Velachery lake encroached 75%, Retteri & Ambattur 40%; shrinking lakes add to Chennai’s flood, drought misery

CHENNAI: It once sprawled across nearly 221 acres, bailing out the neighbourhood by taking in floodwater during rains and recharging the groundwater table for summers. Now, a few decades later, the Velachery lake has shrunk to less than 53 acres – or less than 25 per cent of what it was – while the rest has been eaten away by encroachers. Little wonder, then, that Velachery is among the worst-hit areas in the city during every rain.

This is not an isolated case. Many other waterbodies around the city suburbs like Ambattur and Perungudi lakes and Rettai Eri have also lost a substantial portion of their spread to encroachment (see box) between 1972 and 2019, as established by a recent study titled 'Impact of Rapid Urbanisation and Encroachment on the Major Lakes of Chennai: A Spatial Analysis', conducted by a team of researchers from Presidency College and Nilakottai Government Arts College for Women.

Attributing the 2015 floods and 2019 water scarcity to the diminishing extent of wetlands, the report said that the amount of rainfall in 2015 was excessive but not unprecedented. The damage inflicted on the city was made worse by the destruction of species-rich wetlands and natural drainage systems, which used to shield people from the worst impacts of both droughts and floods, it said.

Citing the case of Velachery lake, the report said, “This extensive encroachment highlights the severe impact of urbanisation on Velachery lake, significantly diminishing its ecological and hydrological functions."

It added that continuous monitoring and proactive management were essential to preserve the ecological and hydrological functions of these lakes, thereby supporting the environmental health and resilience of the urban landscape.

The 'Living Planet Report 2024' released by the World Wide Fund a few days ago pointed out that rapid urban expansion resulted in an 85 per cent decline in Chennai’s wetland area. "As a result, vital services that these ecosystems provide – including retaining water, recharging groundwater and flood regulation – were radically diminished, leaving the people of Chennai vulnerable to both droughts and flooding made worse by climate change," the report said.

Apart from Velachery lake, the team analysed Ambattur lake, Korattur lake, Perungudi lake and Rettai Eri by comparing historical boundaries from 1972 with satellite images of 2019. In 1972, Ambattur lake covered an extensive area of 287.23 hectares. By 2019, this had markedly diminished to 173.10 hectares. Water coverage is recorded at 114.13 hectares, indicating that only 60.27 per cent of the lake's original area remains as waterbody, the study report said.

On the other hand, Korattur lake is the least affected of the five lakes that the researchers studied, with only 4.25 per cent of the land encroached upon. In 1972, Korattur lake had an area of 244.31 hectares. By 2019, this area had slightly decreased to 233.93 hectares, with the present water coverage being 10.38 hectares.

In 1972, Perungudi lake encompassed an area of 16.03 hectares. By 2019, this area had decreased to 11.93 hectares, with the present water coverage standing at 4.10 hectares. Similarly, Rettai Eri covered an area of 223.22 hectares in 1972, which has reduced to 136.15 hectares, with water coverage recorded at 87.07 hectares by 2019.

A few months ago, the southern bench of the National Green Tribunal (NGT) expressed shock over the issuance of a government order alienating Velachery lake land in favour of the Tamil Nadu Housing Board (TNHB). The government ordered the alienation of Velachery Eri for Velachery Sites and Service Scheme, South Madras Neighbourhood Scheme, Thiruvanmiyur Neighbourhood Scheme, Valluvar Nagar Neighbourhood Scheme and Navalpattu S and S Scheme, and NHS Scheme that were already utilised by the housing board.

Following this, state chief secretary N Muruganandam directed the water resources department to explore the possibilities of increasing the capacity of Velachery lake by 50 per cent of its present capacity.