Saul Kere, a lake off Sarjapur Road, was once a thriving habitat for birds. “When I started birding regularly in  2019, I had observed nearly 180 species of birds here,” Bijoy Venugopal, a birder and environmentalist, recalls. “Even during our latest bird walk on December 7th, we recorded 67 species of birds, more than what you would see at some bird sanctuaries.” However, the number of birds has declined, mainly due to effluent inflow.

E-bird, a public data forum, has a record of 213 bird species in Saul Kere. That is the richness of the biodiversity of the Saul Kere (variably denoted as Sowl Kere or Soul Kere). Unchecked urbanisation polluting Bengaluru’s lakes is, unfortunately, a long-familiar story. Saul Kere’s story is not too different either. Despite being one of the few remaining natural wetlands in the city, the lake is slowly being transformed into a construction site, choked with sewage and surrounded by encroachments and unplanned infrastructure work.

A haven for migratory birds

Saul Kere’s ecological uniqueness lies in its varied depths — a mosaic of shallow and deep zones that supports diverse flora and fauna. This natural wetland structure makes it a thriving ecosystem for resident and migratory birds. Pelicans, painted storks, herons, and cormorants have long nested and foraged here.

Even after a major fish kill last year due to sewage contamination, pelicans returned, a stark reminder of both the lake’s resilience and the dwindling alternatives for birdlife in Bengaluru. “They came back because there’s nowhere else left for them,” says a local volunteer from the Saul Kere Mitra group. 

Bijoy has also observed fish kills over the past few years. “There has been a lot more eutrophication, due to sewage inflow,” he alleges. “So, the quality of the habitat for biodiversity has deteriorated significantly in the last four or five years. And as a result, we’re seeing fewer birds than we used to see earlier.”

Read more: Saving Bengaluru’s lakes: Why BBMP should institutionalise community participation

Sewage flow into the lake

Based on his observations, Bijoy explains that during heavy rains, effluent from sewage channels often mixes with stormwater from the drains, leading to contamination. But Rashmi Hari, a member of a citizen volunteer group, Mahadevpura Parisara Samrakshane Mattu Abhivrudhi Samiti (MAPSAS), says that the sewage channel is directly connected to the stormwater drain at the south-east entrance.

According to citizen groups working on the lake, Bangalore Water Supply and Sewerage Board (BWSSB) began underground drainage (UGD) pipeline work in June 2023 along the northern buffer zone of Saul Kere, laying 300mm and 800mm diameter pipelines. The sewage pipelines that were put up in the past four to five years, especially during the COVID-19 pandemic, are directed to this lake. “The eateries surrounding the lake are also sending the sewage to the stormwater drain,” Rashmi adds.

Meanwhile, a Biome Environmental Trust report lists how the inlet canals allow a mix of sewage and stormwater.

A diversion channel is meant to redirect polluted water away from the lake to protect its quality. However, a sewage channel runs close to the bunds, and during rain it overflows into the lake. Rashmi observed that in the last rains, sewage overflowed onto the bund, making it impossible for people to walk there.

Bijoy agrees. “Regular maintenance of the primary stormwater drain (raja kaluve) could reduce the pressure on the lake, but the BWSSB authorities work half-heartedly, only when there is pressure from the public,” he says. Residents report that bunds have been cut for excavation, fences have collapsed, and construction has encroached on the lake’s buffer zone — violating National Green Tribunal rules that ban such activity within 75 metres of a lake, as well as the Karnataka Tank Conservation and Development Authority Act, which prohibits construction within 30 metres.

Read more: Lake Health Index reveals pollution concerns in Bengaluru’s water bodies

Proposal for a sewage treatment plant

According to a Bangalore Mirror report, the BWSSB has proposed the construction of an industrial-scale STP at a capacity of 28 MLD in Saul Kere. The project has since expanded to a ~40 MLD capacity STP, MAPSAS noted.

The lake has two micro STPs with a combined treatment capacity of 1 million litres per day (MLD) of sewage. In a letter to the Karnataka Tank Conservation and Development Authority (KTCDA), MAPSAS raised concerns about the construction of an STP within the lake’s buffer zone. The letter notes that the lake, with a water spread of 196,980 sq.m, requires only 1.8 MLD of water to offset its trans-evaporation loss. Moreover, the proposed ~40 MLD capacity STP, intended to serve upstream lakes, is classified as an Urban Public Civic Amenity. Such amenities, MAPSAS argues, should be developed outside the buffer zone on government land designated for that purpose

 The sewage inflow is 40 MLD according to a report by The Hindu. While 1 MLD of treated water is let into the lake, the rest flows to the Bellandur Lake. An STP is required to treat water which is diverted to other lakes. “But just not inside the lake boundary or in the buffer zone,” Rashmi says.

“No public consultation was carried out, and BWSSB is very opaque in making such decisions,” adds Bijoy. 

 A BWSSB Projects Division official confirmed that the proposal was still pending at the government level. The official added that sewage entry to water bodies in the surrounding areas would be resolved permanently once the STP is constructed.

The project continues without any legal permits or land clearance. The works also seem to ignore environmental and planning permissions, despite the works being carried out in an ecologically sensitive zone.

STP is needed, but not inside the lake

“While many STPs are positioned adjacent to or in the lakes, there hasn’t been any significant improvement in the water quality,” says Raghavendra B Pachhapur, a birder with a passion for lake conservation. He adds that STPs are mandated to achieve Class D water quality, suitable for fisheries and wildlife. However, an ActionAid report reveals that most lakes remain at Class E, fit only for industry and irrigation. Not only are STPs failing their purpose, but building them within lake boundaries also threatens biodiversity.

Meanwhile, BWSSB maintains that the proposed STP is essential to stop sewage from entering nearby lakes — yet activists argue this justification cannot override legal safeguards for wetlands or replace sustainable alternatives.

Environmentalists and local groups, including MAPSAS (which manages Saul Kere and two other lakes in the area), have long advocated for decentralised STPs and source treatment systems as more viable options.

Read more: Why all Bengaluru lakes need a biodiversity survey: Lessons from Dorekere

Residents request the development to be carried outside the buffer zone

“There is land available outside the buffer zone,” residents insist, “but the authorities find it easier to build inside the lake precincts.” There are also unconfirmed reports that the BWSSB may shift the proposed large-capacity STP to Belagere, though no official communication has followed.

“When a space meant for biodiversity is taken up by bricks and mortar, the birds have nowhere to go. The noise generated from the STPs’ operations will disturb the birds and the ecosystem at the lake,” Rashmi says. “We just pray that they move the STP outside Saul Kere,” adds Shalini, another MAPSAS member.

Unless the sewage inflow is stopped, encroachments removed, and all illegal works halted, Saul Kere may soon lose its wetland character altogether. What was once a sanctuary for birds and biodiversity could become yet another example of how Bengaluru’s lakes are being engineered to death.

“Birds are resilient, and they will find their habitat. But that doesn’t mean that we should step back and be negligent,” Bijoy says.

Also read:

• Encroachment and drainage woes: Lessons to prevent flooding in Porur Lake
• Tale of neglect: Unchecked urban growth turns Mullur Lake into a sewage dump