Mumbai: Water stock trails previous years as BMC plans for possible shortage

Vihar Lake in Mumbai, one of the seven lakes supplying water to the city. File pic

Mumbai's seven lakes have a cumulative water stock of 90.48 per cent of their total capacity - about six percentage points lower than at the same time last year and nearly seven percentage points lower than in 2024. With drought conditions prevailing in parts of Maharashtra, the state government has advised civic bodies to adopt water-saving measures, including planning for water availability until August 31, 2027.

The Brihanmumbai Municipal Corporation (BMC) has already announced a 10 per cent water cut. However, civic officials say the city's existing reserves are unlikely to last until August 31, 2027, even if the cut is sustained. According to BMC calculations, the current stock could last until May 21, 2027, if the city continues receiving its regular supply of 4100 million litres daily (MLD). If the 10 per cent cut is maintained, the reserves could stretch until June 14.

mid-day's analysis indicates that Mumbai could need up to 510 billion litres of additional water from the state government if the cut is not sustained, and up to 351 billion litres even if the 10 per cent cut continues. These estimates cover the period during which the city would need additional supplies to bridge the gap until August 31, assuming there is no replenishment from rainfall.

Civic officials said the BMC generally seeks reserved water from the state when lake levels fall to around 7 per cent, a threshold that could be reached around May 2027 if conditions do not improve.

"We draw limited quantities of water daily to meet the city's supply requirements until the rains arrive. The BMC pays the state government for this water," a civic official said, adding that the corporation drew 2.27 lakh million litres (ML) of reserve water from the state in 2026.

The BMC is hoping that rainfall arrives earlier than expected, easing concerns over a possible delay associated with El Niño. Otherwise, the civic body may have to seek substantially more reserve water from the state in 2027 than it did this year.

An increase in the existing water cut is not being considered for now. Officials said maintaining even the announced 10 per cent cut becomes difficult during periods of higher demand, including the festive season in September and October, when temperatures also remain high.

A senior civic official said the corporation would prefer to avoid further cuts and expects the state to provide reserve water as it has in previous years. Another official acknowledged that the BMC could not be certain how much additional water the state would sanction. "Although we are hopeful of atleast 2.27 lakh ML" the official said.

mid-day's analysis: The additional water Mumbai may need

Civic officials said increased demand during the festive season and the October heat often makes it difficult to sustain water cuts. With summer still ahead, the city could face a significant supply gap if the 10 per cent cut is not maintained.

If the cut is not sustained

If existing stocks last until May 21, 2027, Mumbai would need additional supplies for 102 days, until August 31. At a requirement of 5000 MLD (as per officials), the city could need up to 510 billion litres of additional water.

If 10% cut is sustained

If existing stocks last until June 14, 2027, Mumbai would need additional supplies for another 78 days to bridge the gap until Aug 31. At a requirement of 4500 MLD, this would amount to up to 351 billion litres.

When could Mumbai run short?

According to BMC calculations:

>> Without a water cut: Existing stock could last until May 21, 2027.
>> With a sustained 10% cut: Stock could last until June 14, 2027.
>> With reserve water, without a sustained cut: Stock could last until June 22, 2027.
>> With reserve water and a sustained 10% cut: Stock could last until July 20, 2027.

Official Speak

Senior civic official,
‘No additional water cut is being considered for now. We would also like to avoid that in the future. The state would provide us with the required reserve water, as it does every year. We do not expect drought conditions in other parts of the state to influence the state's decision to provide us with water, because these catchments cannot serve those areas anyway'

Civic official,
‘We will have to seek substantially more reserve water in 2027 than this year. We cannot say whether the state will provide it or not. Early rainfall, instead of the expected delay, could ease the situation. Further increasing water cuts is a difficult choice that we may consider'

How Mumbai gets its water

According to civic officials, Mumbai draws water from seven lakes through two systems. The Vaitarna system, comprising Upper Vaitarna, Modak Sagar, Tansa and Middle Vaitarna, supplies the western suburbs and parts of the city. The Bhatsa system, along with Vihar and Tulsi lakes, supplies the eastern suburbs and other areas.

In 2026, the BMC drew around 1.37 lakh million litres (ML) of reserve water for Bhatsa and 90,000 ML for Upper Vaitarna, taking the total to 2.27 lakh ML, up from 2.10 lakh ML in 2025. A senior civic official said, "We expect Upper Vaitarna will need more reserves" in 2027.

1,309,541 ML
Current lake stock

1,447,363 ML
Total capacity

90.48%
Current stock: as of October 18, 2026

96.62%
Stock on October 18, 2025

97.14%
Stock on October 18, 2024

250 MLD
Ongoing water loss to evaporation

4100 MLD
Regular water supply