Mumbai: Mumbai's water security is facing fresh concerns as storage in the seven lakes supplying the city has fallen sharply within weeks of the southwest monsoon's withdrawal. From nearly 97% of their combined capacity in late September, the reservoirs' stock has plunged to 80.54% as of November 13, with a rain-free October, rising temperatures and continuous withdrawals for daily consumption accelerating the depletion.
The seven lakes held 11.65 lakh million litres on November 13, significantly below the 13.52 lakh million litres (93.43%) recorded on the corresponding date last year and 13.02 lakh million litres (89.99%) in 2024. More significantly, the last time Mumbai recorded a lower storage level on this date was in 2018, when the reservoirs held 79.63% of their capacity. The drop from approximately 14.05 lakh million litres in late September also highlights the pace at which the city's reserves have depleted in just over a month.
Adding to the concern, BMC's October evaporation assessment of Tansa, Modak Sagar and Middle Vaitarna revealed a substantial increase in water losses compared with the same period last year. At Tansa, evaporation more than doubled to 1,729.01 million litres from 823.53 million litres. Modak Sagar recorded losses of 1,299.60 million litres, against 644.84 million litres, while Middle Vaitarna witnessed an even sharper rise from 381.34 million litres to 1,018.42 million litres.
The declining storage is equally evident in individual reservoirs. Tansa was holding just 81% of its capacity against 95.92% last year, while Middle Vaitarna stood at 86.56%, compared with 99.53%. Modak Sagar's storage had slipped to around 50%. "Inadequate rainfall during three monsoon months, unusually high October temperatures and the early withdrawal of the monsoon have further restricted inflows," said a senior civic official.
Water Demand vs Supply: 4,600 MLD demand against 4,100 MLD supply, leaving a 500 MLD shortfall.
Non-Revenue Water: Around 34% of daily water supply, including losses from leakages, illegal connections and water theft, according to the BMC. As per sources 16-17 % is leakages.
According to BMC projections, the stock could last until June 10, 2027, without a water cut or retention of reserve storage, and until September 5, 2027, if the existing 10% cut continues and approved reserves in Upper Vaitarna and Bhatsa are maintained.
Water stock as on November 13....
Lakes.....current level(mtrs) ....Full level (mtrs)...useful content (ML)
Upper Vaitarna..602.93....603.51....208724
Modak Sagar....154.28......163.15...61530
Tansa...126.84......128.54...111924
Middle Vaitarna....277.94...285...152210
Bhatsa...137.66......142.07....599879
Vehar...79.56.....80.12....24776
Tulsi...138.17....139.17...6725
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