Rain brings very little inflow into city reservoirs

With the combined storage of four reservoirs now at 305 mcft, Metrowater has resumed drawal from two waterbodies for city supply

CHENNAI, 08/06/2017 : For City : The second largest water supply of the metropolis of Chennai is drawn from Chembarambakkam lake,once known as Puliyur, which is a major water source for Chennai. which existed even during the later Chola period in Thondai Mandalam which had Kanchipuram as its headquarters. The Full Tank Level is 85.40 ft (26.03 m). The lake is almost dry and have supply only for the few more days. Chennai requires a regular supply of 831 million litres per day (MLD). The water level has dropped alarmingly down even before the beginning of the summer. Photo: B. Jothi Ramalingam

Despite intermittent rain in the city in August, storage in the lakes has not improved significantly. However, this was enough for Chennai Metrowater to resume drawal from two waterbodies for water supply.

On Thursday morning too, the reservoirs recorded moderate rainfall. The Poondi reservoir received 41 mm, which is the highest volume among the reservoirs. Chembarambakkam too received 29 mm of rainfall. The consistent rain over the past month has boosted some storage in the lakes that went completely dry.

Though it rained for several days in August, it did not translate entirely into inflow into the reservoirs. Unlike the intense rainfall that covers a widespread area during the Northeast monsoon, thundershowers during Southwest monsoon is not uniform and brings short spells of rain, said weather experts.

Officials of the Water Resources Department said the runoff from catchment areas would be limited as not all areas upstream of reservoirs would have got rainfall. Moreover, percolation of rainwater would be more during these months particularly after a prolonged dry spell.

“Instead of flowing into the reservoir, rainwater collected in the catchment areas would infiltrate into the ground. The rain now would help boost the water level in the ensuing Northeast monsoon,” an official said.

The combined storage of the four reservoirs now stands at 305 million cubic feet against its capacity of 11,057 mcft. The waterbodies in Cholavaram and Red Hills that remained bone dry till mid-August now have 22 mcft and 79 mcft of water. While it is grossly lower than the capacity, the available resources are being drawn for city supply.

Officials of the Metrowater said about 50 million litres a day (mld) is being drawn from Red Hills and Chembarambakkam reservoirs for the past two days. This has helped augment the city’s water supply in a small way. At present, the water agency is supplying about 470 mld to Chennai, mostly through tanker trips.

However, this may not last long and more rainy days are needed to build the storage. As Veeranam tank remains dry, the water agency is drawing about 100 mld of water from well fields in Paravanar river belt, officials added. With these available sources, the water agency hopes to manage the water supply till onset of the Northeast monsoon.