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CHENNAI: Endangered Urban Tanks

Water has always been a scarce commodity in Chennai. The situation today is so appalling that water supply has been restricted to every alternate day. It started deteriorating after the last three consecutive drought years.

Water supply for Chennai city was first designed in 1872 to meet the demands of a population of 0.47 million by the then special executive engineer to the government, Fracer. The flow from Kortalliar river was diverted to Cholavaram and Red Hills, which were connected to the city through channels. It supplied 32 million litres per day (mld) of water to the city. The supply was supplemented by 159 mld from the Poondi reservoir in 1944. The capacity of Red Hills and Cholavaram was increased in the late 1960s. The projected demand for the year 2001 is 283 mld.

The city's main source of water is the Red Hills lake, with a total capacity of 3,000 million cubic feet. The total capacity of Poondi, Cholavaram and Red Hills reservoirs is 6,000 million cu ft. The water from these three sources has been completely diverted from irrigation to supply for domestic and industrial needs.

Tank system

Tamil Nadu has as many as 39,202 tanks, out of which about 124 tanks are in the chennai Metropolitan Area (MMA). The tanks have a waterspread area of approximately 5.5 per cent of the MMA area (waterspread area is 63.8 sq km, and MMA area is 1,167 sq km). In addition, there are 39 temple tanks in the city. A tank restoration scheme was launched in the city in 1883 on the recommendations of the Famine Commission. Under the scheme, a memoir detailing the hydrological features was drawn up. Most tanks in the area form 'system eris' or tanks which are a part of integrated water harvesting systems, and are situated in the basin of one of the four rivers flowing through the area.
But urbanisation has taken its toll - the stormwater courses feeding these tanks have disappeared and water flows into the sea without filling these tanks.

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