Environment
Climate change is expected to intensify the potential for flooding and drought around Chennai, but remembering the Chola Kingdom offers solutions to the city’s water woes.
A man stops at Kilkattalai Lake on an afternoon in early September.

This is part one in a three-article series on how the Chola Kingdom can teach modern-day cities to outlast droughts and floods. Part two can be read here and part three here

Thirunavukkarasu Sonachalam stepped out of the passenger door of an SUV on a recent September morning and onto Chennai’s 200 Feet Radial Road, a highway that trudges through Kilkattalai Lake, cutting it into two unequal chunks. He wore glasses and a white, half-sleeve button-down under close-cropped gray hair as he walked around the front of the vehicle onto the bank of the lake’s bigger half, talking about how withered it was before Care Earth Trust, the nonprofit he works with as a hydrologist, restored it. 

To get to Kilkattalai Lake from the nonprofit’s offices near the airport, one must drive past a bunch of buildings on several roads that were all built and paved atop a giant marsh, which is to say one must drive through Chennai. Just before rolling to a stop on the side of the highway, we passed a wedding hall, an ad for smart TVs, an Indian Oil petrol bunk, and a dusty Maruti driving school. Many of the lots in between were thick with overgrown reeds and glazed with standing water, the marsh bubbling up in the absence of concrete or asphalt. 

“All this was built by forgetting the water bodies,” Thirunavukkarasu said. 

His task — and the task of Care Earth Trust — is to remember the water bodies and help water flow through the marshland as it did before being trampled by millions of people. Doing so would, in a sense, return the city to around 850-1280 CE, when the Chola Kingdom controlled what is now Chennai and much of South India by mastering control of their water supply. They lived during a time when — in some ways similar to now — rain often fell in sheets or not at all, and so they ramped up construction of water tanks (manmade lakes) and temples that were also used to store water. Tamil Nadu alone still has more than 41,000 tanks and nearly 2,400 such temples, according to a 2017 paper about the Chola’s adaptability to climate change published in The Anthropocene Review, and this plethora gave the Chola local access to water. This network also allowed overflow to run from one tank to the next, rather than simply flooding the surrounding area. Rediscovering how the Chola tied water flow to water storage could help Chennai deal with its standing water, near-constant drought, and seasonal flooding threat. 

Restoration and reengineering 

With the government’s blessing, Care Earth Trust targets individual lakes or tanks for restoration. They start by digging through British records that can date back to the late 1800s, comparing the lake’s past and current capacity, trying to figure out how much it’s shriveled in the last 140 years or so. At Kilkattalai, Care Earth Trust led an effort to rip out reedy water hyacinth that had colonised much of the surface, a sign that the lake was clotted with sewage on which the weed thrives. They then carved out silt from Kilkattalai’s bottom, deepening it, which allows it to hold more runoff from nearby bodies of water. The group can’t always reengineer the flow of water around a lake — a few buildings and other blockages have come up since the year 1200 — but they ask the government to clear what they can without displacing people who have had little choice but to make their home on the water’s edge. 


Construction near lakes and other water bodies continues despite efforts to restore them. 

Though the Chola’s tanks have eroded with time and disuse, evidence shows they have helped people survive climatic shocks hundreds of years after the kingdom faded. The catastrophic drought of 1878 killed around 1.5 million people across South India, but spared a surprising number who were surrounded by water tanks in what used to be the center of the Chola empire, according to the 2017 paper in The Anthropocene Review. 

“The Cholas were always doing planned development,” said Jothiganesh Shanmugasundaram, one of the paper’s co-authors. “That’s why we are able to see their vision even after 1000 years.” 

Jothiganesh said deepening lakes is only the start of reengineering a more natural relationship between cities and the water that flows through them, but he can see a future in which Chennai and others look to the past to begin freeing themselves from constant water crises.

“Reengineering might work,” he said. “I think it’s possible.” 

That said, it wouldn’t be easy.

How to fix Chennai’s water woes 

Chennai’s water problems are threefold. First, it’s in a near-perpetual state of drought because rainfall is becoming more erratic, people are sucking out its groundwater like the last droplets through a straw, and it’s covered in concrete that stops rain from seeping into the earth. Second, surface water stagnates in plots of land or along roads and essentially never evaporates. Then there are the city’s occasionally disastrous floods, caused in part because excess water can’t find its way into lakes, the ground, or out to sea. 

Beginning to fix these problems, according to Balaji Narasimhan, an engineer at the Indian Institute of Technology, Madras (IIT-M) who studies how people and climate change affect hydrology, will require a great many things. 

Lakes and tanks will need to be deepened to allow room for stormwater, and waste management will have to stop sewage from oozing to the bottom of water bodies, shrinking the capacity of lakes as it poisons them. 

The government will have to check pipes and other mechanisms through which water flows from one tank to another, making sure they’re wide enough and haven’t been destroyed by a bridge or a road. Drains in Chennai are often built to handle storms that occur every two-five years, which Balaji described as an international standard, and some of those might need to be replaced by more drains that can absorb hundred-year downpours. 

Chennai will also have to do something about its irrigation channels. Many of its tanks used to store water that flowed along these channels to nearby crops, but the farmland has since been replaced by buildings and roads, and the channels are now used as “drainage canals” that actually just release water into the middle of the city. That leads to another issue, which is that Chennai is flat. Much of the city’s drainage relies on gravity, which only goes so far if gravity has nowhere to pull the water. Pumps that are able to push the water out of the metropolis would be better, Balaji said. 

Checking unplanned construction 

Then there are Chennai’s roads, which grow some inches in height every year because the government repairs them by slathering new asphalt right over the old. Some roads gradually come to sit above their surroundings, meaning water runs off them and into buildings and homes.

“When you look at urban infrastructure, there is a lot of confusion,” Balaji said. 

Much of that confusion comes from unplanned construction that gives little thought to how buildings will affect the surrounding landscape. 


Kilkattalai Lake again looks like a lake after Care Earth Trust ripped out a field of water hyacinth that had taken over its surface. 

Driving to another lake Care Earth Trust has rehabilitated, Thirunavukkarasu passed an apartment building that backed up to the edge of a sizable pond, so close that residents could leap out their windows and into the water. The building, obviously built on top of marshland, was clearly stifling the pond’s ability to drain into the spongy ground nearby. The pond would also almost certainly become more polluted by the year just because of its new proximity to people. But there it was, an everyday reminder of the damage people are doing to the water bodies that could help sustain them. 

“At this level, it’s very difficult to reclaim [lakes], to go back to the original condition,” said Reshmi Devi, an expert on surface water hydrology at BMS College of Engineering in Bengaluru. “We are left with not many solutions.”

Still, Balaji pointed out that most lakes and tanks in Chennai are still connected to the canals and other water bodies around them, even if some of those connections are partially blocked. Revitalising a lake takes time, government approval, and a lot of manpower, but it still has a chance to make the surrounding area a little less susceptible to drought, flooding, and stagnant water. 

Cities can also think more about water when considering the construction still to come. Urbanisation is not about to stop, but it doesn’t have to be unplanned and swept with concrete.

High-rise buildings can house more people while using less ground, and the bases of those buildings can be made with material more permeable than concrete, according to Vinoth Kumar, an architect and urban planner at the Chennai Academy of Architecture and Design. 

Developers can also create small green spaces within cities. If apartment blocks devote half their land to open ground, that space can serve as a “buffer” that allows water to flow into the earth, according to Nagesh Kumar, a water resources and environmental engineering expert at the Indian Institute of Science (IISc) in Bengaluru. If developers allow much larger green space to flourish between cities and suburbs, that space can help slow urbanisation while filling up the groundwater table. 

Climate change is expected to intensify the potential for flooding and drought around Chennai, and every day more people arrive in search of work. The city — and others like it — can either grow in a way that allows water to ease the climate problems to come, as the Chola did, or it can let the whims of rainfall dictate just how long the city will remain livable. 

Colin Daileda is a freelance journalist in Bengaluru who has written about climate change for Thomson Reuters, and on other subjects for The Atlantic, Roads and Kingdoms, Mashable, and others. 

All photos by Colin Daileda.