Assessment of water quality in the rivers of northern European Russia by using oxygen demand indices

Analysis of the probability curves of multiyear organic content data and water colour indices of the rivers located in the northern part of European Russia (the Northern Dvina, Pechora, Onega, and Mezen) allowed revealing seasonal patterns of hydrochemical indices. Water quality for different seasons was assessed. Regional estimates of hydrochemical indices and water quality were obtained. Relations between oxygen demand indices, water colour indices, and water content of those rivers were considered.