How July rains saved Mumbai from a water crisis: A data-driven look
Mumbai, a coastal city of over 20 million people, relies on just seven reservoirs for its year-round water supply. After a delayed monsoon onset and fears of El Niño-driven shortages, heavy July rains have pushed lake levels to a three-year high. As of July 28, combined useful water storage stood at 88.81 percent of total capacity — a sharp recovery from the 72.97 percent recorded on the same date in 2024, and slightly above the 88.70 percent seen in 2025.
This turnaround offers a case study in how climate variability and infrastructure resilience interact, with lessons for water-scarce regions globally.
How did Mumbai’s water supply get to this point?
Mumbai draws water from seven lakes: Tulsi, Vihar, Bhatsa, Tansa, Modak Sagar, Upper Vaitarna, and Middle Vaitarna. These reservoirs are spread across suburban Mumbai and the neighboring districts of Thane, Palghar, and Nashik. In May, when water stocks fell below 25 percent of capacity, the Brihanmumbai Municipal Corporation (BMC) imposed water cuts. The India Meteorological Department (IMD) had forecast below-normal monsoon rainfall due to the El Niño phenomenon — a natural climate pattern that suppresses rainfall over the Indian subcontinent by warming ocean surface waters and weakening trade winds in the central and eastern tropical Pacific.
The monsoon typically arrives in Mumbai by the first week of June, but this year it was delayed until June 30. However, July delivered an extraordinary 1,490 mm of rainfall at the IMD’s Santacruz observatory, far exceeding the monthly average of 919 mm. This deluge rapidly refilled the reservoirs.
Which lakes are full, and which still need rain?
According to BMC data, four of the seven lakes — Tulsi, Vihar, Modak Sagar, and Tansa — have reached 100 percent useful capacity. Middle Vaitarna stands at 90.3 percent, Bhatsa at 87.36 percent, and Upper Vaitarna at 77.51 percent. In the 24 hours ending Tuesday morning, Upper Vaitarna received 85 mm of rain, followed by 72 mm at Bhatsa and 57 mm at Modak Sagar.
Despite the recovery, the BMC supplies 3,850 million liters daily (MLD) against an estimated demand of 4,300 MLD — a deficit of 450 MLD. Civic officials have stated that water cuts will remain in place until total stocks reach 100 percent capacity, which typically happens by the end of September.
What does the forecast look like?
Rainfall over Mumbai has eased temporarily. Between Monday and Tuesday morning, the eastern suburbs received 19.39 mm, the island city 10.82 mm, and the western suburbs 10.68 mm. The IMD predicts light to moderate rain for the city and suburbs on Tuesday. The BMC also warned of two high tides: 4.01 meters at 11:45 am and 3.5 meters at 11:30 pm.
Rain activity is expected to pick up closer to the weekend. The IMD has issued a new yellow alert for Mumbai, Thane, and Palghar starting Friday, warning of thunderstorms, lightning, moderate rainfall, and gusty winds of 40 to 50 km per hour.
FAQ: Mumbai’s water supply and climate risks
Why does Mumbai depend on just seven lakes?
Mumbai is an island city with limited groundwater and no major rivers. Its water supply system was built in the 19th and 20th centuries, relying on reservoirs in the surrounding hills. Expanding the system is costly and politically complex.
How does El Niño affect Mumbai’s monsoon?
El Niño typically suppresses rainfall over the Indian subcontinent by altering atmospheric circulation. This can delay the monsoon onset and reduce total precipitation, as seen in May and June this year.
Will water cuts end soon?
Not immediately. The BMC will keep cuts in place until all seven lakes reach 100 percent capacity, which usually occurs by late September. Even then, the city faces a structural deficit of 450 MLD between supply and demand.
What can other water-scarce cities learn from Mumbai?
Mumbai’s experience highlights the importance of diversified water sources, real-time monitoring, and adaptive management. The city’s ability to recover from a near-crisis in May to a three-year high in July shows that even vulnerable systems can bounce back with timely rainfall. But the structural deficit — 450 MLD — underscores the need for long-term investments in water conservation, desalination, and demand management.