The paper presents the results of observations of the spatial variability of the chemical composition of the river Modonkul. According to these observations, the chemical composition of the water changes from bicarbonate calcium-magnesium in the upper part of the river through sulfate-calcium-sodium (and other transitional differences to sulfate-calcium-magnesium type) in the river's mouth. Redistribution of dissolved and suspended forms of migration of heavy metals occurs in the alkaline environment in river Modonkul. The data of the content of rare earth elements in water river are obtained.