MUMBAI: India Meteorological Department (IMD) on Wednesday retained the orange alert for Mumbai and the Mumbai Metropolitan Region (MMR), forecasting heavy to very heavy rainfall accompanied by gusty winds through the day, even as the sustained monsoon showers pushed Tansa, one of the city’s seven drinking water reservoirs, to overflow.With Tansa joining Vihar and Tulsi, three of Mumbai’s seven lakes are now overflowing, while the combined water stock across all reservoirs has touched 62% of total capacity, providing a boost to the city’s water reserves.The IMD issued an orange alert for Mumbai, Thane and Raigad for Wednesday, warning of heavy to very heavy rainfall at a few places, with strong winds of 50-60 kmph gusting up to 70 kmph.Palghar remains under a red alert, with extremely heavy rainfall likely at isolated places along with similar wind speeds.For Thursday, Mumbai and Thane have been downgraded to a yellow alert, indicating heavy rainfall at isolated places.The weather department has forecast that rainfall activity is likely to ease from Friday, with light to moderate rain expected across the region.In the 24 hours ending 8.30 am on Wednesday, the IMD’s Colaba observatory recorded 35.6 mm of rainfall, while Santacruz logged 48.4 mm.Thane recorded 88.63 mm, while Navi Mumbai received an average of 61.17 mm.The continuous rainfall over the catchment areas has led to a rapid rise in reservoir levels too.While Tansa Lake began overflowing at 8.51 am on Wednesday, it became the third reservoir to spill this monsoon after Vihar, which overflowed at 9 pm on July 7, and Tulsi, which followed at 11.43 pm the same night.According to the BMC’s Hydraulic Engineer’s Department, the combined water stock in Mumbai’s seven lakes stood at 61.90% of total storage capacity as of 6 am on Wednesday.Located in Shahapur taluka of Thane district, Tansa is one of the few masonry dams in the country.It has a maximum storage capacity of 145.08 billion litres (145,080 million litres) and contributes about 455 million litres per day (MLD), or 11%, of Mumbai’s daily water supply.Commissioned in 1892, the dam is 2,743.2 metres long, making it one of the world’s longest masonry dams.Tansa had overflowed on July 23 last year, on July 24 in 2024, July 26 in 2023, July 14 in 2022, July 22 in 2021, and August 20 in 2020, indicating that this year’s overflow is broadly in line with recent monsoon patterns.
