 The Chennai city river conservation project, inaugurated by Tamil Nadu Chief Minister M Karunanidhi on January 1, involving an expenditure of Rs
720 crore, is aimed at improving the waste water disposal network in the city.
Scheduled to be completed by September 2003, the project also aims at preventing noxious substances from reaching the waterways, utilising the useful substances available, and returning the treated water to the environment.
The Adyar in the south and Cooum in the north of Chennai are the two major waterways flowing from west to east before they join the sea on the east coast.
Buckingham Canal, a man-made waterway, runs along the coast from north to south through major sections of Chennai. The Otteri Nullah and Captain Cotton Canal are the tributaries to Buckingham Canal in the north of Chennai. Similarly, the Mambalam canal, flowing from the central part of the city, drains into the
Adyar river.
According to a study by Chennai Metrowater, these waterways have been functioning as flood carriers with flows for about two months in a year during the monsoon rains.
The flow in these water courses during the remaining part of the year is mainly due to discharge of treated, partially treated and untreated sewage through more than 300 outfalls meant for storm water discharge.
Such flows result in accumulation of large volume of sludge and formation of sand bar in the mouth of the rivers.
These outflows have created significant problems for flood protection systems, storm water drain network and public health leading to overall environmental degradation.
The sewerage network of Chennai, first installed in 1891, has grown to a length of 2,300 km. Though sewage service is extended to 96 per cent of the areas, the city has earned the distinction of being the highest sewered metropolis in the country.
For operational reasons, the city sewerage network has been divided into five waste
 water drainage zones each with its own interception, collection, diversion and treatment systems.
This network is operated through 134 pumping stations which ultimately convey the collected sewage to treatment plants at Kodungaiyur, Koyambedu, Nesapakkam, Perungudi and
Villivakkam.
After Krishna river water from Andhra Pradesh started flowing into the city reservoirs, the capacity of the existing sewer system has become grossly inadequate, calling for major improvements if the discharge of untreated sewage into the city waterways has to be prevented.
The discharge of sewage, industrial effluents, flood waters and closure of river mouths near the sea has led to the pollution of water courses, besides leaving a trail of health hazards, bad odour, mosquito breeding, and pollution of shallow aquifers.
-V S Thyagarajan
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