How Do You Solve A Problem Like Flooding In Mumbai?

The story of Mumbai’s rains crippling the city is not a new one. Right from 2005, the city has come to a halt at least once a year during the monsoons. While its geography – on the coast, sandwiched between the Arabian Sea and the Western Ghats – does play an important role in this aspect, there are other factors that play their part.

By virtue of being a prominent city, Mumbai was among the first to get civic utilities including roads, underground power supply, and sewerage in place. However, this turned out to be its undoing as a lot of the city’s drainage and sewerage systems dated back to the British era, prompting the Municipal Corporation of Greater Mumbai (MCGM) to launch the Brihanmumbai Stormwater Disposal (BRIMSTOWAD) project in 1985. However, the project was delayed because of numerous reasons ranging from bureaucracy to the sheer size of the system requiring an overhaul.

A conversation with a municipal official revealed that while smaller drains usually got choked by everyday items such as bottles, plastic bags, condoms, and sanitary napkins, larger drains and the city’s four rivers – Mithi, Oshiwara, Dahisar, and Poisar – got clogged by larger object including sinks, commodes, and even sofa sets.

Many of the city’s rivers are heavily polluted, mostly by effluents from industrial and small commercial establishments. So polluted is the Mithi that the Mumbai Metropolitan Region Development Authority (MMRDA) had to begin pumping oxygen into the river in 2009. Looking to eliminate pollution at its source, the Maharashtra Pollution Control Board (MPCB) had earlier this year mandated the installation of Sewage Treatment Plants (STPs) at societies generating over 20,000 litres of sewage a day along the Mithi. Along the course of all four rivers, the city’s administrative bodies (both the MCGM and the MMRDA) have been working on widening and dredging the rivers while clearing encroachments along its banks. Getting rid of over 1,500 encroachments along the Mithi’s banks alone to widen the river and build a drainage system has been a herculean task.

Mumbai’s sewage is treated at Bandra and Worli following which the water is disposed of by two marine outfalls located 3.4km and 3.7km away respectively. However, garbage accumulation from major drains clogs up the sluice gates at the Love Grove pumping station in Worli, causing problems.

However, the major problem that the city faces is that when it rains heavily, there is also a high tide, causing the water being pumped out to get blocked.

Looking East to Solve the Water Problem

It is important to remember that the excess water is pumped westwards into the Arabian Sea and during high tides, this creates a gridlock, leaving the water nowhere to go and thus causing a flood in the city.

But what if the water was pumped out in the other direction?

Mumbai receives its rainfall from the southwest monsoon, which usually brings in heavy rainfall. Due to the island nature of the city – surrounded by sea on all sides – pumping out water towards the mainland would be a tricky solution.

For starters, water would have to be pumped across the Thane creek and then the Parsik Hills before it comes to the Western Ghats. After it crosses the ghats comes the big question: What is to be done with this water?

Carrying the water is a relatively easy task. The old Vashi bridge that is out of bounds for heavy vehicles does carry a water pipeline across it. With the Maharashtra State Road Development Corporation (MSRDC) looking to expand the new Vashi bridge, the old one can be repaired and repurposed to carry additional pipelines. Alternatively, the expansion of the second bridge can be built to accommodate the pipelines. Building pumping stations on either end of the bridge too would not be much of an issue with land from the now-abandoned Mankhurd Octroi Plaza already present. Water pipelines can also be set up on the upcoming Trans Harbour Sea Link. However, an overhaul of the drainage network to pump the water eastwards would be required.

The second part of the route – carrying the water across Navi Mumbai – can also be achieved by tunneling under the city. The MCGM had built underground water supply tunnels earlier. The Navi Mumbai Municipal Corporation (NMMC) at this stage should ideally pump in its water supply system to this as well.

To the east of Navi Mumbai lies the Parsik Hill range, following which there are plains and after which the Western Ghats begins. Tunneling under mountains to carry water has been done before. The Alva Adams Tunnel in the United States, opened in 1947, carries water from the western slopes of the Colorado River to the eastern Front Range, going right under the Rocky Mountains. The Olmos Transandino Project in Peru, when completed, will carry the waters of the Huancabamba River under the Andes, thus flowing into the Pacific Ocean instead of the Atlantic Ocean.

Closer home, water from the Mullaperiyar Dam in Kerala is channeled through a tunnel under the Western Ghats and supplied to the Vagai River in Tamil Nadu.

However, the most important question is: What is to be done with all the water?

A major reservoir would certainly be required on the leeward side of the Western Ghats. This reservoir can then store the excess water of Mumbai’s rains and the water can then be utilised for various reasons. With the twin cities of Pune and Pimpri-Chinchwad facing water shortages, the water can be used for drinking purposes. Alternatively, it can be channeled towards eastern Maharashtra, where water scarcity in the past has forced governments to send in trains of water. It is here that the current Maharashtra administration’s Jalyukt Shivar Abhiyan can play a vital role.

Perhaps it’s time Mumbai looked the other way to solve its water-logging issues. It could also help in overcoming water scarcity in other areas.