Mullai periyar Dam, is a masonry gravity dam over River Periyar, with a height of 155 feet and length 1200 feet and is located 3900 feet above m.s.l. on the High Ranges (Cardamom Hills) of Western Ghats in Thekkadi, Idukki District of Kerala, India. It was constructed in 1895 by the British Government, over the headwaters of the west-flowing Periyar River and its tributary Mullaiyar, to divert water eastwards to Madras Presidency area (the present-day Tamilnadu). The Periyar National Park, Thekkady is located around the Periyar reservoir formed by the backwaters of this dam. The dam is operated by the Government of Tamil Nadu.
You can read more in Tamil: Envazhi.com