The Great Stink that the 17.9 -kilometre long Mithi river leaves, at its mouth near Mahim, can make someone nauseous. The other three rivers that criss-cross Mumbai - the Dahisar river, Poisar River and Oshiwara-Walbhat river, all smaller than Mithi, are virtually non-existent or are just sewage drains.
The situation of Mumbai's rivers is akin to the 346-kilometre long Thames, that flows through the heart of London, which was declared ‘biologically dead’ by the Natural History Museum in 1957. Thames had turned into a dustbin of London as industrial waste, untreated sewage among everything got routed into the river.
Though Mumbai doesn’t have the great industrialisation that London had, the commercial capital of India has seen migrants move into the city in large numbers and settle besides these rivers to run small scale industries that discharge industrial waste and untreated sewage into these rivers making it almost biologically dead.
Stringent laws and a clean-up measure from London authorities saw Thames get back its life and turn into one of the cleanest rivers, but it took close to six decades of work. But the Brihanmumbai Municipal Corporation (BMC), one of the richest municipal corporations in the country, seems to have a river rejuvenation plan only on paper.
Besides Mithi, BMC has planned rejuvenation and beautification of the other three rivers - Dahisar River, Poisar River, Oshiwara-Walbhat river, and has plans of developing them into tourist places. Experts, however, question whether BMC’s plan is really one of river rejuvenation?
Himanshu Thakkar, environmental activist and water expert and coordinator of South Asia Network on Dams, Rivers and People (SANDRP)- an informal network of organizations and individuals working on issues related to the water sector - has said that neither the BMC nor the state government seem to be serious about river rejuvenation.
"They first need to clarify their ideas on river rejuvenation. Secondly, the rivers in Mumbai have been channelised by constructing concrete walls, and they have now become drainage channels. However, it cannot even function as a drainage channel, with sewer and garbage entering it. In the name of rejuvenation, the civic body has snapped all the connections of the rivers. There is no system to report the health of the rivers," Thakkar said.
According to Thakkar, it is not enough to have technology and investment as boasted by the Mumbai civic body to rejuvenate the rivers, but serious effort, accountability and transparency are required. "There need to be sewage treatment plants (STPs) in place with sufficient capacity. Again, the problem is that in India, the majority of the cities have STPs with sufficient capacity, but most of them are not functioning as required, or violate the effluent discharge norms. It is high time that the Mumbai civic body understands the right way to carry out the rejuvenation. Just commissioning and upgrading STPs won't help the project; they need to have a process to ensure these STPs are functioning as required. "Thakkar suggests the civic body should upload the statistics of the functioning of the STPs on its website daily along with the names those in charge.
Consequences of poor sewage management in the city and how it is affecting the water bodies
With the situation having turned alarming, the BMC has to hurry up. However, the civic body has estimated the upgradation of the six STPs will not be completed anytime before 2026 to 2027.
Meanwhile, effluent discharge and poor sewage management has an adverse impact on marine biodiversity and ecology. At places where dilution is not good, particularly in creeks like Malad and Thane, whatever biodiversity existed is all missing now. Discharge of raw and primary treated sewage is resulting in the growth of mangroves, which is a negative indicator in such places. Along with mangroves, there should also be an increase in the number of birds and fish, but this is not happening. Mangroves are growing because the nutrients of sewage are ideal for them. Sludge of sewage gives nutrients to the roots of mangroves.
For example, mangrove density in the Thane creek has increased accompanied by an increase in flamingos visiting the area. However, the rise in the number of flamingos is actually an indication that all is not well. There are bacteria and different types of insects present in the water which flamingos feed on them. Thane creek’s holding capacity has more sludge and silt and not enough water. Fishermen are not able to catch fish and crabs, unlike in the past.
Meanwhile, on the western coast, Versova and Malad creek are getting raw sewage. The sand on the beaches in this part of the city is black.
"The marine biodiversity is almost non-existent and only in the monsoon, you can see some kind of creatures. The pollution not only makes Mumbai’s beaches unsafe for swimming, but contaminates the seas enough to make it unfit for fishing as well," said a marine biologist from Central Marine Fisheries Research Institute (CMFRI).
Over 700 megalitres of untreated sewage discharged daily into four Mumbai rivers
According to a civil appeal petition filed by the BMC in the Supreme Court, a total of 747 megalitres (a single megalitre comprises 10 lakh litres) of untreated sewage is released into four rivers in Mumbai every day. Starting from the Mithi River, which receives the highest quantum of dry weather flow (DWF) at 285 ML per day, followed by the Poisar river (67 MLD), Dahisar river (56 MLD) and the Oshiwara - Walbut river (17 MLD).“After the completion of the ongoing river rejuvenation projects, a major chunk of DWF, around 426 MLD, will be diverted into the existing municipal sewer lines/STPs,” said P Velarasu, Additional Municipal Commissioner (Projects) of the BMC. The BMC does not seem to have a clear plan of action for the remaining 321 MLD of DWF, environmentalists have alleged.
"Experts, and even IIT Bombay's report suggests there should ideally be 30-35 STPs for Mumbai, either ward wise or according to the requirement of the rivers. We have even suggested small STPs near the four rivers. However BMC officials have not shown any interest in these suggestions," said D Stalin, green activist and Director of NGO Vanshakti.
A comprehensive report submitted by team River March (an NGO that has been campaigning for the rejuvenation of Mumbai’s four rivers) to the Municipal Commissioner in 2019 stated that discharge of raw sewage, animal waste and garbage are the main causes of pollution in three of the city’s rivers — Dahisar, Poisar and Oshiwara.
“Many slums discharge raw sewage into the river. We have recommended that sewage lines should be laid in slums to stop discharge of raw sewage. We are not saying or suggesting anything new. The Chitale commission talks about STP plants, restoration of rivers, none of which has been implemented since 2006. Diversion of sewage from natural water bodies is the primary way to restore them. Neither has BMC upgraded and commissioned STPs, nor have they managed to restore the river so far but have concretised them in turn. It seems BMC is just not interested in restoring these rivers," said Gopal Jhaveri, environmentalist and co-founder of River March.
"Unless we have proper functioning STPs, sewer lines in place and the civic body stops discharging waste water in creeks, river rejuvenation will never be a success and public money will keep going down the drain," said Stalin.
From rivers to sewers - journey of Mumbai's four rivers
Mithi: This river originates from the overflow of Vihar Lake (built by the British sometime around 1860 to supply drinking water to the then Bombay) inside the Sanjay Gandhi National Park (SGNP) and also receives overflow from Powai Lake. It flows for about 17.9 kms before meeting the Arabian Sea at Mahim Creek and has the largest catchment area of 7,265 hectares (ha). The upper stretch of 11.8 kms of the river falls under the jurisdiction of the BMC, whereas the remaining downstream portion of the river is under the administrative control of the Mumbai Metropolitan Region Development Authority (MMRDA).
Mithi River forms the boundary between Mumbai’s island city and its suburbs. Mithi's plight came to light after the July 26, 2005 deluge in Mumbai. A fact-finding committee set up by the state government to find out the reasons behind the deluge had also blamed encroachment on Mithi and suggested its restoration. Since then, BMC and MMRDA both spent a lot of money on projects related to Mithi.
Mithi was named the most polluted river in the state in 2018, with water quality parameters much above Central Pollution Control Board (CPCB) standards. Concrete embankments along the river – an idea criticised by environmentalists – have been built along the river’s lower reaches along Bandra-Kurla Complex (BKC) as well as near its headwaters at Vihar and Powai lakes.
Over the years, the water quality of Mithi has deteriorated with slums and industrial units, which have come up on its bank, discharging sewage and industrial waste directly into it. In 2019, the water in the river was found to have the presence of fecal coliform bacteria 15 times higher than the standard limit.
In November last year, the BMC cleared four proposals related to rejuvenation of Mithi river. The work includes laying of sewer lines along the river, managing flow of the river by widening, deepening, construction of reinforced cement concrete protection wall and service road.
The other three rivers
Oshiwara River: Also known as Walbhat River it starts from the Aarey Colony near SGNP, cuts through the Goregaon hills and after a journey of seven kilometres, finally empties into the Malad creek. Its total catchment area is 2,938 ha of which 53 percent is built-up with slums accounting for 23 percent share (data for 2005).
Dahisar River: Mumbai’s third river originates from Tulsi Lake inside the SGNP and flows across the northern suburbs and meets the sea at Manori Creek after travelling for 12 kms. Dahisar River’s total catchment area is 3,488 ha, of which 24 percent is built up (data for 2005).
Poisar (Poinsar) River: This too starts from SGNP and flows for about seven kms to end its journey at the Marve Creek. As of 2005, almost 53 percent of its catchment was already built-up. In the last 13 years since 2005, the built-up area in the catchments of these rivers must have gone up tremendously.
All these four rivers together form the natural stormwater drainage (SWD) system of Mumbai that carries excess rainwater (run off) from various areas of the city, emptying it all into the creeks and the Arabian Sea. This drainage network is crucial for Mumbai, as the city receives a heavy annual rainfall of over 2,400 mm within the four months of June, July, August and September. Also, large parts of Mumbai are barely above the sea level (some even below sea level), and are thus prone to regular flooding.
For Poisar, Dahisar and Oshiwara rivers, in all, about 17.5kms of fresh sewer lines, 16.5kms of stormwater drains, 16 drainage interceptors and 17 small capacity sewage treatment plants will be built over the next four years. According to BMC the locations the civic body is looking at for installation of STPs include Sukurwadi and Indira Nagar along the Dahisar river; Kranti Nagar, Gokul Nagar. Durga Nagar, Poisar Subway and Sanjay Nagar along the Poisar river; and near the Hindu cemetery in Aarey Colony, which is aimed at tackling a significant quantity of wastewater that is discharged from the dairy industry there.
The Mumbai civic body had received responses from ten bidders for this. The BMC has told the Supreme Court that the tendering process has been delayed due to the pandemic. Tenders that were invited in April and May 2020 are yet to be awarded for works on the three rivers
Additional Municipal Commissioner, (Projects), P Velrasu said, "Rejuvenation of rivers includes widening, improving the quality of water, curbing pollution of rivers, creating sewer networks, constructing desilting access roads, beautification of river banks and building Sewage Treatment Plants. The project involving the three rivers will cost about Rs 1,400 crore.
Tenders for the rejuvenation of the Dahisar, Poisar and Oshiwara-Walbhut rivers were invited last year. However, the BMC is yet to finalise the contractors for the project. “The process of appointing contractors for the rejuvenation project is in the last stage. We have already sent our reports on the project," said Laxmivenkatesh Kamlapurkar, Chief Engineer - Storm water drains (SWD) Department.
In the 2021-22 Budget, the civic body had announced its 'river rejuvenation project'. As part of the project, the process of river widening, curbing pollution and desilting works is to be carried out in a phased manner.
According to officials from the Storm Water Drain (SWD) department, the project will take about 36 months to complete once contractors are appointed.
“While for Dahisar and Walbhat rivers, three firms each have shown interest, for Poisar, four companies have expressed interest in executing the project. The process of finalizing contractors is going on,” said an official from the SWD department.
“After completion of rejuvenation, the firms will also be appointed for maintenance and operation for newly developed tourist places on the banks of these rivers,” the BMC official said.