The Central Pollution Control Board (CPCB) during the development and testing of bio-monitoring methodology in collaboration with Dutch experts has established that the inclusion of bio-monitoring parameters, apart from physico-chemical parameters, in water quality monitoring network will enhance the quality evaluation in a cost-effective manner. Among all the biotic components of river, the benthic macro-invertebrates have been considered as the most suitable biological parameter for water quality evaluation due to the following facts:

• The benthic macro-invertebrates are visible to unaided eye and are retained on a seive with a mesh size of 0.6 mm diameter
• Macro-invertebrates are inhabiting the different substratum of rivers, streams, lakes and other water bodies
• Water bodies having different quality, support diverse macro-invertebrate communities
• Their taxonomy is well developed
• Demonstrate an integrated effect of pollution
• Provide good experimental possibilities
• Useful in assessing the impact of municipal, industrial and agricultural wastes
• Community response is sensitive to organic loading, thermal impacts, substrate alterations and toxic pollution.