 It consists of a main dam, spillway on its left and an auxiliary dam (or "baby dam") to the right.Its reservoir can withhold of water, of which is active (live) storage.The unique idea of harnessing the westward flowing water of the Periyar river and diverting it to the eastward flowing Vaigai river was first explored in 1789 by Pradani Muthirulappa Pillai, a minister of the Ramnad king Muthuramalinga Sethupathy, who gave it up as he found it to be expensive.