Based on bacteriological laboratory data, an analysis and assessment of the intra-annual variability of bacteriological pollution were carried out. As a result of a comparative sanitary and microbiological analysis of the degree of pollution, the classification of small rivers was carried out, which indicates the level of anthropogenic loadduring the year. Intra-annual variability was revealed, both in terms of the identified pollutants and the levels of their excess, and also the priority intra-annual river pollutants were determined. General conclusions are formulated.