The use of the Biological Diatom Index (BDI) for the assessment of water quality in the Pilica River, Poland

The main aim of this study was to assess the usefulness of the Biological Diatom Index (BDI) (Lenoir & Coste 1996) for the estimation of water quality in the central section of the Pilica River, located in central Poland in Łódź province. The BDI has never been used before to monitor Polish surface waters. An analysis of the correlations between the values of the BDI and selected physico-chemical parameters was performed, as was an assessment of water quality using the BDI. On the basis of value ranges proposed by Descy and Ector (1996), a good ecological status in the Pilica River was obtained, but this did not correspond with the results achieved from the physico-chemical analysis. This study proposes new value ranges for the BDI. With these new values, the ecological state of the Pilica River changed from good to moderate, which corresponded with the physico-chemical analysis of the water. The new, proposed value ranges for the BDI assess more precisely the quality of water in lowland Polish rivers.