Ramganga River is the largest perennial river that flows in the Corbett National Park. This rain fed river originates in the lower Himalayas and before entering the park, it covers a distance of 100 km. After entering, it flows through a distance of 40 km till Kalagarh. The Ramganga River is home to several aquatic species such as mahseer fish, gharial, mugger, turtles and crocodiles. Moreover, various migratory birds across Asia and Europe flock here in the park during winters and can be spotted at the banks of this river. The river is a main source of water for various residential birds of the park such as kingfishers, terns, storks and fish-eagles.