Kosi is a perennial river whose catchment area lies partially in Corbett National Park
. The river forms the eastern boundary of the park from Mohan through Dhikuli till Ramnagar
. It acts as a source of drinking water for animals during summer. Kosi often changes its course and is notorious for its damaging torrents during monsoon. The river is inhabited by Mahseer fish and offers a temporary settlement for several migratory birds in winter. The precipitous slopes flanking the river at some places are favorite grounds for goat-like creatures called Grey Goral.