SEASONAL VARIATIONS IN WATER QUALITY OF THE UPPER OLDMAN RIVER

Abstract

Water samples were collected monthly from the upper Oldman River during 1982. In that year, precipitation at the nearest weather station was 7% below the 81-year average of 407 mm and could be considered a normal precipitation year. Surface runoff from annual precipitation in the watershed accounts for the dominant portion of the water that fills the Oldman River, which is highly dependent on winter snowpack and spring and fall rains. Twenty-two water quality parameters were determined. The parameters reflected seasonal fluctuations and provided baseline reference data for the upper Oldman River. Soluble salts were highest in the winter-spring period, and dropped during the summer period. Calcium and magnesium increased during the fall-winter period. Total water hardness was highest in the fall-winter period and specific conductance was highest in the winter-spring period. Total, soluble, and particulate phosphates were highest during the summer period owing to the heavy rains in June and July. Nitrates were highest during the winter-spring period. Total solids, total dissolved solids, and silt were low throughout the year because of the heavily forested, undisturbed nature of the upper Oldman River watershed.