a day ago
How to explain frequent waterlogging issues plaguing Mumbai: BMC data points to spike in daily average rainfall over last 6 years
An internal analysis conducted by the Brihanmumbai Municipal Corporation (BMC) has revealed that Mumbai has experienced a significant increase in the overall amount of high-intensity rainfall over the past six years. This data was compiled by analyzing rainfall recorded by the civic body's own Automatic Weather Systems (AWS). The BMC conducted this study following the heavy rains on May 26, which were caused by an early onset of the monsoon.
According to the BMC's findings, between 2014 and 2018, on days when the city recorded heavy to very heavy rainfall, the average rainfall recorded in a single day stood at 131 mm. The study indicates that between 2019 and 2024, the daily average rainfall spiked to 182 mm, with Mumbai experiencing its highest single-day average of 267 mm on July 25, 2024. This is the most significant rainfall recorded in the last ten years.
Other notable rainfall amounts include 226 mm on July 2, 2019; 191 mm on August 5, 2020; 162 mm on July 17, 2021; and 132 mm recorded on both June 30, 2022, and July 27, 2023.
Meanwhile, during the 2014-2018 cycle, Mumbai recorded 148 mm of rainfall on September 19, 2017, making it the highest single-day average of the cycle, followed by 147 mm on July 2, 2014.
'The assessment of the internal rainfall data has also shown us that there were 28 instances in the last 10 years where we have recorded high-intensity rainfall happening within just four hours. This clearly shows that the overall quantum of rainfall is increasing, as a result of which the issues related to waterlogging continue to prevail despite intervention being taken up by us every year,' Abhijit Bangar, Additional Municipal Commissioner (Projects), told the Indian Express.
The BMC's data furthermore showed that, on average, Mumbai records rainfall above 100 mm on 16 days every year; however, the number of days has shown a marginal rise in the last three years, with 21 days recorded in 2024, 18 in 2021, and 15 in 2020. Prior to this, during the 2014-2018 cycle, Mumbai recorded 26 days of 100 mm rainfall in 2017, followed by 19 days in 2016, and 10 and 11 days each in 2014 and 2015.
Civic officials said that, as a mitigation measure, the authorities have already outlined a proposal to augment the capacity of Mumbai's drains, making them capable of handling up to 120 mm of rainfall every hour. At present, Mumbai's drains have a maximum capacity to tackle 55 mm of rainfall every hour. The augmentation of drains will lead to a smooth flow of water during heavy rainfall situations, resulting in seamless drainage.
'Alongside the overall quantum of rainfall, the population and demography of the city have also changed drastically in the past decades. The overall seasonal pattern of rainfall has also recorded a massive change in the past few years. Therefore, there is a need now to widen the existing width of the drains to improve their carrying capacity,' Bangar said.
Mumbai has an extensive drainage network consisting of 261.52 km of major nullahs (which are over 1.5 metres wide) and 411.56 km of minor nullahs (which are less than 1.5 metres wide). In addition to these, the city has other types of drains, such as arch drains and roadside drains. Overall, the total length of the drainage network in Mumbai is approximately 3,800 km.
