[2][3] It is located 881 m (2,890 ft) above the sea level, on the Cardamom Hills of the Western Ghats in Thekkady, Idukki District of Kerala, India.

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).

[19] The Periyar river which flows westward of Kerala in to the Arabian Sea was diverted eastwards to flow towards the Bay of Bengal to provide water to the arid rain shadow region of Madurai in Madras Presidency which was in dire need of a greater supply of water than the small Vaigai River could provide.

[18] 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.

Caldwell discovered that the excavation needed would be in excess of 100 feet in depth and the project was abandoned with the comment in his report as "decidedly chimerical and unworthy of any further regard".

[18] On 29 October 1886, a lease indenture for 999 years was made between the Maharaja of Travancore Moolam Thirunal Rama Varma, and the British Secretary of State for India for Periyar Irrigation Works.

[28] In 1947, after Indian Independence, Travancore and Cochin joined the Union of India and on 1 July 1949 were merged to form Travancore-Cochin.

According to the renewed agreement, the tax per acre was increased to ₹ 30, and for the electricity generated in Lower Camp using Mullaperiyar water, the charge was ₹ 12 per kiloWatt per hour.

[27] In Madurai, Pennycuick's statue has been installed at the state PWD office and his photographs are found adorning walls in peoples homes and shops.

[27] The dam created a reservoir in a remote gorge of the Periyar river situated 3,000 feet above the sea in dense and malarial jungle, and from the northerly arm of this manmade waterbody, the water flowed first through a deep cutting for about a mile and then through a tunnel, 5704 feet in length and later through another cutting on the other side of the watershed and into a natural ravine and so onto the Vaigai River which has been partly built up for a length of 86 miles, finally discharging 2000 cusecs of water for the arid rain shadow regions of present-day Theni, Dindigul District, Madurai District, Sivaganga District and Ramanathapuram districts of Tamil Nadu, then under British rule as part of Madras Province (Sandes, 1935).

According to a report by the Kerala Forest Research Institute, the protected area surrounding the dam and reservoir is classified as a biodiversity hot spot.

[44][45] During a 2011 scanning of the Mullaperiyar dam using a remotely operated vehicle by the Central Soil and Materials Research Station on directions from the Empowered Committee of the Supreme Court, the Kerala Government observer opined that "mistakes in the strengthening works carried out by Tamil Nadu" in 1979 damaged the masonry of the dam.

[51] A 2009 report by IIT Roorkee stated that the dam "was likely to face damage if an earthquake of the magnitude of 6.5 on the Richter scale struck its vicinity when the water level is at 136 feet".

[52] On 18 February 2010, the Supreme Court decided to constitute a five-member empowered committee consisting three judges and two technical experts to inspect and study all the issues of Mullaperiyar Dam and seek a report from it within six months.

[53] The Bench in its draft order said Tamil Nadu and Kerala would have the option to nominate a member each, who could be either a retired judge or a technical expert.

The five-member committee will be headed by former Chief Justice of India A. S. Anand to go into all issues relating to the dam's safety and the storage level.

[54] However, the then Leader of Opposition i.e., the late Chief Minister of Tamil Nadu J. Jayalalithaa objected to the TN Government move.

[57] However, Supreme Court refused to accept Tamil Nadu's request to scrap the decision to form the empowered committee.

[58] The Empowered Committee headed by the former Chief Justice of India A.S. Anand, in its findings concluded that the dam is "structurally, hydrologically safe, and Tamil Nadu can raise the water level from 136 to 142 feet after carrying out repairs.

"[59] The control and safety of the dam and the validity and fairness of the lease agreement have been points of dispute between Kerala and Tamil Nadu states.

[60] Supreme court judgment came on 27 February 2006, allowing Tamil Nadu to raise the level of the dam to 152 ft (46 m) after strengthening it.

[63] In 2006, the Supreme Court of India by its decision by a three-member division bench, allowed for the storage level to be raised to 142 feet (43 m) pending completion of the proposed strengthening measures, provision of other additional vents and implementation of other suggestions.

[66] The court has ruled that Tamil Nadu can increase the water level to 142 feet and constituted a permanent Supervisory Committee in order to take care of the affairs relating to maintenance of the Mullaperiyar Dam.

[67] In 2014 while passing the final verdict, the Supreme Court constituted a permanent Supervisory Committee to oversee all the aspects of the Mullaperiyar dam.

[76] The Supreme Court, which declared the dam as hydrologically and seismically safe previously in 2014, asked Kerala and Tamil Nadu states to act seriously as 'people's lives are at risk' in a U turn.

[77][78] Tension rose again when Tamil Nadu opened 10 shutters of the dam after midnight without giving proper warning, causing floods along the banks of the Periyar River.

This resulted in Chief Minister of Kerala, Pinarayi Vijayan sending a letter to his Tamil Nadu counterpart to open shutters of dam only at daytime and with proper warnings.