The formation and distribution of river flow characteristics in the Don basin have been catholically analyzed, depending on the present-day climatic conditions in the central European Russia. The recent global warming is shown to have resulted in a change in the river flow formation conditions and water resources, as well as in a substantial transformation of the river water regime in the basin. The river water and groundwater chemistry in the basin in 1990–2015 has been considered at the main observation points. The dynamics of river water quality pollution level during the long period is presented. Water pollution characteristics, which make it possible to identify the water quality class and pollution level, have been used to give a generalized estimate of the water quality in the chosen river areas.