The Kunthipuzha River drains the entire 15 km length of the park from north to south into the Bharathapuzha River. Kunthipuzha River divides the park into a narrow eastern sector of width 2 kilometers and a wide western sector of 5 kilometers. The river is characterized by its crystal clear water and perennial nature. The main tributaries of the river, Kunthancholapuzha, Karingathodu, Madrimaranthodu, Valiaparathodu and Kummaathanthodu originate on the upper slopes of the eastern side of the valley. The river is uniformly shallow, with no flood plains or meanders. Its bed falls from 1,861 m to 900 m over a distance of 12 km, the last 8 km being particularly level with a fall of only 60 m. Kunthipuzha is one of the less torrential rivers of the Western Ghats, with a pesticide-free catchment area.