A Guide to Bioassessment of Stream Health: A research based in BHUTAN.

A rapid bioassessment methodology was employed for macroinvertebrate sample collection from five different streams in south-west Bhutan. These streams corresponded to different levels of disturbance. All streams were subjected to seasonal high stream flow as a major predictable disturbance during monsoon. Sampling was performed on monthly basis for the period of 10 months between monsoons to account for both spatial and temporal (seasonal) variation. Measured physicochemical parameters showed some variations among the investigated streams. Investigated streams showed a diverse range of macroinvertebrates, but the community composition varied both spatially and temporally in different streams. An assessment of HKH score variability was performed relative to field sampling efforts associated with rapid bioassessment. The index was not strongly influenced by variation in sample size and field sorting techniques, and thus usable macroinvertebrate based information could be provided with minimum costs and time involvement. However, there was considerable variation among individual samplers in the index scores derived from single samples, suggesting experience of samplers is important.