The article discusses the results of hydrochemical study of different types of lakes
in the Raifa cluster of the Volzhsko-Kamsky Nature Reserve and its buffer zone (Republic of Tatarstan), carried out in 2021–2023. The spatial variability of the total mineralization of the water bodies in the basins of the Sumka and Ser-Bulak Rivers is presented. The article gives a comparative description of the gas regime, the content of organic substances (in terms of BOD5 and COD) and nutrients in open and closed lakes, as well as the calculated coefficients of exceeding the maximum permissible concentrations for all indicators. The degree of the lakes pollution was assessed on the basis of the specific combinatorial index of water pollution.