Ramganga River is the largest of the few perennial sources of water in the Park. Crucial for Corbett, the rain-fed river originates near Gairsain in the Lower Himalayas. After its origination, the river travels a length of 100 km before entering the national park. Once in the park, the river flows for 40 km till Kalagarh, before entering the plains.The river gathers waters from the Palain, Mandal and Sonanadi Rivers, during the run through the Park. Aquatic species like mahseer fish, the endangered gharials, mugger crocodiles, otters and turtles find abode in the river. Owing to its rich fish population, the river attracts many migratory bird species, especially water birds from Europe and Central Asia, during winters. The river also serves as an important source of livelihood for many species of birds, like kingfishers, fish-eagles, terns and storks.