10 Jun Grand Anicut Design
From ancient times to modern times, civilizations build dams of varying designs to divert water flow, irrigate lands and generate power supply. There is one in particular which has the reputation for fascinating historians and engineers that come across it.
It is the 2000-year-old Grand Anicut located in Tamil Nadu, India. This Indian engineering masterpiece is one of the designs throughout history to inspire the perfection of dams used today.
We’ve gathered information containing Its history, unique construction and we also compared the structure to dams used today.
Grand Anicut and Dams
What is a Dam?
A dam is simply a barrier built across a river or any large water source. Its function is diverting water; to prevent flood or for irrigation and also to retain water for domestic use and power supply.
What is an Anicut?
This is a dam built across a stream or river for maintaining and regulating irrigation.
In terms of function, a dam can clearly do more than the Grand Anicut. A standard dam has the ability to divert and retain water from a large water source for water supply and power generation. The Grand Anicut, on the other hand, was designed to retain water and divert the surplus to irrigate lands.
When considering materials used, a dam can be made of a combination of several materials such as lumber, concrete, stones, and steel. The Grand Anicut is made of rocks, landfill, and concrete, given they were the standard materials required for structural construction in the past.
The general design is another factor that showcases the difference between a dam and the Grand Anicut. There are various designs a dam can have which depends on certain conditions for building them. As the Grand Anicut, it is a rock fill, gravity dam that retains and diverts river currents.
The Grand Anicut (Kallanai Dam) History
The Grand Anicut was originally built by King Karikalan of the Chola dynasty between the 100BC – 100AD in Thanjavur District, India. The purpose of the structure was to divert the flow from the Kaveri river across the fertile delta region in order to irrigate lands via canals In the northern delta branch.
After the invasion by the British, they were fascinated with the structure and saw that it could be improved. So a military engineer known as captain Caldwell was assigned by the British military to perform a study on the Kaveri river and promote irrigation in the fertile delta land.
Caldwell discovered large amounts of water from the river passes through the Grand Anicut, in such a way the dam diverts minimal water for irrigation purposes. Caldwell’s initial solution to the problem was to raise the height of the dam sunken stones to 27 inches. This was predicted to increase the capacity of the dam for irrigation purposes.
Another individual who was involved in the project also proposed the idea that under-sluices should be built across the river with outlets that lead to the Kollidam river. The idea helps to prevent the formation of silt whilst diverting large amounts of water.
After the modification of the Grand Anicut, the output of the dam vastly increased. By the early 20th century, the dam was able to irrigate over 1 million acres of land. Farmers in the fertile delta of Tamil Nadu were amazed by the achievement of the great structure, they demanded the Government should honor King Karikalan of the Chola dynasty, who originally built the Kallanai dam.
The Grand Anicut also is known as the Kallanai Dam is a simple check dam constructed across the direction of flow of the Kaveri river in order to divert water into the fertile delta of Tamil Nadu.
Its unique structure majorly involves several large unhewn stones extending across the Kaveri, stuck in the Cauvery river to divert the flow of current to the fertile delta. The dam is 329 meters long, 20 meters wide and 5.4meters high. It was able to irrigate 69,000 acres of land in the fertile delta.
Before the modifications made by the British, the original Kallanai dam had some unique design features which worked well for both the environment and residents. These features include the curved shape of the masonry section, an irregular descent, and a sloping crest.
These features reshaped the water current flowing towards the dam smoothly and it had a good sedimentation process.
The Original Construction
Before the alteration made by the British, the dam was originally constructed by king Karikalan completely out of rocks. The process involved in the construction includes cutting and placing rocks.
Rock cutting process includes punching holes into the rocks, inserting wedges into those holes, apply water and streaking.
Placing the Rocks
First, the rocks are placed across the Cauvery river and the heavy stones are then placed in their respective places. The stones depend on the external thrust and push caused by the river’s currents to maintain its stability.
The stones can’t be moved by fast-moving water, so the builders adopted a method of immersing the heavy stones into the river by loading and erosion process.
The process involves the placement of one stone in the bottom and one on top of it. They will depend on erosion to correct the position.
The foundation of the dam is secured as it is made up of sand bed. It gives the dam a great foundation which makes the Grand Anicut strong and durable. That’s why it was able to last throughout several years before it was tampered by the British.
The Lower Anaicut
This structure is a replica of the Grand Anicut. It was built by Sir Arthur Cotton during the 19th century across the Coleroon river. It is regarded as the tributary of Cauvery (Coleroon and Kaveri river).
One of India’s oldest surviving dams is nothing short of a national treasure. It is a structure passed down to several generations and still serves the populace around it. This makes the design truly an inspiration to the for the largest dams we use today. The only downside to its construction is the modification made by the British. Although, it improved irrigation of the fertile Delta, the unique design by king Karikalan was good for both the people and the environment.