Connect reservoirs to stormwater drains, avoid water shortage: Experts

The four major lakes that supply water to the city contain 1,644 million cubic feet (mcft) of water which is only 14.60 per cent of its combined total storage of 11,257 mcft, as of last week.

According to data from the Chennai Metropolitan Water Supply and Sewerage Board, Poondi reservoir has only 371 mcft of water against its full capacity of 3,231 mcft, Cholavaram lake has 48 mcft against its full capacity of 1,081 mcft, Redhills lake has 1,077 mcft against 3,300 mcft and Chembarambakkam lake has 148 mcft against 3,645 mcft.

Residents and experts feel that even if the city receives less amount rainfall, if the rainwater is channelled to recharge wells and other waterbodies, it may help in reducing wastage of rainwater and helping in adding to the city’s water collection.

R Bharathi, a resident of Velachery, said, “Many lakes and temple ponds in the city are dry despite the rainfall we received this year while there are areas near lakes and ponds that were flooded. The government should divert the rainwater from the flooded areas into nearby waterbodies so that it helps in increasing the groundwater level.”

Experts feel that connecting the stormwater drains to lakes and ponds may prevent inundation. “Man-made canals can be created to let rainwater flow into lakes and ponds. The canals can be dug keeping gravity in mind so that the water can run off from high lands to low-lying ones,” Dr S Srinivasalu, the director of the Institute for Ocean Management, said.

He added that letting the surface run-off rainwater into the lakes would increase microbial content and pollution in the water bodies and the stored water can be used only after treatment. “Letting water from stormwater drains to the lake will be a solution to increase the water storage in lakes. But, we should ensure that the prevention of domestic waste from entering stormwater drains,” Dr Srinivasalu said.

He also pointed out that the rainwater could not be let underground directly through borewells, as the microbial content would pollute groundwater.

Meanwhile, with several illegal sewage lines letting wastewater into the stormwater drains in the city. The Greater Chennai Corporation has removed 361 illegal connections so far, but thousands of them continue to thrive.

An official from the Corporation said, “Last year, we checked nearly 35,000 sewage connections in the city and identified 361 illegal connections which were removed. The drive was conducted on a trial basis with Metrowater officials. We will start removing illegal connections again.”

A senior official said that the all the stormwater drains are connected to waterways and discharge the rainwater into the sea. “But, linking stormwater drains to the water bodies will be a sustainable solution. First, however, we should prevent the sewage water from entering drains and polluting the water.”

Currently, the Chennai Corporation maintains 7,360 number of stormwater drains extending over 1,894 kilometres.

KP Ramalingam, the president of Natural Water Resources Protection Movement, said, “The government should also ensure free flow of rainwater by maintaining feeder canals to the lakes. While irrigation lakes are taken care of, drainage lakes and feeder canals are encroached upon,” said opined.

The Greater Chennai Corporation has initiated the restoration of 210 tanks and lakes in the city. “We have restored 56 lakes and work on others is under way,” an official said. Even though the Chennai Corporation removes sewer inlets at the lakes, stormwater drains are not connected as they carry sewage water.