 The Periyaru 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.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.The Vaigai was dammed by the Vaigai Dam to provide a source for irrigating large tracts around Madurai.