If you ask those who grew up in Mumbai in the 80s what they associate with Vihar Lake, most likely they will say the Humpty Dumpty statue and the annual school picnic on the lake’s banks. Vihar and six other artificial lakes, built over the past two centuries, still meet the majority of Mumbai’s water demand.
According to the Brihanmumbai Municipal Corporation (BMC), which undertakes the humongous task of water provision to the city, its water supply system is the largest in Asia. BMC distributes around 4,000 million litres of water per day (MLD) to over three million Mumbaikars. Yet, many citizens face a water shortage.
Until the mid-19th century, Mumbai depended on wells and tanks for water, according to the Gazetteer of Bombay Island and City. But its burgeoning population led to a commensurate increase in the demand for water. Besides, the wells, built in crowded areas, were susceptible to pollution, a problem compounded by water shortage.
Around 1845, water shortage forced the government to appoint a committee to augment supply. This resulted in the creation of Vihar lake, the first of the seven lakes that supply water to Mumbai.
Water sourced entirely from lakes
Here are the seven lakes that meet Mumbai’s water needs today.
- Vihar lake
By 1860, Vihar lake was created by building a dam at the source of Mithi river. Today it lies within the Sanjay Gandhi National Park, and contributes 90 MLD (2%) to Mumbai’s total supply of 4000 MLD. Its total holding capacity is 27 billion litres.
- Tulsi lake
After a commission recommended augmenting the supply from Vihar lake, the government, in 1872, built a dam across the Tassu river located below a village named Tulsi. Initially an auxiliary to Vihar lake, it was made an independent reservoir in 1877 by linking it directly to the city. Tulsi lake is also located in Sanjay Gandhi National Park and is the smallest of the seven lakes. It supplies 18 MLD of water to the city, and has total capacity of 8 billion litres.
- Tansa lake
Located in Shahapur in Thane, Tansa lake supplies 455 MLD water to Mumbai. Its construction started in 1886, but was completed in four stages by 1945. Its capacity is 145 billion litres.
- Lower Vaitarna lake
As Mumbai’s water demand rose due to its increasing population and industrialisation post independence, the municipal administration built a dam in 1954 on Vaitarna river that originates in Nashik district. It was named Lower Vaitarna, or Modak Sagar after N V Modak, the municipal corporation’s chief engineer at the time. It supplies 455 MLD water, and has total capacity of 129 billion litres.
- Upper Vaitarna lake
In 1960, the state government developed the Upper Vaitarna multipurpose scheme by building two dams across Vaitarna and Alwandi rivers. The water is used for generating electricity and then let off into Modak Sagar lake for supply to the city. Upper Vaitarna lake supplies 640 MLD to Mumbai, and has storage capacity of 227 billion litres.
- Bhatsa lake
Maharashtra government built the multipupose Bhatsa dam in 2005 in Thane district on the confluence of Bhatsa and Chorana rivers. The largest of the seven lakes, it supplies 2020 MLD water and has total capacity of 717 billion litres.
- Middle Vaitarna lake
BMC built the newest dam in 2014 on Vaitarna river in Thane district. Middle Vaitarna is the third largest dam in Maharashtra, supplying 455 MLD to Mumbai. Its total capacity is 193 billion litres.
Bhatsa and Upper Vaitarna lakes are under the state government’s jurisdiction, and the other five are under BMC. Other than Mumbai, these lakes also supply water to Thane and Bhiwandi municipalities and to some villages.
Two supply systems cover the whole city
The water from the lakes is purified at two treatment plants, and then brought to 27 reservoirs in Mumbai. From there the corporation supplies water to citizens.
According to an official from BMC’s Hydraulic Engineering Department, the Lower, Middle and Upper Vaitarna lakes, along with the Tansa lake, make up the Mumbai 1 system. The water from this line is purified at the Bhandup Water Treatment Plant. It is then supplied to the western suburbs from Dahisar Check Naka to Bandra, and to the western part of the city from Mahim to Malabar Hill.
Read more: Rainwater harvesting: Why don’t Mumbai societies do enough?
Bhatsa, Vihar and Tulsi lakes constitute the Bhatsa system or the Mumbai 2 line. After purification at the Panjarpur Water Treatment Plant, water is sent to the eastern parts of the city and the eastern suburbs – from Mulund Check Naka to Sion, and from Sion to Mazgaon.
More demand than supply?
The city consumes only 12% of lake water every month, but factors like evaporation and low percolation could cause shortage, a senior BMC official said. To ensure water lasts till July 31st, BMC takes a call on whether to impose water cuts in the summer. Last year, for instance, BMC implemented a 5-10% water cut in May and June.
However, thousands of residents face water shortage even in the non-summer months. Citizen Matters has covered how people living in informal settlements struggle to access water as well.
Sitaram Shelar of Pani Haq Samiti, an organisation campaigning for universal access to water, says the corporation’s figures on the demand-supply gap keeps changing. “This is generally a made-up gap. If you ask the BMC for data to support it, they won’t give you any data.” He also says that according to the BMC, 30% of water brought to the city’s reservoirs is lost due to technical factors, leakage and theft, but the corporation is not ready to explain how they arrived at this figure.
Read more: How water crisis deepens gender inequality
Environmental anthropologist Nikhil Anand in his book Hydraulic City: Water and the Infrastructures of Citizenship in Mumbai, talks about a manufactured narrative of scarcity: “In fact, scarcity narratives around Bombay/Mumbai’s water systems have been remarkably consistent throughout the colonial and postcolonial period.” He explains that “scarcity talk” enables the water department to justify getting more water from rural rivers. It also allows them to control water pressure, ration water, and prioritise the needs of some over others.
Nikhil says over a phone call, “The city has grown in ways that the water infrastructure has not kept up with. This is one of the reasons why relatively newer neighbourhoods like Malad, Mankhurd receive less water.”
Sitaram says BMC has not responded to activists’ demand for a water audit even as BMC engineers train other Asian cities on conducting audits.
Poor utilisation of sustainable water sources
Activists say that Mumbai’s groundwater is also getting drawn at an alarming pace for construction projects. Some societies also dig borewells to extract water for non-drinking purposes like flushing and gardening. Changing rainfall patterns and the increasing concretisation of the city impact water percolation into the ground as well. Because of depleting groundwater levels, housing societies and commercial establishments now need NOCs for extraction from the Central Ground Water Authority.
Read more: How changes in central rules for groundwater management are affecting Mumbaikars
While there is a clamour for water every year, BMC continues to rely on lakes and has not sufficiently utilised sustainable sources like rainwater or recycled wastewater.
Fortunately, Mumbai is set to get seven STPs over the next couple of years.
According to the regulations of BMC’s Building Proposal Department, any new property built over 500 sqm must mandatorily have a rainwater harvesting system, without which they wouldn’t receive an occupancy certificate (OC). Though societies do set up RWH systems to get OC, the implementation leaves much to be desired.
Instead of utilising these alternatives, a new dam on the Gargai river is in the works, pending permission from the Forest Department. The Gargai dam project has already come under fire from environmentalists who point out that it would lead to massive deforestation.
Also read:
- Rainwater harvesting at Oval Maidan: Lessons for the rest of Mumbai
- Water shortage in Dombivli has only worsened with time, exacerbated by rapid urbanisation, poor water management and erratic monsoons.
- Water shortage in Bengaluru: Families, schools, hospitals share their struggle