A Revised Classification of Lakes Based on Mixing

Deficiencies in the Hutchinson–Löffler classification of lakes based on mixing are reviewed and organized under the following headings: (1) exclusion of shallow lakes, (2) unsatisfactory relationship between meromixis and the six basic lake types, (3) excessively complex treatment of tropical lakes, and (4) difficulties in classification of cold lakes due to the 4 °C boundary on cold monomixis. A revision remedies these deficiencies with minimal changes in terminology and conceptual foundation of the original classification. The revision incorporates the following features: (1) the meromixis/holomixis dichotomy is combined with the six lake types based on seasonal mixing in such a way that the two systems are hierarchical and universal; meromictic lakes are assigned to a seasonal type on the basis of the behavior of the upper water column, (2) oligomixis is eliminated, (3) shallow lakes are brought under the classification by definition of four polymictic types based on ice cover and frequency of mixing. Dependence of the eight mixing types of the revised classification on latitude, elevation, and depth is estimated from existing data, and examples are given of each type.