Tamil Nadu, save for a few regions, does not receive much rain from the SouthWest monsoon which is the main monsoon of India. Tamil Nadu receives its rains mainly from the North East monsoon which is less copious.
During the whole season, it rains for only 15 to 20 days in a year, which means about only 100 hours of rain and this has to be used for the remaining 8660 hours of the year. This scenario has led to the popular belief that Tamil Nadu is rainfall deficient and hence water deficient.
But this has been the rainfall scene for thousands of years.
While the modern generation looks at this land as being rainfall and water deficient, even till as recently as 150 years ago, the people of Tamil Nadu seem to have enjoyed great prosperity and culture, which can come only when there is sufficient water in this land for its people, flora and fauna.
The people of Tamil Nadu had realized that this land is on the leeward side of the Western Ghat. The gradient of the land was sloping from west to east, draining into the Bay of Bengal.
Recognizing this topography, they built Eri, tanks, dotting all over the landscape to harness the rains where its falls and pass it on to places where it did not rain. It was an ingenious, intricate web, a chain of tanks – system tanks, Eri, Oorani, Anaikat and a whole host of local water harnessing systems, which were interconnected. The rivers and their distributaries were the arteries. The principle behind it was the heart of sharing.
If it rained anywhere in the Carnatic region, all the tanks downstream would also receive water. Finally, if the water was let out from the Sri Vaikuntam Eri in southernend of Tamil Nadu, near Tirunelvelli, to the sea, it meant that all the Eri of the Carnatic land were brim full by then.
These Eri and the web, were all built by the locals themselves during the Pallava period, from 400 CE to 1100 CE. These have since then sustained the land and made it prosperous for the next thousand years and more. These were all people designed and people maintained.
It was after the 1857 war of Independence that the British administrators decided to wrest control of the water bodies from the local people.
To this effect, a Public Works Act of 1857 was promulgated and the Public Works Department (PWD) was created to control the water bodies of the land. This passed the control of the water bodies from the people to the government which soon led to the dereliction in their maintenance and eventual disrepair. Soon the people of Tamil Nadu were deprived of their life supporting Eri and therein, rests the tale of the water shortage of Tamil Nadu.
A perspective of this is discussed in our article on solution to the Cauvery Water Issue.
The Tamil Nadu State Legislative Assembly passed the Farmers Management of Irrigation Systems Act 2001 which is a step in the right direction of giving back the control of the water bodies back to the farmers.
Today, there is a renewed energy in the youth to revive the tanks in disrepair in their local areas. While this is a good step in restoring ground water in that region, this stand alone tank will be of no avail when that region does not receive its due rains in any year.
The complete solution lies in reviving the connecting ducts between these tanks as well as reviving the entire web, the Chain Tank system, so that irrespective of wherever it rains in the Carnatic region, the Eri of every village of this region is always full. Not a trivial task. It is a challenge indeed, in terms of plan, effort and cost.
A possible way out for the overall revival is discussed in detail in our book You Turn India in the Bharath Gyan series.