COMPARISON OF METHODS FOR DETERMINATION OF TOTAL SOLUTES IN FLOWING WATERS

In the Saskatchewan River Basin, Canada (area: 365 00O km2), we compared methods of measuring total solutes concentrations, and assessed cross-channel and diurnal variation within sites, using data collected over 25 years at numerous sites throughout the basin. Regression analysis indicated that total solutes concentrations measured as the sum of major inorganic ions (TS(c)) could be reliably converted to concentrations measured by filtration (FR) or evaporation by FR = 1.055(TS(c)). CoeffiCients of variation (CV) for multiple total solutes samples taken within 1 day at four sites were usually less than 5% and always less than 10%, suggesting that the daily mean concentration may be reliably estimated from a single sampling time. At 20 sites, C V of total solutes samples taken at points across the river channel were always less than 10%, and were less than 5% in 77% of samples. Cross-channel variation was unaffected by solutes concentration (86-317 mg l-1), discharge, time of year, or type of watercourse (prairie river or mountain stream). Statistical comparisons indicate that cross-channel variation in total solutes concentrations is unlikely to be significant except where tributary inflows have not yet mixed with flow in the main channel.