Influence of Atmospheric Deposition on Lake Mass Balances in the Turkey Lakes Watershed, Central Ontario

Abstract

Ion mass budgets were measured for 2 water yr (June–May, 1981–83) for a high and a low elevation lake and their associated catchments. The lakes are located in the Turkey Lakes Watershed (TLW) in central Ontario, Canada, which is an undeveloped basin located on the Canadian Shield, 50 km north of Sault Ste. Marie. The ionic budgets of the lakes show that atmospheric deposition directly to the lakes’ surfaces is the principal input pathway for H+ and NH4, whereas basic cations, SO4, NO3, and probably alkalinity are supplied primarily by inflow from the surrounding terrestrial basin and/or upstream lake. The lakes strongly retain H+ (i.e. output 00AB; input), weakly retain the N species, and are in balance (i.e. output = input) for other ions except Ca and alkalinity which show an excess output compared to measured + estimated inputs. We hypothesize that an input of groundwater and/or seepage accounts for most of the Ca and alkalinity imbalance although the existence of within-lake alkalinity generation is probable also.