Mumbai, July 24 -- Modak Sagar, one of the seven lakes supplying drinking water to Mumbai, began overflowing at 2.07 am on Thursday after heavy rainfall in its catchment area, becoming the fourth reservoir to reach full capacity this monsoon. The Brihanmumbai Municipal Corporation (BMC) said one gate of the reservoir was opened after it began overflowing. Located on the Vaitarna river in Shahapur taluka of Thane district, Modak Sagar has a storage capacity of 128,925 litres and supplies about 11.2% of Mumbai's daily water requirement. It joins Vihar, Tulsi and Tansa lakes, which had already overflowed this monsoon. Vihar overflowed on July 7, followed by Tulsi later the same night, while Tansa began overflowing on Tuesday. The BMC said sustained rainfall over the past few days has significantly boosted water levels across all seven reservoirs. As of 6 am on Thursday, the lakes collectively held 1.01 million litres of water, or 69.7% of their total live storage capacity of 1.4 million litres. Built in 1954 and managed by the BMC, the Modak Sagar dam is located around 120 km from Mumbai and has a catchment area of 450 sq km....