Thirsty Indian metropolis finds an answer in the rain
Chennai has devised ways to capture and reuse rainwater to help solve its shortage.
from the March 20, 2008 edition
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The rainwater that stagnates on roads or journeys seaward through storm drains after downpours needs to be diverted into strategically located recharge pits, Dr. Raghavan says. "Recharging groundwater is like putting money in the bank – it can be withdrawn during lean, drought years."
The aesthetically pleasing temple tank also serves a similar purpose and helps replenish groundwater in that neighborhood.
Even when rains are plentiful in Chennai, the demand for drinking water is high. Those with money turn to private suppliers, who bring in tankers of well water from the outskirts of the city. With all this rampant water-mining, the importance of replenishing the groundwater cannot be overemphasized, Raghavan says.
The Indian city of Bangalore has taken a leaf out of Chennai's book. "Harvesting rainwater, once an alternate source of water, is fast becoming mainstream," says Viswanath Srikantiah, founder of Bangalore's Rainwater Club.
Though rainwater harvesting has come back into vogue, the water woes of India's megacities will not vanish. Consumption patterns must change if water is to remain a renewable resource.
"When we had abundant supply of water, we used it a certain way. Now supply is less, we have to learn to live accordingly," Professor Janakarajan says.
A saying in Tamil, Chennai's local language, admonishes wastrels for spending money like water. Now, residents here may need to learn to spend water like money instead.
The temple 'lakes' of South India
Harvesting rainwater is an age-old practice in India. Traditionally, it has meant storing water in tanks or reservoirs – known as erys in Tamil, the language of southeastern India.
"These tanks were marvelous examples of indigenous engineering skills and ingenuity," says T.M. Mukundan, author of "The Ery Systems of South India."
The soil type and topography of the site would dictate the layout of each ery. The reservoirs recharged the groundwater, and provided flood control during periods of heavy rainfall. Since the erys were interconnected, the overflow from one ery automatically drained into another.
During British rule of India (1858-1947), many of the ery systems fell into disuse and silted up as centralized water supplies took their place.
"Many of these erys have disappeared because of encroachment – due to urbanization or other reasons," says Prof. S. Janakarajan of the Madras Institute of Development Studies. But the remaining agricultural tanks, about 2,500 of them, can be restored, he says, and their surplus water transferred to thirsty cities.
Governments should declare that the tanks and the areas around them are ecologically sensitive areas and penalize encroachers, as the first step in protecting these water resources, he says.
In southern India, many temple tanks once served as public spaces where the community would gather. The city of Chennai alone has 39 temple tanks: The Kapaleeswarar temple tank in its Mylapore district is one of the most prominent.
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