While the monsoon rains cause widespread waterlogging, floods and crippling of daily life in Mumbai each year, the dense grey clouds do bring a silver lining. The rains replenish the seven reservoirs that supply drinking water to over 13 million people across the metropolitan. The city's water security depends almost entirely on how much rain these lakes receive during the southwest monsoon, making reservoir levels one of the most closely watched indicators every rainy season.
Mumbai draws nearly all of its drinking water from seven reservoirs located across the Mumbai Metropolitan Region and neighbouring districts. While the BMC manages the city's treatment and distribution network, several of the dams are owned and operated by the Maharashtra government's Water Resources Department. Together, the reservoirs have a live storage capacity of 1.447 trillion litres, enough to sustain the city through the dry months until the next monsoon.
Why Monsoon is crucial
Unlike many Indian cities that depend on rivers or groundwater throughout the year, Mumbai stores almost its entire annual water requirement during the four-month southwest monsoon. If rainfall is deficient or delayed, reservoir levels fall rapidly, often forcing the BMC to impose water cuts and conservation measures.
The 2026 monsoon highlighted this dependence. Following one of the driest Junes in more than a decade, reservoir storage had dropped to critically low levels, prompting the BMC to introduce water conservation measures and restrict supplies to certain commercial users. However, sustained heavy rainfall during early July significantly improved the situation, replenishing the reservoirs within days.
Who manages Mumbai's water?
Mumbai's water supply system is managed by multiple agencies.
The Brihanmumbai Municipal Corporation's Hydraulic Engineer's Department is responsible for treating and distributing drinking water across the city. It also monitors daily reservoir levels and operates the extensive network of treatment plants, pipelines and service reservoirs.
The Maharashtra Water Resources Department owns and manages key reservoirs such as Bhatsa and Upper Vaitarna, while coordinating dam operations during the monsoon.
At the national level, the Central Water Commission monitors hydrology, reservoir storage and flood situations but does not directly operate Mumbai's reservoirs.
Reservoirs from which Mumbai gets its water supply
Mumbai's drinking water comes from seven reservoirs -- Bhatsa, Upper Vaitarna, Middle Vaitarna, Tansa, Modak Sagar, Vehar and Tulsi.
Bhatsa is the largest source, with a storage capacity of 717,037 million litres, accounting for nearly half of Mumbai's total water storage. It is owned by the Maharashtra government and is the single biggest contributor to the city's daily supply.
Upper Vaitarna, another Maharashtra government reservoir, can store 227,047 million litres and forms a major part of Mumbai's western water supply system.
Among BMC-owned reservoirs, Middle Vaitarna has a capacity of 193,530 million litres, followed by Tansa with 145,080 million litres and Modak Sagar with 128,925 million litres.
Vehar and Tulsi, located within Mumbai inside the Sanjay Gandhi National Park, are the smallest reservoirs, with capacities of 27,698 million litres and 8,046 million litres respectively. Though relatively small, they provide an important supplementary source of water and are often among the first reservoirs to overflow during a good monsoon.
Current water levels at these reservoirs after July rains
Following heavy rainfall during the first week of July, reservoir storage improved significantly.
- Bhatsa currently holds around 306,002 million litres, or 42.68 per cent of its capacity.
- Upper Vaitarna has 61,028 million litres, or 26.88 per cent.
- Middle Vaitarna stores 81,508 million litres, representing 42.12 per cent of capacity.
- Tansa has reached 112,413 million litres, or 77.48 per cent.
- Modak Sagar is holding 106,566 million litres, or 82.66 per cent of its storage.
- Vehar and Tulsi have both reached full capacity and are at 100 per cent storage.
Summed up, the seven reservoirs now hold around 703,260 million litres of water, nearly 49 per cent of their total live storage capacity.
Supply areas
Unlike many cities where individual reservoirs supply specific localities, Mumbai's water system functions as an integrated network.
Water from multiple reservoirs is transported through interconnected pipelines before being treated at the Bhandup and Panjrapur water treatment plants. It is then distributed through a network of master balancing reservoirs and 27 service reservoirs across the city.
As a result, no single reservoir serves only one neighbourhood. Instead, the combined storage from all seven reservoirs supplies drinking water to the entire BMC area, including South Mumbai, the eastern and western suburbs, and parts of the extended metropolitan region.
How much water do Mumbai residents get
The BMC currently supplies around 4,000 million litres of treated water every day to more than 13 million residents.
With rapid urbanisation and population growth, demand is expected to rise substantially in the coming years. Official projections estimate Mumbai's daily water requirement could reach about 6,535 million litres by 2041, leading to the development of new projects such as the Gargai Dam, the Pinjal Dam and the Damanganga-Pinjal River Link.
Why reservoir levels are watched every monsoon
Every year, the BMC publishes daily updates on the seven reservoirs because they determine whether Mumbai will have sufficient water until the following monsoon.
A weak monsoon can force civic authorities to introduce phased water cuts, while abundant rainfall helps replenish storage early, ensuring uninterrupted supply throughout the year.
