An analysis of the efficiency of the surface water treatment systems of the Dnipro reservoirs when their quality is changed to ensure the normative indicators of the quality of drinking water were carried out. The study of the effectiveness of traditional water treatment technologies was carried out by analyzing the results of laboratory studies of source and drinking water at the Dnipro water treatment plant with water intake from the Kremenchuk Reservoir (data from the Svitlovodsk Water and Sewage Services (SWS) of the Regional Municipal Production Enterprise (RMPE) of the Dnipro-Kirovograd), establishing correlations of quality indicators and assessing the state of water resources by the requirements of water legislation. The treatment plants of the Dnipro water supply station are not designed to treat water with a high content of biogenic substances during active phytoplankton vegetation, and under such conditions, increased doses of preliminary chlorination are used. As a result, water is polluted with residual chlorine and organochlorine. An increase in the dose of aluminum-containing coagulants in the corresponding period leads to an increase in the aluminum content in drinking water to the limit of the normative value (0,5 mg/dm3). According to the results of research in drinking water, turbidity was found to be 1,4 higher and permanganate oxidizability 1,3 higher than the standard content; excesses of color, iron, and residual chlorine content were found only sporadically and were on average within the upper limits of normative values. Correlation analysis (Pearson and Spearman correlations methods) of the influence of temperature on the following hydrometric, chemical, and physical factors was carried out: changes in turbidity, color, and changes in the concentration of total iron and ammonia. The analysis confirmed the visual connection of oxygen with temperature and water level and the influence of factors on oxygen concentration. The practical aspects of phytoplankton extraction during water intake from Dnipro reservoirs and water treatment at stations have gained further scientific justification.