India: Mumbai Water Supply Levels Decline for a Third Year

29 July 2020 Mervyn Piesse, Research Manager, Global Food and Water Crises Research Programme

Background

Mumbai, a city of 20 million on the west coast of India, often experiences considerable water supply challenges, especially in the month before the start of the annual monsoon. At the end of June 2019, the city’s water supply was barely enough to meet demand for a month. A water shortage in the business, banking and financial capital of India would have devastating consequences for the country. While the city’s slums face constant water supply challenges, a severe water shortage in the city will only make it more difficult to combat the spread of Covid-19.

Comment

The city’s water is mainly sourced from seven lakes – Bhatsa, Tansa, Upper Vaitarna, Middle Vaitarna, Modak Sagar, Tulsi and Vihar. In late July 2020 (part way through the annual monsoon season) the city only had enough water to meet demand for 109 days. Collectively, the lakes have 50 per cent less water than they did in July 2019. Bhatsa Dam, which supplies more than half of the water used in Mumbai, is only one-third full. Tulsi Lake recently filled beyond its capacity but, as it supplies only about one per cent of the city’s water, it is not going to markedly improve the water supply situation.

The south-west monsoon occurs from June to September and accounts for 75-90 per cent of the annual rainfall in western India. The city’s water supply agency is confident that water restrictions will not need to be imposed, as most of the monsoonal rain falls in July and August. If the rains are below average over that time, however, there is a very strong chance that water use restrictions will have to be enacted.

While the city itself has recently received large amounts of rain, inflow into the lakes remained low. Only one-third of the required rainfall has fallen into the catchments so far this monsoon season. At the same time last year, 70 per cent of the required rainfall had entered the city’s lakes.

A lack of water and inadequate sanitation will make it difficult to contain outbreaks of Covid-19 in India. Mumbai has the largest share of slum dwellers of any Indian city and the largest slum in India, Dharavi, is located within its boundaries. An investigation, conducted by city authorities, found that more than half of the people living in Mumbai’s slums have had the virus. Without adequate water supplies, however, it is possible that the virus will spread into more affluent parts of the city as well.

Mumbai relies on the annual monsoon to replenish its surface water sources. If the lake catchments do not receive adequate levels of rainfall over the next two months, it is likely that the city will face considerable water supply challenges over the next 12 months.

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