Bhavanisagar dam is constructed on the Bhavani River. The dam receives water from two main catchment areas in the Western Ghats. The water is fed into the Bhavani river known as Upper Bhavani. The eastern catchment area includes the Upper Bhavani, Avalanche and Emerald lakes, Kundha, Gedhai, Pillur and Nellithurai. The western catchment area includes Portimund, Parson's valley, Pykara, Glenmorgan, Chinkara, Maravakandy, Moyar, and Thengumarahatta. The dam is fed by both Southwest and Northeast monsoons.