Trends in long-term water quality changes in Ivan’kovo and Uglich reservoirs

Abstract

A comparative analysis of water quality indicators in the upper and lower parts of the Ivan’kovo and Uglich Reservoirs was carried out based on the analysis of long-term monitoring datasets on water quality condition in reservoirs. The observations were performed at the gauging stations of the State Observation Network and Mosvodokanal in the period from the mid-1980s to 2019 and 2004 accordingly. Over a long-term period, all studied hydrochemical indicators except for Zn and SO4 tend to decrease closer to the dam both in the Ivan’kovo and Uglich Reservoirs. Two periods with sufficiently different average values of considered parameters and their dynamics were distinguished for the Uglich Reservoir according to statistical analysis. A high level of pollution in the Uglich Reservoir is mainly associated with heavy metals (Cu, Zn, Fe), phenols and oil products and is typical for both the upper and lower parts of the reservoir. Such pattern is inherent to both heterogeneous periods (1985-2000 and 2001-2019) identified for the Uglich Reservoir. The main trends of long-term and seasonal variability in water quality of the Ivan’kovo and Uglich Reservoirs have been identified using the water pollution index.