Limnological studies of the lakes and streams of the upper Qu'Appelle River System, Saskatchewan, Canada

Abstract

Physical aspects including geography, geology, climate, soils, vegetation and lake morphometry of the upper Qu'Appelle River basin have been summarized. The importance of multiple use of this area has been stressed. The lakes were studied during the 1959–1969 period. Only Katepwa Lake showed temperature stratification for any length of time. Ice cover persisted for about five months each year. Buffalo Pound Lake had the lowest mean Secchi disc transparency (0.9 m) while Katepwa Lake had the highest (2.1 m). Light transmissibility tended to be lowest during May and September when wind velocities were highest. The 1 % level of light extinction was usually between 1 and 3 meters depth. The yellow portion of the spectrum penetrated the furthest. Buffalo Pound Lake was the least saline (600–700 mg/l TDS) while Last Mountain Lake was most saline (2000–2400 mg/l TDS). Input from Lake Diefenbaker and heavy spring runoffs effected major decreases in all lakes by May 1969. All lakes except Last Mountain were considerably more saline than during the 1937–1941 period. Variations in anions and cations within and between lakes vary with the total dissolved solids. As salinity increases magnesium, sulphate and chloride increase faster proportionally than other ions. The order of concentration of major cations is Na > Mg > Ca > K while the major anions' order of concentration is SO4 > CO3.HCO3 > Cl. Soluble phosphate levels tend to be lowest in Buffalo Pound Lake. Levels increased sharply in Pasqua Lake below sewage outfalls from Moose jaw and Regina. Subsequently levels decreased in each successive downstream lake. Concentrations increased during the period of study. It was estimated that 594 metric tons of orthophosphate were contributed in domestic sewage in 1966. In addition land drainage contributes considerable amounts of phosphate during spring runoff. Nitrogen-bearing compounds vary in similar patterns as soluble phosphate but with smaller fluctuations. Domestic sewage and land drainage contribute significant amounts but of greater importance may be in situ biological fixation. All lakes were basic with usual pH of 8.4–9.0. From a chemical point of view these lakes are distinctly eutrophic.