Eettachola Aar, Karinthiri and Menachery rivers are perennial in nature and are the main source of drainage from Mankulam. These rivers merge together at Anakulam, then flow towards west and join the Pooyamkutty River. Karinthiri is the common boundary, which divides the Mankulam and Anakulam Ranges. The Pooyamkutty River joins Edamalyar, which is a tributary of Periyar River.