The paper presents the research results on the content and spatial dynamics of biogenic elements (ammonium ions, nitrite ions, nitrate ions, mineral phosphorous) in the water of the Bâc river. The aim of the research was to determine the water quality of the Bâc river, in order to highlight the extent of the impact of anthropic factors on the river and to reveal the impact of the Bâc river on the state of the Dniester river. The water of the Bâc river, downstream of Calarasi, Straseni and Chisinau, is highly polluted with ammonium, nitrites, mineral phosphorus, which corresponded to the IV-V class of water quality - polluted and heavily polluted. The results of the research confirm the high degree of pollution with biogenic elements causing the changes of water quality in the Dniester river.