On any given day, 4173 million litres (MLD) of water flows towards Mumbai. It travels through 650 km of transmission pipes and 6000 km of service pipes, to eventually provide just 2300 million litres for its residents. The difference — 1,900 MLD — is lost due to a variety of reasons, including leakage, thefts, dysfunctional or rigged water meters and non-metered municipal connections.
7.74% – 323 MLD – is lost before the water is even made fit for drinking, en route to the two water treatment facilities at Bhandup and Panjrapor, northeast of the city. These are conveyance losses, and seepage due to pipe imperfections and environmental factors like evaporation contribute to it.
Of the remaining 3,850 MLD, another 1550 MLD is lost from Brihanmumbai Municipal Corporation (BMC)’s network. Tricky to quantify or bill, this is referred to as Non-Revenue Water (NRW) or Unaccounted-for Water (UfW). According to the BMC’s own figures, from 20% in 2009 to 27% in 2018 and 22% in 2019, it reached 40.22% in 2020.
“The amount of water billed fluctuates depending on supply, so there is some scope for error,” says an executive engineer in the hydraulic department of the MCGM.
From preventing water leaks to repair to replacing pipes
“Mumbai’s pipe network is almost 100 years old, and was built for a third of the population present today,” says Subhajit Mukherjee, a consultant appointed as a ‘Jal Rakshak’ for his work in water conservation for Jal Shakti Abhiyaan. Wear and tear and rust-induced disintegration are inevitable. These are not always evident, especially in larger-diameter pipes buried deep underground.
“Left unattended for years, they eat away at the earth and eventually cause random and chaotic sinkholes,” writes Nikhil Anand in his book, Hydraulic City: Water and the Infrastructures of Citizenship in Mumbai. As the largely reclaimed terrain is hollowed out, we see instances like the drowning of a parked car that went viral in June 2021.
Comparatively, leakage in shallow pipes, often installed without following standard guidelines, to cut costs, is easily noticeable. The effects are visible on the ground or in the output from taps. But the depth is often to blame for the damage, as the pipes buckle under the impact of vehicles, road works, and construction activity.
The BMC claims they fixed 1.73 lakh leaks in the past few years, which is a significant number. Yet the city has all but stopped proactive detection of these leaks.
Leak detection squads have a small history, being in operation from 1972 to 2002. Pressure from Pani Haq Samiti (PHS), a water rights group, led them to get reinstated, but they were not very effective. They were, once again, disbanded in 2018.
“The objective shifted from leak detection and prevention to leak repair, which is a lot more lucrative,” says Sitaram Shelar, co-founder of PHS. The BMC now assigns ward-level contractors to temporarily fix leaks.
Detecting water leaks in the pipelines
The challenges to leak detection, however, run deep and are systemic. For starters, maps are incomplete. “While Mumbai has one of the better-documented systems, a lot more information is with local labourers than the MCGM,” says Asim Bhalero. Asim is the co-founder of Fluid Robotics, a company tackling water and waste-water problems in developing countries.
Barely 6 inches in height, the company’s in-pipe robot uses AI and sensors and can crawl, float, and swim through pipes. It maps and inspects them as it travels through, checking for leaks and structural health. The BMC and other Municipal Corporations have contracted Fluid Robotics to do so in the past. But hurdles arise when it comes to the smaller-diameter pipes that make up the water distribution system.
“A lot of pipes don’t have any access points, which are valves that can be controlled from above ground,” says Asim. Locating the pipes, digging and breaking them to let the robot run for a few hours, and sealing it in step with water timings has proved to be a challenge. External detection technology, like sounding rods, is preferred, but becomes prohibitively expensive according to Asim, especially for pipes past their prime.
Pressure monitors can be attached to pipes to give alerts of sudden drops in pressure. But, as Hydraulic City reveals, they fluctuate wildly due to the intermittent water flow schedule, and eventually break down
“When water leaks, there’s a high chance it ends up getting into a local aquifer and back into the water cycle, which could be why curbing it has been neglected,” says Asim. It will improve, he supposes, with the push towards a 24×7 water supply system.
Water leaks form bulk of complaints
A partial substitute for official vigilance is found in citizens’ complaints. Praja’s report on Status of Civic Issues in Mumbai, 2021 tabulated BMC complaints: In 2020, the BMC received 11,855 complaints related to water, of which 29% (3,434) were about leaks. Complaints about quality, 12% (1,369), and shortage, 30% (3,914), can also be a giveaway of a leak in the vicinity.
“A leaky sewage line, soil, or seawater can contaminate water reaching homes and based on the extent, can point to the leak,” says Subhajit Mukherjee.
Once alerted, the BMC’s engineers or private contractors pinpoint the bleed using a mix of old and new technology. The most common method uses helium gas, injecting it into a cordoned-off portion of the network. “Based on the alignment, small holes are made directly above the pipe. Measuring the gas that settles in the holes gives an indication of a leak,” says Asim. The reliability suffers, however, when the pipe’s diameter is not consistent across a length.
Another mechanism measures changes in pressure and sound caused by leaks. Sonar and magnetic equipment amplify this difference, just as the sounding rods or ‘mukdams’ of yesteryear did manually. These are largely ineffective, writes Nikhil, due to the high levels of background noise in the day, and the contrariwise lack of water flow in the night. Internationally, waterproof microphones are let into pipes and heard through using a speaker.
The Praja report found all water-related complaints took an average of 29 days to resolve (in 2020), as opposed to the prescribed 1-7 (depending on the type of complaint).
Where is the water lost?
Slums are often conveniently blamed for unauthorised water tapping. While more than 2.5 lakh metered connections are in slums (as of 2019), they receive only 45 lpcd – 90 litres less than the daily norm of 135 lpcd. Non-notified slums (that have come up after 2000) are denied even this, or in some cases, are given a common non-metered stand-post connection. The remainder is made up by neighbouring communities, tankers, or bottled water.
“The government is aware of illegal water tapping and tankers. But on humanitarian grounds, they are ignored,” says Subhajit Mukherjee.
But by Sitaram’s calculations, slums cause only 3-5% of Non-Revenue Water. The bigger share of the pie, he says, is routed informally to big companies, the hospitality industry, industrial estates, and building complexes. “It is organised crime, facilitated by the BMC,” alleges Sitaram.
And even when slums are the target consumers, they are most often not the ones doing the tapping. “That is done by a nexus of BMC officials, political party members, local goons and the police,” he explains. Desperation and scare tactics force slum residents to buy the water sold at over 100 times the official price.
Asim estimates the slum’s share is not more than 10% and is a higher contamination threat than volume loss.
Citizen complaints play a part here too, with 859 of them in 2020 reporting unauthorized tapping in water connections.
So what’s the fix for water leaks?
Much of the BMC’s current efforts to reduce leakage concentrates on replacing infrastructure. 78 kms of pipeline, 461 valve chambers and 13,700 service connections are set to be renewed in 2021-22. Four tunnels are under construction to improve the conveyance system, and many more are proposed. BMC’s budget estimates indicate a total cost of Rs 75,500 crore.
“The new pipes are long-lasting and have sensors to help with detecting leaks. They are not as deep, so they are quicker to lay and repair. Non-toxic chemicals will also be mixed in water, so the pipes don’t corrode. It’s a very futuristic plan,” says Subhajit. The work has picked up pace after the lockdown but is likely to go on for 3-4 years. Areas with pipes in poor condition and low water pressure are the priority.
Asim recommends a combination of good metering, accessible valves at ground level, flow and pressure sensors, and better construction standards followed by contractors for an effective reduction in leakage losses.
The BMC is concurrently developing new sources of water – the Gargai and Pinjal dams, for future demand, that will supply 1,305 MLD. Perhaps it is time to look within the city.
Corrigendum: This article has been updated to reflect the latest data.