Due to monsoon deficit, reservoirs have received only half the volume of inflow
With the northeast monsoon failing to bring adequate rains to the city so far, the water resources department (WRD) is relying on the imminent increase in release of Krishna water, likely by January.
This will be a lifeline to the city and help to boost storage in the reservoirs that cater to Chennai’s drinking water needs.
The department is expecting the increase in Krishna water discharge from Andhra Pradesh to fill reservoirs with low storage.
The long-pending work to repair the damaged portion of Kandaleru-Poondi canal at Ubbalamadugu near Varadapalayam will be completed in a fortnight.
This will mean additional release of Krishna water for Chennai.
“Poondi reservoir now gets 85 cubic feet per second of Krishna water through the temporary channel. Once the work is finished, the Andhra Pradesh authorities have promised to let out a minimum of 500 cusecs to Chennai,” said a WRD official. One cusec is equal to 28.3 litres of water.
Tiruvallur district, where three of the four major reservoirs are located, has received 328 mm of rainfall, so far, this monsoon, which is deficit by 34 per cent of the average.
The four reservoirs — Poondi, Red Hills, Cholavaram and Chembarambakkam — have a storage of only 3,778 million cubic feet (mcft), much less than their capacity of 11,057 mcft.
Officials of WRD said the reservoirs usually gain an additional storage of 4,000-5,000 mcft during the northeast monsoon. But since October this year, the water bodies have received only half the volume of inflow.
Metrowater is exercising caution and drawing just 160 cusecs from the reservoirs every day, and managing with supply from other sources such as Veeranam tank and the desalination plants to supply 580-600 million litres of water (MLD) on alternate days, according to sources.
“We will need an inflow of 350 cusecs and step up storage to eventually resume daily supply of 830 MLD to Chennai,” said an official of WRD.
Sources in Metrowater said if the Poondi reservoir, the main storage unit for Krishna water, receives a steady inflow of 500 cusecs, the storage will go up by 1,200 mcft in a month.
The total storage in the reservoirs has to reach a minimum of 8,000 mcft for daily water supply to be resumed.