The Idukki Hydroelectric Project is one of the top ten highest Arch Dams in the world and the third highest in India after the Tehri Dam (Uttarakhand) and Bhakra Nangal Dam (Himachal Pradesh).
The idea of a Hydroelectric Project over the Periyar River occurred to W. H. John, the then superintendent of Malankara Estate. John, in an article published in Malayala Manorama Newspaper in 1935, detailed the prospects of such a project. Kuravan and Kurathi hills, the core area of the project, were introduced to John by Chemban Kolumban, a member of the local Oorali tribe. Kolumban with his wide knowledge of the forest later became an accomplice of the engineers who came for site inspection. As a token of appreciation there stands a memorial to Kolumban on the dam site.
The Project was commissioned by then Prime Minister of India, Indira Gandhi in 1976. The reservoir has over 2 billion tons of water contained in three dams-Idukki, Cheruthoni and Kulamavu. Idukki dam is used to store the water while the latter two are meant to route it to the powerhouse. To this day, the Idukki project supplies a major portion of the electricity in the State.