The Periyar, the Chalakudy, the Karuvannur, the Kurumali River (main tributary of the Karuvannur River) and the Ponnani (Bharatha Puzha) are the main river systems in the district. They take their origin from the mountains on the east, and flow westward and discharge into the Arabian Sea. There are a number of tributaries also joining these main rivers. There are waterfalls such as Athirappilly Falls which is widely known as the "Indian Niagara" nowadays. This is the only district in Kerala with the presence of both Periyar and Bharathappuzha, though they flow only a small distance through the district.