In a first, the Brihanmumbai Municipal Corporation (BMC) on Wednesday successfully carried out a controlled explosion at the Modak Sagar lake to create an opening that will help draw out additional water to tide the city over days of shortage.
The project, called lake tapping, will allow the BMC to draw water beyond the lowest drawable limit of the lake, in case the level drops drastically in case of a deficient monsoon.
The Modak Sagar lake is a reservoir created by a dam on the Vaitarana river in Thane district and caters to 11.3% of the city’s water needs. The civic body has already constructed three inlets and a new intake shaft at the lake. The inlets lead to the intake well.
The lake tapping process was carried out for the lower-most inlet [located at the 136-m level], which is located below the lakes lowest drawable limit. The controlled blast was used to throw open three-metre-thick rock plugs at the mouth of the inlet. Once the last layer of protective rock was removed, water gushed into the intake well.
The lowest drawable limit of the Modak Sagar lake is 143m. With the lake tapping process successfully completed, the BMC can draw the water till the 139-m mark, four metres below the lowest drawable limit. This will give the city roughly 30,000 million litres of water – which amounts to about eight days’ supply.
About 180 kg explosives were used in the blast, which was triggered by Shiv Sena chief Uddhav Thackeray at 1pm. The process a collaboration between the state’s water resource department and the BMC’s hydraulic department. “We are first civic body in country to carry out lake tapping. I applaud the engineers involved,” Thackeray said.
Civic chief Sitaram Kunte said, “The method prepares us in case there is deficient monsoon and allows us to draw water below the lowest drawable limit.”
Lake tapping has been earlier carried out twice in Koyna hydro-electric reservoir by Maharashtra government to facilitate generation of power even when the water level goes down in peak summer.