Changes in Water Quality in the Modonkul River Assessed by Combinatory Pollution Index

Water quality in the Modonkul’ River, flowing in a territory with mining industry, is considered. The analyzed data characterize the period 2019–2021. The assessment of pollution or the parameterization of water quality were carried out using the universal combinatory index of water pollution. In the upper reaches of the Modonkyl’ River, the water chemistry is of hydrocarbonate calcium type. In the zone of mixing of river and mine waters, the water chemistry changes to sulfate, mostly, sodium-calcium-magnesium type. The general regularity in the behavior of microelements in the Modonkul’ R. water is an increase in their concentration at an increase in TDS. Downstream the river, the concentrations of heavy metals increase: Cu, Zn, Pb by 1.1–1.4 times; Mn, Co, As by 6.6–11 times; and Cd, by 8 times. In the upper reaches of the river, its water quality was classified as weakly polluted, 2nd class. Further downstream, the water is classified as dirty, 4th class with a decrease in the subclass from a to b.