EVALUATION OF THE WATER-QUALITY OF FUTURE TRIBUTARIES TO THE PLANNED DOBCZYCE RESERVOIR (POLAND) USING MACROINVERTEBRATES

The bottom fauna of 5 tributaries of the planned Dobczyce reservoir and the River Raba below the dam was investigated in the preimpoundment period (1983-84). The abundance of macrofauna varied between 46 taxa (Wolnica stream) and 66 taxa (Brzezowka stream). Each station showed individual taxa composition except for the RABA-u and RABA-d (84% similarity). On the basis of 7 different biological indices the stations were divided into 3 categories: unpolluted (Brzezowka), slightly polluted (Bulinka, Trzemesnia and both Raba stations), and moderately polluted (Wolnica). Most sensitive to chemical pollution was the BIOTIC-index. The combination of environmental variables was used to predict biological indices. The most significant relationship (P < 0.01, R2 = 0.71) was found between the BIOTIC-index and physico-chemical factors. Some problems in the application of indices (sampling, indicator organisms and interpretation of the results) are discussed and local adaptations of methods used are recommended.