A simple model for predicting the date of fall turnover in thermally stratified lakes

The date of fall turnover c.an be predicted from average midsummer hypolimnetic temperature in acidic and non-acidic lakes in central Ontario. The prediction of fall turnover date is improved by inclusion of two further independent variables, mean depth (z) and adjusted latitude (for altitude), in a global data set (ranges of z, 1.1–86 m; adjusted latitude, 38°–65°). The models explain 67–80% of the variance of fall turnover date and are potentially useful in the design of monitoring programs and for predicting impacts of anthropogenic activities that influence lake thermal budgets, e.g. diversion for cooling waters or damming of cold inflows.