columbia Falls station, concentrations increased for calcium and magnesium and decreased for sulfate and dissolved phosphorus. No trends were detected for 10 other variables tested at each station. Data for the Flathead station were reanalyzed for water years 1979-86. Trends in the data increased for magnesium and dissolved nitrite plus nitrate nitrogen and decreased for dissolved iron. Magnesium was the only variable that displayed a trend (increasing) at both stations. The increasing trends that were detected probably will not adversely affect the water quality of the Flathead River in the near future. (USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Trends in selected water-quality characteristics, Flathead River at Flathead, British Columbia, and at Columbia Falls, Montana, water years, 1975-86
Series title:
Water-Resources Investigations Report
Series number:
89-4054
Edition:
-
Year Published:
1989
Language:
ENGLISH
Publisher:
Dept. of the Interior, U.S. Geological Survey ; Books and Open-File Reports Section [distributor],
Description:
iii, 14 p. :ill. ;28 cm.