The Grand Anicut, also known as the Kallanai, is an ancient dam built on the Kaveri River near Tirchi in the state of Tamil Nadu in southern India. It was built by the Chola king Karikalan around the 2nd Century BC and is considered one of the oldest water-diversion or water-regulator structures in the world, still in use.

The dam was re-modeled by the British during the 19th century. In 1804, captain Caldwell, a military engineer was appointed by the British to make a study on the Kaveri river and promote irrigation for the delta region.

source: https://en.wikipedia.org/wiki/Kallanai_Dam