Mumbaiis losing about 1,500 to 2,000 million litres of water per day (MLD) because of evaporation.

Mumbai gets water from six lakes in Thane district. Every day, the civic body supplies 3,250 MLD to the city, though the requirement is about 4,250 MLD. Against the supply, water content in the lakes is depleting by around 5,000 MLD.

For instance, according to the BMC’s data, the water quantity in all six lakes was 9,64,910 million litres on December 20. On December 21, the content was 9,60,116 million litres. This shows that the content went down by 4,794 million litres in one day.

Officials of the hydraulic department agreed that the water content is going down because of evaporation, but it is not the sole reason. “The BMC also supplies about 150 MLD to Bhiwandi, about 100 MLD to Thane city and also some water to villages around lakes in Thane district,” said an official.

“The rate of evaporation is a bit higher during winter than in summer, as humidity is low in this season,” said the official.

The BMC had earlier mooted a proposal to reduce evaporation from lakes by adopting a method from Singapore. It involved spreading a thin film of a potable, oil-based liquid over the water surface to reduce the penetration of sunrays into the lakes. But a study proved it would be harmful to the lakes’ underwater ecology.