The paper presents results of analyses of selected physico-chemical and biological parameters in four rivers (the Buczynka, the Kosówka, the Ugoszcz, the Osownica) situated in the Nadbużański Landscape Park. Chemical assessment of the rivers was performed in accordance with the water classification valid in Poland while their biological assessment was carried out basing on the taxonomic composition of macroinvertebrates and in accordance with the Belgium Biotic Index (BBI). The chemical parameter decisive for the final classification of water was the concentration of phosphates. Particularly high substandard values of these ions were recorded in the Buczynka and the Kosówka rivers in places located below the outlets of sewage treatment plants. These stations also turned out to be deficient in macroinvertebrates sensitive to water pollution (plecopteran, ephemeropteran, caddis-fly larvae). According to the 5 class scale of water quality the Ugoszcz and the Osownica carry the 2^nd class water in the majority of analysed stations, while the Buczynka and the Kosówka carry the 3^rd class water. These tributaries bring to the Bug river moderately or slightly polluted waters. The results indicate that investigated rivers are higher classified according to biological indices than to chemical ones.

3-17