A method for predicting the lake trophic status relying on wintertime monitoring data was developed. The technique is based on A. G. Volokhonskii’s approach, according to which the values of the minimum energy costs calculated for the virtual model of the process of involving mineral nutrients in phytoplankton cells are universal criteria of these nutrients’ availability to phytoplankton. Statistically significant one-parameter linear dependence between the average annual concentration of total phosphorus (Pt) and the values of minimum energy costs (Ep), which characterize mineral phosphorus levels in February, was detected. A classification of the trophic status of lakes ofKazakhstan depending on the values of the minimum energy costs of mineral phosphorus in February was developed.