ASSESSING THE POTENTIAL EXTENT OF DAMAGE TO INLAND LAKES IN EASTERN CANADA DUE TO ACIDIC DEPOSITION .1. DEVELOPMENT AND EVALUATION OF A SIMPLE SITE MODEL

This paper presents a model that uses measurements of current lake chemistry and assumptions about the processes governing acidification, to first estimate original (i.e. preacidification) lake chemistry and then predict the eventual chemistry expected given a specified level of acidic sulphate deposition. When applied on a regional scale the model predicts the expected eventual distributions of alkalinity and pH. Application of the model is illustrated for a watershed in north-central Ontario. Model-based estimates of current alkalinity are very similar to observed alkalinities. The predicted eventual alkalinity distributions, given current levels of deposition, indicate a trend towards recovery. A sensitivity analysis of the model indicates that its outputs are highly sensitive to estimates of preacidification lake sulphate levels, and less so to assumptions about the catchment's ability to neutralize incoming acidity. -from Authors