From “intense monitoring” of filling points for water tankers to appeals for judicious use by public – the Brihanmumbai Municipal Corporation (BMC) has gone back to its drawing boards amid concerns of adequate water supply in Mumbai after the India Meteorological Department’s (IMD) latest forecast revision indicating that the country is likely to receive only 90 per cent of its long period average rainfall.The weather bureau’s downward revision has caused worry within the civic administration, with senior BMC officials on Monday convening a closed door meeting to strategise a plan for supply of adequate potable water until the summer of 2027 in Mumbai, which is entirely dependent on rain water for its daily water demands.During the meeting, the BMC administration instructed officials to closely monitor the rainfall over the lake catchment area over the next two months. “While it is too early to take any steps, the recent forecast of 90 per cent of the average rainfall is concerning as we have to ensure that Mumbai has sufficient water in its lakes till last until next monsoon season even if we do not receive rainfall in the lakes,” a senior official privy to the developments told The Indian Express.Explained | Mumbai is India’s richest city. Why does it depend entirely on rain for its water?That the El Nino weather system is associated with warmer weather conditions has further rung alarm bells among the administration.“If the lakes do not receive adequate rain and additionally the city experiences intense heat during October, it could further lead to faster evaporation of lake water. This could create a concerning situation during Summers of 2027,” an official added.As an immediate measure, the civic body is eyeing to enhance vigilance of water tankers across Mumbai’s filling points to ensure equitable and reasonable supply of water.“We are looking at intensely monitoring the water filling points as well as regulate the water tankers to ensure that the prices do not breach the normal levels as demand increases. Additionally, we are also seeking to appeal citizens to use water more judiciously and issue advisories,” sources told The Indian Express.Story continues below this adCurrently, the city is reeling under a 10 per cent water cut which came into force on May 15. While officials maintained that no decision has been taken to increase the water cut, a decision will be derived after closer monitoring of the lake levels over the next two-three months.“We will monitoring the situation over the next two – three months. Accordingly, we will decide our next course of action,” a BMC source added.Taking stock of the current forecasts, the civic body is looking an array of possibilities.“Generally, Mumbai receives adequate rain over the catchment area in the first two months with the excess rain over the next weeks flowing away. If that happens, then we may not face any difficulties even if rain is deficient from the typical normals. However, we cannot rule out the possibility of inadequate rain, which may not even full up the dams. Therefore, there is a need to be prepared for any circumstances,” said the BMC official.What makes Mumbai so rain dependentStory continues below this adMumbai draws its daily potable water from seven lakes – Upper Vaitarna, Modak Sagar, Tansa, Middle Vaitarna, Bhatsa, Vehar and Tulsi – which have a cumulative capacity of 14.47 lakh million litres.It is during the monsoon months spanning June to September that the seven lakes get replenished. Through a labryinthine network of channels, approximately 3,950 MLD of potable water from the seven lakes is then supplied across the city throughout the year.Currently, the city has no alternate source of potable water supply, making the city entirely dependent on a healthy monsoon spell.On Tuesday, the total stock in the seven lakes of Mumbai touched 15 percent or 2.21 lakh of the total capacity. With each one percent of lake stock providing water for three days, the current stock can last the city for the next 45 days.