Globally Important Agricultural Heritage Systems (GIAHS)

Grand Anicut (Kallanai) and associated farming system in Cauvery Delta Zone of Tamil Nadu



Agriculture in the Cauvery Delta region has been practiced for centuries supported by the inundation during the flash floods and the monsoon rains that closely follow. With the passage of time the river courses were getting slowly silted up. The crucial point on the river course as it enters the delta is the Upper Anicut site, where the Cauvery bifurcates into Cauvery and its tributary Coleroon. The Cauvery again spills into Coleroon through a short spill course called Ullar. Situations should have arisen long before in the past when the flood flows carried by the southern Cauvery arm, instead of flowing through the various rivers and channels in the delta, found their way into Coleroon through this Ullar leaving the delta high and dry.  A need for a structure across the Ullar to raise the water level to gain command for flow through the delta was felt. Thus came the Kallanai (Stone dam), an ancient dam rightly called as “Grand Anicut” by the British Engineers in India in admiration of the grandeur of the structure.

Grand Anicut was built by the Great Chola Emperor Karikala Cholan on river Cauvery at the Ullar head in the 2nd Century AD. It is a marvelous piece of hydraulic structure built across a mighty river in its sandy bed when science had not developed enough to build structure on permeable foundations. It is perhaps, the earliest irrigation work in the world still functioning as efficiently as any modern hydraulic structure. It has kept the Cauvery Delta intact, alive and highly productive over a long period of twenty one centuries, surviving the furies of floods which should have been unimaginably devastating in the past when there were no structures in the upper reaches of Cauvery, to obstruct the flood flows. The Kallanai is a massive dam made of stone, 329 meters long, 18.3 meters wide and 5.49 meters tall, built with the main purpose of diverting the Cauvery water to the fertile delta region for irrigation.