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September 2007

Saline intrusion into the aquifers

- Carel

French scientists warn of intrusion of salt water into the aquifers of the bioregion. This may well be the biggest environmental threat Auroville and all the villages in the area will ever have to face.

After years of monitoring, a study of the water use in the Kalivelli region has been finalized. Several presentations were made to the residents of Auroville, major Auroville working groups and to the water-related government agencies of Tamil Nadu, Pondicherry and Central Government in April and May this year. The study, conducted jointly with national and international scientists, indicates that the aquifers in the whole area, including those below Auroville, are being emptied faster than they are being replenished. The withdrawal rate is about 4 times more than the recharge. The net deficit is estimated at 500 million cubic metres per year. Agriculture accounts for most of the ground water extraction. A large volume is also lost to the sea through uncollected run-off.

In some places, the water level in the aquifers has dropped far below sea level (up to 50 metres). This will have dramatic consequences. The study estimates that within a period of 5 years, the groundwater will turn saline and become unusable for human consumption and agricultural use. This would affect a population of approximately 400,000 people, including the Aurovilians.

The problem is not new. Seawater intrusion is already occurring in the southern areas of the bioregion along the coast. But can something be done to halt this aquifer depletion? Is it possible to reverse the process and, in the long run, maintain the water balance within the affected aquifers?

A group of concerned Aurovilians, the Water Group, believes it has a solution that does not damage the status of Kalivelli tank as a Wetland of International Importance under the Ramsar Convention while being replicable in other threatened or affected areas. They propose to harvest the huge volumes of rain water that are now lost to the sea, and use it to recharge the groundwater level. At the same time, appropriate irrigation and agricultural practices have to be introduced.

The problem has to be tackled at four different levels. The first is to afforest the wastelands above the aquifers and along the water ways over an area of 1015 sq. kilometres. Forestation would slow down monsoon rain run-off, and enable the water to infiltrate into the ground and replenish the aquifers. The second work to be done is to build recharge structures to ensure that water reaches the aquifers; the third to repair the supply and drainage channels to the tanks in the area, so that bigger storage becomes available. And, lastly, a programme has to be implemented to encourage the farmers in the region to convert to new methods of sugarcane and rice cultivation which use less water. This should be coupled with incentives to switch to water-saving practices and to organic agriculture.

The total cost of the project is estimated at Rs. 125 crores (US $ 30 million), for which funds will have to be raised. The Water Group proposes that a body is created under the Auroville Foundation, chaired by the Secretary and endorsed by the Governing Board, to raise funds and then plan, implement and monitor this project in coordination with the local authorities. This body can then apply to Indian Government agencies for securing funds.

Desilting an Edaiyanchavadi tank.

Auroville can play a central role in this project, says the Water Group. Auroville is among the few organisations in India that has the technical expertise to contribute all these proposed inputs on the scale required. Once implemented, the project will be an excellent prototype for the rest of the Coromandel Coast , where similar depletion of coastal aquifers is taking place at an alarming rate.

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