Tehri hydroelectric project of 2,400 MW capacity, the Asia's highest dam constructed on the Bhagirathi river in Uttarakhand is one of the most debatable dams of the country. The fluvial system of Bhagirathi and Bhilagana has been converted into a huge lentic water reservoir. Therefore, the information on periphytonic diversity before impoundment is very important.

Aquatic macroinvertebrate diversity in the Bhagirathi river was monitored for the period of twelve months (September 2004 to August 2005) for assessing the impact of Asia's highest dam, Tehri Dam. Comparative data on diversity of macroinvertebrates revealed that the number of taxa in the downstream stretch, especially close to the dam was significantly reduced.