Mullaperiyar Dam (Malayalam: മുല്ലപെരിയാര് അണക്കെട്ട്), 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 based on a 999-year lease agreement made during erstwhile British colonial rule, between the British Government (Madras Presidency) and the Travancore Maharajah. The catchment areas and river basin of River Periyar downstream include five Districts of Central Kerala, namely Idukki, Kottayam, Ernakulam, Alappuzha and Trissur with a total population of around 3.5 million. Water diverted eastward flows through a tunnel from the dam, joins River Vaigai in Tamilnadu, and is used for irrigation and power generation in Tamilnadu. The Periyar Power Station in Lower Periyar, Tamilnadu generates hydro-electricity from the diverted waters. The dam has been a bone of contention between the State Governments of Kerala and Tamilnadu, with Tamilnadu demanding raising of water level in the reservoir to increase flow of water to Tamilnadu, and Kerala objecting to this on the grounds of safety of the 116 year old reservoir that is built using lime and surkhi mortar. Earthquakes in the area have further highlighted safety issues and concerns. Various issues are still being adjudicated by the Supreme Court of India.. Mullaperiyar has been a hot issue politically and legally between the two Southern States of India, namely, Tamilnadu and Kerala.