Chennai

The vanishing waterbodies of Chennai

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The area of the waterbodies in Chennai city and its suburbs has shrunk from nearly 12.6 sq. km. in 1893 to about 3.2 sq. km. in 2017, mainly due to urbanisation, a recent study has revealed

Names of places in Chennai are more than just geographical markers. They bring out what Chennai was not too long ago. Lake Area, Tank Bund Road and Eri Scheme are a few pointers that tell us how bountiful the city was in water resources.

Even as recently as in the 1950s, you could drive down Mount Road from Saidapet to Teynampet through what became CIT Nagar, bank left near where Gemini Flyover stands now, hop on to Tank Bund Road and continue motoring along, never too far away from water.

Cut to 2018: Chennai is all built-up and the names of places are just fluid reminders of the past.

It’s almost summer and the anxiety of Chennaiites is mounting. Despite official assurances, they are worried about how the supply of water will pan out. Today, motoring across roads means conducting tricky negotiations with water tankers that dominate not just our streets but other types of water supply too.

As the global community commemorated World Water Day recently as a reminder to use nature to overcome challenges and discussed the approaching ‘Day Zero’ in Cape Town, which is caught in the throes of a severe drought, Chennaiites recognise that their city is also part of the rather dismal scene. Rapid and unplanned urbanisation has systematically destroyed waterbodies, which act as sponges and help mitigate floods.

If the process is left unchecked, Chennai could soon be heading towards an ecological disaster.

Studying depletion

A study by the Department of Geology, Anna University, based on a city map of 1893, has revealed that there were nearly 60 large waterbodies in the core of then Madras. The study traced the shrinking and vanished waterbodies through a series of city maps.

In 2017, the number of waterbodies, both large and small, came down to 28.

 

Source: Department of Geology, Anna University

The historical map was sourced from the city maps prepared by the Edinburgh Geographical Institute in 1893. The rest of the maps were sourced through land satellite images, according to the team from Anna University.

“We found that the area of the waterbodies had shrunk rapidly after 1960 and there were drastic changes in the number of lakes or ponds in the core part of the city with every passing decade,” said Samurembi Chanu, a research scholar who was part of the team. The study covered the areas between Kodungaiyur, Tondiarpet and Guindy that formed the core parts of then Madras.

L. Elango, a member of the faculty at Department of Geology, Anna University, and vice-president of the International Association of Hydrogeologists (Indian chapter), said the area of the waterbodies in the city and suburbs had shrunk from nearly 12.6 sq. km in 1893 to about 3.2 sq. km in 2017, mainly due to urbanisation.

“The 1893 map indicates the presence of a crescent-shaped waterbody from the present CIT Nagar, Teynampet, Gemini flyover to Nungambakkam along the then Mount Road. The waterbodies, namely Mylapur tank and Nungambakkam tank, covered a distance of nearly 7 km,” he said.

The study aimed at checking the implications of urbanisation and climate change over ground and surface water resources and how the shrinking of open spaces had reduced groundwater recharge.

“Vysarpadi Lake, Perambur tank, Medavakkam tank and Spurtank were some of the large waterbodies that were replaced by buildings after the 1950s. While Nandanam was along the lake bund, the present CIT Colony was a waterbody during the 1950s. Kilpauk too had big waterbodies. Many small waterbodies in north Chennai near Tondiarpet have been wiped off city maps due to encroachment and urbanisation, particularly from the 1970s. There were a few ponds near Ice House too. The Madras Zoo that was located behind Ripon building and was later shifted to Vandalur in 1980s had a huge waterbody inside,” said Mr. Elango.

Impact on groundwater

The study estimated the depleting volume of water harvested and the loss of groundwater recharge as more waterbodies vanished over the decades. “We estimated that if the average depth of lakes and ponds was 2 metres and filled twice during a year, the volume of surface water stored has dipped from 1,335 million cubic feet (mcft) in 1893 to 339 mcft in 2017, going by the shrinking water spread area,” he said.

The vanished waterbodies and open spaces also mean a drastic drop in groundwater recharge potential, according to the study.

The rapid loss of natural resources has induced local flooding and increased saltwater intrusion in the coastal belt, noted water experts. They recalled a research project of IIT-Madras that estimated the existence of 650 waterbodies in the Chennai region till the late 1970s.

Every episode of local flooding in the city can be traced to a vanished waterbody in the neighbourhood M. Karmegam Former director, Centre for Water Resources, Anna University

S.P. Chairman, retired engineer, Water Resources Department, said some of the railway stations, including in Kodambakkam and Nungambakkam, were developed over lakes. A sizeable chunk of Chennai Central railway station was built above the Buckingham canal. Several ponds in Kolathur have yielded to infrastructure development.

“Until the 1960s, there was a big lake in Perambur on the site now developed as a park beneath the flyover. Low-level areas face inundation as lakes have been destroyed. The industrial estates in Guindy and Ambattur were also water bodies,” he said.

Man-made flooding

The Chennai floods of 2015 were a clear indicator of mismanagement of lakes and negligence in protecting linking channels. M. Karmegam, former director, Centre for Water Resources, Anna University, recalled that there was a chain of 16 tanks in Vyasarpadi, among which was the one in Kodungaiyur. After 1950, many have been turned into settlements, including in Ayapakkam and Koladi. The Public Works Department used to maintain tank memoirs with hydraulic details of tanks during the British period. Every episode of local flooding in the city can be traced to a vanished waterbody in the neighbourhood, he added.

Waterbodies have a role in temperature regulation, prevention of water-borne diseases and groundwater stabilisation Arun Krishnamurthi Environmentalist Foundation of India

Environmental activists noted that the trend was not new to the suburbs either. Arun Krishnamurthy, Founder of Environmentalist Foundation of India (EFI), noted that small ponds were easy prey as there weren't any proper revenue records. Ponds have been closed to build overhead tanks in Tiruvottiyur, Palavakkam and Thoraipakkam.

“There are different versions of documentation on waterbodies which were denotified during changes in land-use pattern. Every waterbody has a role in temperature regulation, prevention of water-borne diseases and groundwater stabilisation,” he said.

Coping with the loss

EFI is now involved in rejuvenating smaller ponds to sustain the ecological balance in areas such as Madhavaram, Gerugambakkam, Sholinganallur and Mudichur. With intense rainfall in short spells predicted to increase and bring more rainwater runoff in the city, experts call for a restoration of shrinking waterbodies and monitoring of rainwater harvesting on a large scale.

The study recommends demarcation of groundwater protection zones, construction of check dams across waterways and additional subsurface storage tanks to cope with the loss of natural resources over the past century and adapt to climate change.

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Printable version | Dec 9, 2019 5:42:57 PM | https://www.thehindu.com/news/cities/chennai/the-vanishing-waterbodies-of-chennai/article23404437.ece

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