The purpose of the work is to identify the current state and long-term changes in the hydrochemistry of the Pavlovsky reservoir, which allow further development of programs for its environmental rehabilitation. An analysis of studies of the current state and long-term changes in hydrochemistry (the content of chemical elements in water) of the Pavlovsky reservoir for 10 chemical indicators in 7 sites is presented. The factors that form and change the hydrochemistry of the Pavlovsky reservoir are studied. It was revealed that throughout the reservoir, from its beginning to the upper stream, the content of Sr2+, Mn2+ and petroleum products in the water decreases; increase – Zn2+, Hg2+, phenols and organic substances; are evenly distributed – Fettl (Fe2+ + Fe3+), Pttl (according to PO4 3-), Cu2+. A long-term trend of reducing the content of chemical elements in water is noted for Fe, Mn2+, petroleum products, phenols, COD; upward trend – for Rttl, Cu2+, Zn2+, phenols. The relationship between the average annual content of chemical elements in water and the values of average annual imflows has been established. Based on the results obtained, priority ways to improve the hydrochemistry of the Pavlovsky reservoir have been identified.