Lessons from the Cholas - Part one

Published on by in Case Studies

Lessons from the Cholas - Part one

A return to the past could help Chennai’s water woes

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.

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.