A macro-invertebrate based new biotic index to monitor river water quality.

A macro-invertebrate based new biotic index is proposed to evaluate water quality in freshwater rivers. The new index is based on the data gathered and analysed from 21 sampling sites of eight rivers/streams of Sikkim in Eastern Himalaya. The sampling sites were chosen in such a manner to include the river stretches with disturbed, moderately disturbed and undisturbed catchment areas. The proposed index was calibrated against water quality index (WQI) of National Sanitation Foundation (NSF), USA and various other known biotic indices. The proposed index gives better results of the water quality of rivers compared to the existing abiotic and biotic indices, because: (i) it takes into account the abundance of taxa and reflects even the minor changes in abundance and community structure of the river ecosystem, (ii) it is flexible and gives freedom to select any pollution sensitivity score system based on family, generic or specific levels and (iii) it is universally applicable and is not affected by the geographic location of a river. [ABSTRACT FROM AUTHOR]