Mumbai and Delhi which are presently reeling under water crisis will require the maximum supply of the municipal tap water in the world by 2025, according to a Mckinsey Global Institute report.
Mumbai tops the list of the 20 global cities in terms of municipal water demand in the next 13 years, followed by Delhi, the report said.
Three other Indian cities -- Kolkata, Pune and Hyderabad -- are ranked seventh, 12th and 16th respectively in the list of 20 cities needing the maximum supply.
The report is released at a time when Delhi and Mumbai are already in the grip of water crisis, especially in summer.
It said the demand would rise as urbanisation would grow fast.
"In India and China whose urbanisation is occurring on a very large scale, we are seeing the incomes of a large number of consumers hit a 'take off' level at which the consumption of many goods and services picks up speed rapidly," the report pointed out.
By 2025, the annual demand for municipal water in the world's large cities is likely to increase from around 190 billion cubic meters per year today to about 270 billion cubic meters per year.
Among the top 10 cities, Shanghai, Guangzhou, Beijing, Buenos Aires, Khartoum, Dhaka and Istanbul are other global cities that are likely to witness significant water demand.
The report further noted that building or expanding the municipal water supply infrastructure will require cumulative investment of about USD 480 billion by 2025, including investment to increase supply and to expand the distribution and treatment of wastewater.
East and South Asia will account for more than 50 per cent of this increase in water consumption, it said.