A simple method to estimate lake phosphorus concentrations resulting from natural, background, loadings

The relation of mean total phosphorus concentrations to morphoedaphic index (calculated as the ratio between the mean depth and the alkalinity or the conductivity) has been examined for a large, diverse, widely distributed group of lakes.A highly significant correlation was found in lakes practically not affected by anthropogenic input of phosphorus. As a consequence the phosphorus concentration in a lake resulting from natural, background, loading could be calculated on the basis of the morphoedaphic index. The evaluation of natural phosphorus concentration allows the prediction of the maximum extent to which actual phosphorus concentrations could be reduced in culturally eutrophied lakes by eliminating the anthropogenic inputs and to calculate “permissible” loadings necessary to achieve natural trophic conditions that will not necessarily correspond to oligotrophy.