In 1999, planners estimated the population growth in the city to be saturated around 158 lakh by 2020-21. With a demand of 240 litres per capita per day (lpcd), it was projected that the city would require about 5,300 million litres per day (MLD).
But the good news is that the 2011 Census has shown that the projected growth in 2020-21 has come down to around 130-135 lakh. Accordingly, the demand of water will be around 4,000 MLD, instead of 5,300.
Besides, slum redevelopment projects and reconstruction of old buildings have not taken off as expected. Hence, demand from slums and old buildings will remain around 100-120 lpcd only.
They constitute 60% of Mumbai (50% in slum and 10% in old buildings). The real demand will be around 3,500 MLD. In other words, Mumbai will have sufficient water (present supply 3,400 MLD) and adequate storage. In spite of all this ,24X7 water supply is still a distant dream.
Problems plaguing the 24X7 dream is unprecedented and unequal growth and the steady growth in demand.
From 1960 onwards, Mumbai has been growing at a very rapid rate. What was 28 lakh in 1960 is 119 lakh in 2001. City planners had forecast that it will stabilise around 158 lakh in 2021. The 2011 Census shows that growth has fallen considerably. The population was expected to be 138 lakh in 2011, but it has turned out to be 125 lakh. Western suburbs have grown at a much faster rate than eastern suburbs.
According to a survey carried out by the hydraulic department, in 1980, 120 to 135 (lpcd) was an adequate quantity. It shot up to 240 lpcd in 2001. This is due to improved living standards of citizen, coupled with the use of modern gadgets in bathrooms and toilets.
Even in slums, water demand has grown from 50 lpcd to 100 lpcd.
All new buildings have suction tanks, pumps and overhead tanks.
More and more buildings are coming with suction tanks. They have inlets located within 600mm height from ground. As water finds its own level, it brings down the pressure in the distribution system. This will lead to short supply in old buildings as there are no suction tanks.
Now, with the redevelopment policy of old buildings and slums in place, more and more new buildings are coming up with suction pipes in the same localities, bringing down water pressure further. This will lead to total inequality in the distribution of water supply.
There is no solution to this problem, unless all different supply systems, one with high pressure and one with low pressure, are laid side by side. It’s a near impossible task, given the financial and space constraints. Citizen will have to wait till total redevelopment of Mumbai is carried out.