The Mullaperiyar Dam or Mullaiperiyar Dam is a masonry gravity dam on the Periyar River in the Indian state of Kerala It is located 881 m (2,890 ft) above mean sea level, on the Cardamom Hills of the Western Ghats in Thekkady, Idukki District of Kerala. It was constructed between 1887 and 1895 by John Pennycuick and also reached in an agreement to divert water eastwards to the Madras Presidency area (present-day Tamil Nadu). The Periyar National Park in Thekkady is located around the dam’s reservoir. The dam is located in Kerala on the river Periyar, but is operated and maintained by Tamil Nadu state. By reports on 21 November 2014, Mullaperiyar water level touches 142 feet for first time in 35 years. The reservoir again hit the maximum limit of 142 feet on 15 August 2018, following incessant rains in the state of Kerala.
The dam created the Periyar Thekkady reservoir, from which water was diverted eastwards via a tunnel to augment the small flow of the Vaigai River. The Vaigai was dammed by the Vaigai Dam to provide a source for irrigating large tracts around Madurai.