Trace Elements in the Oldman River of Southern Alberta

Abstract

Abstract The Oldman River in southern Alberta is a mainstem river used extensively by aquatic life, for community drinking water, irrigation water, recreation, and livestock watering. Therefore, maintaining the water quality of this important river is critical for watershed health. We collected water samples weekly from three locations on the middle reach of the Oldman River from 2004 to 2006. The locations were: Lethbridge Municipal Water Treatment plant (MWTP) (Site 1), Fort MacLeod MWTP (Site 2), and a river bank sampling location downstream of the latter site (Site 3). Water samples were analyzed for background physical and chemical variables, and for selected trace elements (Al, Fe, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Zn). The aquatic life, community, irrigation, and livestock water quality guidelines at the three sites were most frequently exceeded by Cu (27-48%), Al (3.3-57%), Co (18-26%), and Al (2.3%), respectively. Concentrations of certain trace elements were highest in the spring or during years of above average precipitation, and were likely associated with increased loads of suspended sediments during high flow conditions. Turbidity, water temperature, electrical conductivity, river level, and precipitation generally had a positive effect, and pH had a negative effect on certain trace element concentrations.