The Asan Conservation Reserve is a 444-hectare stretch of the Asan River running down to its confluence with the Yamuna River in Dehradun district of Uttarakhand. The damming of the River by the Asan Barrage in 1967 resulted in siltation above the dam wall, which helped to create some of the Site’s bird-friendly habitats. These habitats support 330 species of birds including the critically endangered red-headed vulture (Sarcogyps calvus), white-rumped vulture (Gyps bengalensis) and Baer’s pochard (Aythya baeri). More than 1% of the biogeographical populations of two waterbird species have been recorded, these being red-crested pochard (Netta rufina) and ruddy shelduck (Tadorna ferruginea). Other non-avian species present include 49 fish species, one of these being the endangered Putitor mahseer (Tor putitora). Fish use the site for feeding, migration and spawning. As well as this support for biodiversity and the hydro-electricity production of the Barrage, the Site’s role in maintaining hydrological regimes is important.