The Periyar Tiger Reserve covers the area inclusive of and around an artifical lake, created as a result of the construction of the Mullaperiyar Dam. The river and the dam are so called because the dam is located after the confluence of the Mullayar and Periyar rivers.
The dam is 155 ft high and 1200 ft long. Its construction began in 1887 and was completed in 1895. The first dam, which was built by the British Corps of Royal Engineers, was washed away by floods. Thereafter, a second stonework dam was built in 1895.
The dam's purpose was to divert the waters of the west-flowing River Periyar eastward to the arid rain shadow regions of the Theni, Madurai, Sivaganga and Ramanathapuram districts of Tamil Nadu. The construction of the dam paved the way for the creation of the artificial lake at the centre of the Reserve.
The dam was built to meet the water requirements of the temple town of Madurai in Tamil Nadu. Hence, though the dam is situated in Kerala, it is operated by the Tamil Nadu Government. It was according to a 999-year lease agreement made during the British rule that the operational rights were handed over to Tamil Nadu.
The dam was constructed to divert the flow of the river towards the east as the west-flowing River Periyar created floods in the Travancore region. The construction was carried out by the British Corps of Royal Engineers under the leadership of Pennycuick. Once built, the dam prevented the floods and provided water to the city of Madurai. It also helped to transform some barren land in Tamil Nadu to fertile regions. The water from the reservoir reaches Theni, Madurai, Sivaganga and Ramanathapuram districts of Tamil Nadu though tunnels that cut across the Western Ghats.