As the first light of dawn paints the sky in hues of orange and gold, 17-year-old Ravi steps out of his home. The cool breeze brushes his face as he walks towards the expansive, 150-acre Sembakkam Lake for his morning bath. Millipedes and blanket worms scuttle across the road, their movements as steady as a train on its tracks. A flock of white pelicans glides across the sky as he nears the lake, where a few people fish in the serene waters. After his bath, Ravi returns home to prepare for college.

This was M Ravi’s experience as a young man in 1974 when Sembakkam Lake was still a thriving part of his community. Now 62, Ravi recalls those mornings with nostalgia. Today, the lake has shrunk to 104 acres, and a stagnant pool of black water remains. As Secretary of the Sri Sarvamangala Nagar Residents Association, Ravi has been at the forefront of efforts to restore Sembakkam Lake for the past 25 years.

In Part 1 of the series on pollution of water bodies, we examine Sembakkam Lake’s deterioration and the challenges residents and environmentalists face in their fight for its conservation.

The decline of Sembakkam Lake

As Ravi explains, agricultural land once surrounded Sembakkam Lake. Over time, much of this land was converted into residential plots. However, the government failed to provide essential infrastructure, such as an underground drainage system, to manage the growing urban sprawl. As a result, raw sewage from surrounding buildings has been flowing directly into the lake and nearby water bodies, worsening the environmental crisis. Decades later here we are trying to find the missing links in dire straits.

Read more: Saving the eri: How communities came together to restore Chennai’s lakes 

The water flow and natural connections

Sembakkam Lake was once part of a larger water network. Water from the Pachamalai Hills flowed into Chitlapakkam Lake, which in turn fed into Sembakkam Lake. Ravi recalls, “Pachamalai channel used to have hip-level water. To reach the Hasthinapuram bus stop, we would cross the 30-foot-wide Pachamalai channel in the 1970s.” Currently, the channel is almost unrecognisable, and the natural water connections have been severed due to rampant urbanisation.

The impact of urbanisation

Meanwhile, in a significant change, surplus water from nearby Selaiyur Lake is now flowing entirely into Sembakkam due to encroachments and altered natural pathways.

Darwin Annadurai, an environmental scientist at Eco Society India explains, “A portion of surplus water from Selaiyur Lake once flowed towards Chitlapakkam Thangal (Chitlapakkam Thangal is a separate water body, which was situated at a lower elevation from the lake). But now the Chitlapakkam Thangal and the channels connecting Selaiyur Lake to Thiruvanchery Lake and Rajakilpakkam Lake have disappeared because of encroachments and all the water flows towards Sembakkam.”

This disruption in natural water flow exacerbates the sewage issue. The inflow of untreated sewage from both residential and commercial buildings — into lakes like Chitlapakkam and Selaiyur— has made these water bodies a dumping ground for raw sewage.

To address this issue, Chitlapakkam residents have come up with a solution to divert the sewage water entering the lake.

Chitlapakkam’s 4Ds model

The 4D model of Chitlapakkam involves deflecting, draining, desilting and deepening. “All the inlets to the Chitlapakkam Lake have sewage gates from where the polluted water is deflected through the sewage interceptor drains and taken to sewage collection wells. From the collection wells, it is taken to a conventional Sewage Treatment Plant (STP) through pumping arrangements. During non-monsoon, sewage is not allowed into the Chitlapakkam Lake,” explains Dayanand Krishnan, a GIS expert and member of Chitlapakkam Rising. All this can be done within Rs 10 crore and can help in storing rainwater in the lakes and mitigating floods, he adds.

“As of now, we are diverting the sewage water from Chitlapakkam Lake to Sembakkam Lake. The collection well construction is close to completion and pumping arrangements have been made to pump the sewage from Chitlapakkam Lake into the STP. It should be operational in a few weeks,” says a WRD official.

As a result, Sembakkam Lake receives sewage water not only from Chitlapakkam Lake but also from Selaiyur Lake (which carries polluted water from Irumbuliyur Lake) and the buildings in Sembakkam. “This leads to flooding in Sembakkam and the surrounding areas during the monsoons,” says Ravi.

So, the two missing links in the entire system are Sembakkam to Nanmangalam (90% completed) and Nanmangalam to Keelkattalai. “We could prevent flooding once this work is over,” says the WRD official.

Read more: Lessons from the past must guide the restoration of Chennai’s lakes

Encroachments and government neglect

However, it is not just flooding and sewage. Over the years, both government and private entities have encroached upon the lake. “First came a Pillaiyar temple and then a political flag post, marking the first encroachments in Sembakkam Lake,” recalls Ravi.

Owing to the relentless efforts of Ravi and Sri Sarvamangala Nagar Residents Association, and the legal battles they took up, Sembakkam Lake still has 104 acres. Other lakes nearby have lost more than half of their catchment areas to encroachments.

Sembakkam Lake needs restoration, not lakefront development

Meanwhile, CMDA has allocated Rs 10 crore for the lakefront development of Sembakkam Lake. “We do not want any amphitheatres, parks or concrete pathways along the lake bunds. We want a clean lake in which rainwater can come naturally and flow to the next downstream lake without flooding the area,” says Ravi.

The WRD official says that the detailed project report (DPR) will also include sewage deflection and the setting up of peripheral drains along with the usual lakefront development works. The Chitlapakkam model does not hold good for Sembakkam Lake, as Chitlapakkam has point flooding and a much lesser catchment area. On the other hand, Sembakkam sees flash flooding and has a larger catchment area. “We will make slight modifications to the Chitlapakkam model to address this,” adds the WRD official.

Many issues get entangled in jurisdictional conflicts between different government departments, and Sembakkam Lake restoration is no exception. The WRD along with Tambaram and Pallavaram Municipal Corporations need to take proactive measures to stop the sewage inflow in the lake.

As I spoke with Ravi, I realised that the vibrant lake ecosystem he once knew may never be experienced by my generation. The question remains: What will be left of this lake if we don’t act now?

Also Read:

• Saving lakes in Chennai: Why maps and physical markers are critical
• Why Bengaluru must preserve and restore its lakes