The Oldest Dam in the World – Grand Anaicut
The world’s largest Deltaic Region is Indian Ganga Brahmaputra delta, which has spread over the area of 1,00,000 km2. Cauvery Delta is one of the largest Deltas in India enriching the agricultural crops in Tamilnadu.
“What is Delta Region?”
The landscape formed by the deposits of flood water, sediments over the period of long time at the river mouths. River Deposits are geologically known as Alluvial Soil, they consist mostly fine grained soils such as Clay, Silt & Fine Sand. They are Minerals and nutrients rich fertile soil with water holding capacity; Suitable for close spacing crops like Paddy. We are cultivating paddy across vast acreage in Thanjavur. We call thanjai as “Nerkalanchiyam of Tamilnadu” Whch is the reason behind this name?
Chola King Karikal Peruvazhatthan
This is how it began in the ancient time. That is the timeline 100 BC, when the rulers are the famous Cholas. Water drained into theBay of Bengal in large scale causing floods and during the summer, drought was the scenario. Diverting the excess water would enable the cultivation in more area, but the topography needs a dam structure across the river for the diversion.
Chola King Karikal Peruvazhatthan noticed the issue. He planned India’s first and world’s fourth head work to divert the water and utilize it efficiently.
Alluvial soil can’t be as good foundation platform for Structures like Dam, since they will subject to settlement and bearing capacity failures against the load. The downstream may also undergo to seepage and quicksand condition because of the soil gradation and elevated water level in the upstream side of the dam. 2 lakh cusecs was the maximum river flow in the proposed diverting location. Tamilians had a solution to make the construction possible.
Highlights of the Dam Construction
1. Base Construction: The challenging part was laying the foundation for the dam structure under high discharge of water. Karikalan had chosen stones of size 2 feet (about 69 cm) and laid at the proposed location. Stones had been sinking for years due to its self weight and the scouring offered by the passing water.
Using Clay pastures, stones were bound one after another during the sinking. Finally a sound platform for the dam structure had created over many years.
2. Flow Direction: Height of the dam was fixed as 5.4 meters (18ft), to rise and divert the water flow towards the water less delta land. Total length is 329 meters with a base width of 20 metres.
3. Storage & Usage: Irrigation network system serving for 69,000 acres of land had been formed at the ancient time. Kallanai can store a maximum of 2.8 million cubic meters of water. But it is just 0.1 % of Mettur Stanley Reservoir capacity (2647 MCM – 120ft).
After the Period of Karikalan
- Maintenance works had carried out by the British Captain Coldwell during 1804.
- When the heavy floods & droughts were affecting the Cauvery basin, Arthur cotton was appointed during 1839 to take care of irrigation orientations in the basin . Later on, he came to be famously known as Father of Irrigation works in India.
- While doing research on the kallanai and rehabilitating the base, he was mesmerized about the construction practices of Karikala cholan on kallanai foundation. He named the Kallanai as Grand Anaicut.
- During the Twentieth century irrigation commanded area had increased to 10 lakh acres through four streams known as Kollidam River, Venna River, Cauvery River and Puthu River.
Being an Example of Chola’s Proficiency in Construction Practice, Now it is the one and only oldest dam in the world still functioning and making the stand around 2000 years in Tamilnadu.
Let us proudly say, Long Live Grand Anaicut!!!