Powai SOS: Call from a dying lake seeing a deluge of sewage water and covered in hyacinth

A further walk along the lake exposes colonies of hyacinths, so dense that it camouflages with the grass sprouting on the ground that surrounds it.

In March this year, Powai Lake’s deteriorating condition came to fore as the entire waterline of the lake was laden with dense vegetation including hyacinths.

While local residents alleged this was the worst case of vegetative invasion they had observed in the water body over the last few decades, it set off alarm bells over the water body’s depleting health across the city.

But there’s more to the lake than meets the eye.

A report commissioned by the Brihanmumbai Municipal Corporation (BMC) has found that over 18 million litres of sewage water is discharged into the Powai lake every day. This, for perspective, is equivalent to the total amount of potable water which Tulsi lake supplies to Mumbai city daily.

Sprawled over 210 hectares in the eastern suburbs, the lake is not only thronged by locals and tourists but also serves as abode to Indian marsh crocodiles, a species protected under Schedule I of Wildlife Protection Act, 1972.

It is located in the southeast of Vihar lake, with the surplus from its catchment area overflowing and channeling to the Mithi river through natural estuaries.

Jolted to action by public outcry, the BMC, this year, rolled out a Rs 108 crore plan to revive the lake.

Last month, the National Green Tribunal (NGT) also served notices to BMC, Maharashtra Pollution Control Board (MPCB), Maharashtra State Wetland Authority (MSWA) and the state government, directing them to submit a response by September detailing remedial measures and causes for neglect of the water body. A joint committee has also been constituted to submit a report outlining revival plans.

However, this is not the administration’s first attempt at restoration.

A rocky history

The youngest of the city’s three lakes, Powai lake has always been fraught with difficulties.

Over 130 years on, Powai’s waters continue to remain non-potable with the civic body now deploying it for industrial purposes (Express/Sankhadeep Banerjee)

It was in 1889, over concerns of an anticipated drought, that the erstwhile Bombay Municipal Corporation had sanctioned the construction of Powai lake. Planned to augment Mumbai’s water supply, Powai was artificially created as an auxiliary to Vihar lake, which albeit planned in 1860, was failing to meet the city’s water demands.

The lake was created at the site of erstwhile Kopri village, under the Powai estate, which was home to 23 huts at the time. The establishment of the project left the residents of Kopri displaced, with the lake constructed within a period of one year by 1890.

However, within five months, the corporation stopped drawing water from the lake amid several reports pointing to high pollution levels in the lake.

For many, Powai Lake’s ill fated abandon was a symptom of the larger lack of planning of water schemes in erstwhile Bombay.

Dr. Madhu Kelkar, who has extensively worked on the history of the water management system in colonial Bombay, said that the Powai lake was sanctioned in 1889 as a knee-jerk reaction to concerns over a water famine.

“Contrary to popular belief, the Powai lake scheme was completed by 1890 and it is very surprising that the project was completed within one year. Even though the lake is in a low lying area, the civic engineers had approved the location in its survey.

So, even though over Rs. 6 lakh had been spent for the scheme, water from the lake was drawn for only five months after which the idea was ditched. Two years later by 1892, the lake was completely abandoned,” said Kelkar.

The revival plans

As suburbs expanded and Powai grew, several plans were conceived to revive the lake.

In 1918, Kelkar says, the Bombay government had planned three schemes which included Aarey, Powai and Kanheri to cater to the suburbs’ rising water demand.

“Even though Aarey and Kanheri schemes were abandoned, a plan to revive Powai was finalised. This was also owing to growing anger amongst the suburban population, who despite having two lakes — Vihar and Tulsi — were facing water crisis,” she said.

According to records from the Maharashtra State Gazetteers, nearly Rs 5 lakh was spent yet again in 1919 in what was deemed ‘a vain attempt to restore the supply at least for the use of the suburbs’.

“However, once again, the scheme revival was abandoned after the Bombay Development Department (BDD) was created in 1920. While the BDD considered the scheme, it was abandoned as it was assumed that the Salsette island at some time in the near future would become part of Bombay municipal limits. Hence, it decided to depend on extended Tansa lake to fulfil the island’s needs.”

“After BDD was disbanded, the plan to revive Powai lake for water supply in the suburbs was once again planned in the 1930s but this time too, it yielded no positive results,” Kelkar added.

In the midst of its abandonment, the Powai lake was briefly given to a syndicate manufacturing Agave fibre in 1892 while in 1945, municipal records show that the lake was given to a trust for an annual rent of Rs 800 to draw water for a ten-year period.

Kelkar maintained, “However, we do not know whether the trust actually used the water from the lake.”

Over 130 years on, Powai’s waters continue to remain non-potable with the civic body now deploying it for industrial purposes.

Pollution woes and its sources

Despite being historically infamous for its murky, polluted waters, Powai Lake has always boasted of a rich and thriving ecosystem.

In a city gasping for space, the lake serves as a massive open landscape, surrounded by green hills. B N Kumar, director of the environment watchdog group, NatConnect Foundation, recalls that until at least 1979, the lake was thronged by mango orchards, making it a popular picnic spot for many, but with the spurt of residential clusters around the lake in the 1980s and the uncontrolled growth that followed, came the enormous burden on the lake. It was during this period that the IIT Bombay’s 1980 batch launched a ‘revitalization’ plan for the lake using sustainable techniques.

In 1995, the Powai lake was also selected as one of the ten lakes earmarked for improvements under the MOEEF’s National Lake Conservation Plan (NLCP).

In fact, in 2002, the NLCP released a fund of Rs. 6.62 crore for a restoration programme which was carried out by the BMC. Records show that the entire project was executed by March 2005.

However, despite the improvement projects, resident say that they first started noticing colonies of hyacinth thriving across the lake, over two decades ago.

“I have been coming to Powai lake for nearly 12 years. Earlier, the lake would host such rich biodiversity and I would spot diverse birds ranging from Grey herons, purple herons, spot billed ducks during my morning walks. But now, the migratory birds have all but stopped as the water has become so polluted. After rampant construction, I also noticed that hyacinths started growing on the water,” said Anamika Sharma, a Powai resident who grew up in the area.

In 2016 too, the BMC unveiled plans for revival of the lake through short-term and long-term measures like desilting which was slated to complete in 2019, but the lake health continued to deteriorate.

Pointing to ‘accelerated growth of residential, commercial and industrial areas around the lake’, the Urban Wetland/Water Bodies Management Guidelines, 2021 outlined by the National Mission for Clean Ganga and the School of Planning and Architecture in Delhi states that nearly 40 percent of the Powai lake has vanished.

Today, the lake is flanked by the busy JVLR road to its south, IIT Bombay campus to its north, commercial establishments like hotels, slum pockets as well as the residential complexes.

According to Abhijit Bangar, Additional Municipal Commissioner (Projects), nearly 18 MLD of sewage water is discharged into the lake from as many as 18 outfalls surrounding the lake. “Most of these outfalls are situated along the southern end of the lake. Some wastewater also discharges into the lake from unauthorised bastis,” said Bangar.

The 18 outfalls were identified in a report submitted by an external consultant, Tandon Urban Solutions Pvt Ltd., who was appointed by the BMC in 2023 at a cost of Rs 67 lakh to prepare the detailed project report for improving the water quality.

The report was commissioned after the NGT in 2022 had called for the constitution of an eight-member committee to draft a pollution remedial action plan for the lake.

Speaking to The Indian Express, an official from BMC explained, “There are nearly 18 storm water drains and culverts discharging into the lake. While these drains are meant for rain water, the rampant construction and illegal slums around the area has meant that a lot of waste water is also deposited into the lake through the drains.”

The report findings, accessed by The Indian Express, show that the worst quality of sewage water has been observed at the Peru Baug outfall wherein the BOD levels — which indicates the concentration of oxygen required for survival of aquatic life — were recorded at a whopping 72 mg/L for three days.

This is significantly higher than the accepted standards of less than 10 mg/L, which is the prescribed standard for the treated effluents permitted to dispose into the sea.

Overall, the BOD levels across the 18 outfalls ranged between 28 mg/L and 72 mg/L.

Many experts, including BMC officials, concur that significant discharge of waste water is one of the major contributing factors for the proliferation of vegetation like hyacinths.

What makes hyacinths dangerous is that it prevents sunlight from penetrating through the water, affecting the aquatic life and water quality.
Dr Rakesh Kumar, president for the Society of Indoor Environment (SIE), said that aquatic life is impacted owing to several factors ranging from heavy discharge of silt during rains as well as vegetation growth.

“When there is a lot of weed, algae, hyacinth, sunlight is prevented from seeping into the water, affecting the movement of water. Contrary to popular belief that lake water is still, churn of water is extremely important. When the sunlight penetrates naturally, the water column mixes on its own. But when the light seepage stops due to vegetation on the surface, the water becomes stagnant and makes it unhealthy,” added Kumar.

It was, therefore, in March, when the entire Powai lake was covered in a blanket of vegetation, that a group of 25 – 20 locals banded together to form the “Save Powai Lake and Environment group”.

“This was perhaps the first time that we had seen the entire Powai lake covered in hyacinth. For the past 24 years, I have seen so many citizen movements and so much money squandered into the lake and nothing has come out of it. Powai Lake is a part of us, so when we saw its condition our ALM decided to raise the issue,” said Pamela Cheema, a member of the Save Powai Lake and Environment group.

As visuals of the thick hyacinth growth took the social media by storm and the group amped up pressure over the lake’s deteriorating state, senior civic officials as well as politicians made a beeline to the site to assure of remedial measures. In May, the BMC fast tracked its plans for the improvement of lake water quality, with the objective of treatment of sewage at its core.

How does BMC plan to clean the lake

Having identified the total quantum of 18 MLD sewage water and its sources through its commissioned study, the BMC has charted an ambitious plan that seeks to intercept the divert and treat the large volumes of waste water discharging into the water body.

Valued at a combined cost of Rs 108.25 crore, the civic body floated two tenders in April, this year to detect, curb and divert sewage and sludge from flowing into a lake through a network of new sewer lines and a sewage treatment plant.

The first proposal — which is set to cost Rs. 39.37 crore — seeks to establish a 3056 metres-long (3.56 km) sewer line as well as 13 interceptors across the lake’s 18 outfalls, to ultimately divert the ingress to treatment plants.

According to the master plan, the longest network of 1.9 km will be established to control 8 MLD of sewage flowing in from nearly 14 outfalls, which will be diverted to the new STP proposed in Powai.

Apart from this, the proposal also seeks to intercept 8 MLD water flowing in from three outfalls near the IIT Bombay main gate, which will be diverted through the existing sewer line along the JVLR route and a new 942 meter-long network using gravity system.

Flowing into the lake from the Peru baug area, the remaining 2 MLD of the 18 MLD wastewater will be controlled and diverted to the Peru Baug pumping station through a 205 meter-long sewer line, which is slated to be built using the open cut method.

Through the Peru Baug station, the wastewater will be routed to the existing 9 MLD treatment plant at Mithi River.

Pegged at the cost of Rs. 68.88 crore, meanwhile, the second proposal seeks to establish an 8 MLD sewage treatment plant in Powai.

This new sewage treatment plant is proposed to come up in place of an abandoned sewage pumping station, which currently stands For this project — which entails demolition of the existing structures, construction as well as operation and maintenance for a period of six years — the BMC is eyeing to rope in a second contractor with expertise in the domain.

“Collectively, the two projects will intercept 18 MLD sewage water and then divert it for treatment. While the contract on the first proposal which seeks to lay over a 3km sewer line was awarded in June, we are currently in the process of evaluating the bids for the construction of the new STP in Powai. The process is likely to be completed over the next one month, following which work on the second project will also commence,” a senior BMC official told Express.

The plans — of laying sewer lines, interceptors as well as constructing a new STP — are projected to be completed over the course of the next two years.

In the meantime, officials maintain while the proposals will take off soon, that it continually cleans out the lake by removing the floating vegetation through machines ranging from poclains, harvester machines and dumpers.

However, when The Indian Express visited the Powai lake, earlier in August, the machines were amiss from action with all vegetation growth pushed to the fringes of the lake.

Amid filth and solid waste strewn along the periphery of the lake, a thick blanket of hyacinth covered the south eastern edges of the lake.

“Every day through our balcony, I see the hyacinth vegetation float from one part of the lake to the other. While the BMC claims that the lake has been cleared of vegetation, the fact is that the hyacinth has just been pushed to the edges because of the monsoon winds. The vegetation is so thick that it appears like an extension of the land, giving the illusion of the lake being cleared,” said Milan Bhat, a Powai resident.

While locals have welcomed the civic body’s plans, they have called for the immediate implementation of the project.

“So many projects have been announced in the past and yet, nothing took off the ground. This time, there is a hope as there seems to be some semblance with time bound plans. Having already lost so many decades, it is essential that the civic body implements the project at the earliest and improve the water quality,” added B N Kumar, who is director of the environment watchdog group, NatConnect Foundation.

He added that the civic body should also carry out desilting of the lakes, which are long impending, to improve carrying capacity while the muck can also be used as a manure.

Meanwhile, experts such as Dr. Rakesh Kumar said that what the lake demands is comprehensive conservation effort. “When we speak about Powai lake, it is not just about the sewage but about controlling pollution on other fronts like littering by tourists, improving overall water quality.”

Dr. Rakesh Kumar added, “While cleaning of hyacinths is important, that’s not enough. These hyacinths are fed by the nutrients in the sediments. Thus, we need a plan to target the sediments as well as address the high nitrogen and phosphorus levels in the lake.”