Silent Valley is located at Mukkali, Mannarkkad, Padavayal in Kerala, at the core of the Nilgiri Biosphere Reserve .
In 1976, Kerala State Electricity Board planned a construction of a 240 MW hydroelectric project, the Silent Valley Hydro-Electric Project (SVHEP), over the Kunthipuzha River flowing through the Palakkad and Mallapuram districts, intended to submerge 8.3 sq km of forest land . The plan for construction of the dam, announced already in 1973, attracted attention of environmentalists not only in Kerala state but also all over the globe. Romulus Whitaker, founder of the Madras Snake Park and the Madras Crocodile Bank, was probably the first person to draw public attention to the small and remote area. Also the poet activist Sugathakumari played an important role in the Silent Valley protest and her poem "Marathinu Stuthi" ("Ode to a Tree") became a symbol for the protest from the intellectual community and was the opening song/prayer of most of the "save the Silent Valley" campaign meetings. People were concerned about the fact that the construction of the dam will submerge vast amount of land and will severely destroy the rich ecological flora and fauna of that region. People expressed their concern and it triggered a wave of protests through the different mode of protest all across the state. May environmentalists, scientists, concerned people and common people also joined the demonstration. The protest from the Kerala state was further intensified when people from all over the country joined the protest. Soon it became India's major and perhaps the first environmental movement with a far reaching consequence . In 1978 Indira Gandhi, Prime Minister of India, approved the project, with the condition that the state government enact legislation ensuring the necessary safeguards. Also that year IUCN (Ashkhabad, USSR, 1978) passed a resolution recommending protection of lion-tailed macaques in Silent Valley and Kalakkad and the controversy heated up. In 1979 the Government of Kerala passed legislation regarding the Silent Valley Protection Area (Protection of Ecological balance Act of 1979) and issued a notification declaring the exclusion of the hydroelectric project area from the proposed national park. In 1982, a multidisciplinary committee with Prof. M. G. K. Menon as chairman and Madhav Gadgil, Dilip K. Biswas and others as members, was created to decide if the hydroelectric project was feasible without any significant ecological damage. Early in 1983, Prof. Menon's Committee submitted its report. After a careful study of the Menon report, the Prime Minister of India decided to abandon the Project. On September 1, 1986 Silent Valley National Park was designated as the core area of the Nilgiri Biosphere Reserve. The area is now considered as 'hot spot' . The 'Save Silent Valley' movement was a grand success for all time environmental movement in India. Beside this, it is a source of inspiration for similar agitations. The ‘Narmada Bachao Andolan’ and the ‘Tehri Dam’ protests are highly motivated by that campaign .