Even as rains are predicted to reduce over Chennai and neighbouring districts over the next few days, the Water Resources Department (WRD) plans to regulate water release from the city reservoirs until withdrawal of northeast monsoon.
The department has decided to discharge water from reservoirs to maintain a buffer space of 200-300 million cubic feet to allow some inflow during the next rain spell and controlled release into the river. “We need a gap in storage to absorb a portion of inflow and maintain the flow in the river. Once the monsoon ends, we will build storage,” said an official.
The reservoirs in Poondi and Chembarambakkam, which serve as major drinking water sources for Chennai, continued to receive inflow from the catchment areas on Tuesday. Discharge from Red Hills reservoir was decreased to 150 cusecs (cubic feet per second).
As the city reservoirs are brimming with storage after five years, Chennai Metropolitan Water Supply and Sewerage Boad (CMWSSB) is drawing nearly 560 million litres a day and has limited its drawal from other sources. This is apart from water from Veeranam tank. Chennai is now being supplied with 830 mld of water largely through pipeline.
On Tuesday, about 1,500 cusecs of water, which was received at Chembarambakkam, was released into the Adyar river. Besides its catchment area of 350 sq. km, the reservoir got flow from water bodies in Sriperumbudur, Pennalur and Irungattukottai.
Similarly, Poondi reservoir saw inflow of 5,500 cusecs and water was released into the Kosasthalaiyar river. Unlike other reservoirs, Poondi reservoir gets high flow as it has a catchment area of nearly 2,000 sq. km. in addition to the water from Ammapalli dam and the Nagari river .
Officials of the WRD said the reservoir got 460 cusecs of the Krishna water from Andhra Pradesh through Kandaleru Poondi canal. “We have informed Andhra Pradesh authorities of the copious inflow. But they are unable to control the release as waterbodies there too are full. The KP canal brought rainwater from areas enroute such as Satyavedu. Krishna water flow will reduce by half once the rains dip,” said an official.
The department plans to increase Krishna water diverted to the newly created Thervoy Kandigai Kannankottai reservoir as obstructions have been cleared.
Though 2,000 mcft of water was discharged into the Kosasthalaiyar river, only 500 mcft reached the tail-end near Sadayankuppam as major share was stored in check dams downstream. “We are diverting water to Cholavaram as it stopped getting rainwater. The five water bodies have a combined storage of 10 tmcft. now,” the official added.
Similarly, Adyar river would have carried about 3 tmcft of water since November 25. But this includes flood water joining the river in the upper stretch apart from Chembarambakkam. “This cannot be said as entirely wasted into the sea as some flow is needed to maintain the river’s ecology and moderate salinity,” the official added.
