As the city’s reservoirs have hit rock-bottom, the dead storage is now being pumped out to sustain Chennai’s drinking water supply, indicating the intensity of the water crisis. Chennai Metrowater has started to draw dead storage from Red Hills reservoir through giant pipelines from Thursday.
Sand is now visible in the vast expanse of Red Hills lake even near the deepest point of the waterbody as the storage has dipped for want of rains for three years in a row. As drawal through gravity was not a possibility any more and running short of resources, the water agency has started tapping the minimal storage of 328 million cubic feet (mcft), which is only 10% of its capacity of 3,300 mcft.
After nearly a year, Metrowater has begun pumping 100 million litres of water a day (mld) through 750-mm dia pipelines that have been sunk up to a depth of six feet into the lake. Water drawn is being sent to treatment facilities in Kilpauk and Red Hills from where it would be distributed. “We expect the storage to last till April end in Red Hills reservoir. Evaporation loss, which is almost equal to the daily drawal is a major challenge,” said an official.
Chembarambakkam reservoir is nearly bone dry and drawal is possible only for 10 days, with the current position. Water from abandoned quarries in Sikkarayapuram would completely replace it from April. Metrowater has already started pumping 30 mld of water from Cholavaram lake too since early this week and would continue operations till mid-April.
Water from Cholavaram lake is being blended in Red Hills reservoir and then pumped for city’s water supply.
Poondi reservoir would probably be the last to be exhausted with water supply expected till May-end from there. Groundwater tapped from agricultural wells in Tiruvallur district is being kept in reserve for use in May. The water agency is confident to supply the present volume of 550 mld till May-end with these sources.
Meanwhile, the Water Resources Department has started desilting exercise in Cholavaram lake to enhance storage by 250 mcft. Nearly 38 lakh cubic metres of silt is expected to be cleared from the waterbody in the next five years.