The Eris System
The people of Chennai don’t have to look far for inspiration on how to work with nature to finesse water cycles. Starting at least 2,000 years ago, ancient Tamil people ensured that they had water year-round by building a series of connected ponds on a slope from the Eastern Ghats (“mountains” in Hindi) east to the Bay of Bengal. These eris, the Tamil word for tanks, are open on the higher side to catch water flowing downhill, while the lower side is closed with an earthen wall called a bund. An overflow divet in the top of the bund gives excess water a path to continue on to the next eri downhill. “System eris” were built off of rivers and creeks to capture their peak flows, while “non-system eris” were dug in areas without natural waterways to capture rainfall in a series of connected depressions. Eris were described in early Tamil literature and temple engravings, says Krishnakumar TK, an amateur historian and local travel writer who works in information technology and goes by the name KK.
The eris system is the opposite of modern development’s tendency to move water off the land as fast as possible. The early Tamils understood that, by slowing water’s flow, the eris reduced flood peaks and prevented soil erosion. They gave water time to seep underground, filtering it and keeping the water table within reach of wells. The eris also served as visual indicators of water availability because they were connected to the water table, says Vencatesan. Seeing the water level in a pond signaled to farmers when to sow their crops. Cultural rituals dictated system maintenance and water sharing. Tanks were also part of every temple complex, bringing water into the heart of religion and culture.
And because many eris were connected to creeks, rivers, coastal wetlands and freshwater marshes, they provided natural waterways their due along the way. Even eris not directly connected to rivers helped to feed the local hydrology because underground aquifers are extensive, so water absorbed in one place could feed a river some distance away. The words “lake,” “tank,” and “water body” are interchangeable here because, after so many generations, no one remembers whether a particular water body is natural or human-made.
British engineers in the 19th century were amazed by the scale of the eris system—reportedly more than 53,000 bodies of water across southern India—and the deep knowledge of topography and hydrology required to build it. Alas, British respect had limits. Their centralized management supplanted the traditional system by which villages managed their local eris themselves, removing accumulated silt each year and using it to fertilize fields. The British neglected this maintenance and the eris fell into disrepair, making it easier to justify filling them in and building on top of them—a pattern that continued after independence.
As they built roads, the British obliterated the flow pathways that had linked water bodies, says KK, giving the rainwater nowhere to go. “They did not understand our system,” he says. Today, many famous city landmarks and neighborhoods—Loyola College, Central Chennai Rail Station, T. Nagar, Nungambakken—sit atop former tanks and lakes, says KK. Street names such as Spur Tank Road and Lake View Road commemorate ghost water bodies that once sustained and protected their neighborhoods. Fewer than one-third of the 650 water bodies that KK has documented in and around Chennai remain. The surface area of water decreased from 13 square kilometers (5 square miles) in 1893 to less than 3 kilometers (1.1 square miles) today, so in heavy rains, water floods into city streets, homes, and businesses.
Ironically, given KK’s passion for finding and documenting historic water bodies, the IT company he works for is in a special economic zone built atop Pallikaranai Marsh and the neighboring Perumbakkam wetland. He chuckles ruefully, showing me the area on a map. “We used to have hundreds of thousands of migratory birds visiting this marshland some 20 years ago. I have seen [it] getting destroyed in front of my eyes.” With just 10 percent of the marsh area remaining, “Even I can’t [see] the water from my workstation, and I’m on the fourth floor.” But as the title of Krupa Ge’s book invokes, Rivers Remember. This area hasn’t forgotten it is a marsh. During the 2015 monsoon, it flooded to the second floor.
Wetlands = wastelands
Another British legacy that facilitated the destruction of wetlands was their official designation as wastelands. To Jayshree Vencatesan, the notion of wetlands as wastelands is anathema. “I grew up in the hinterlands, where this notion of waste doesn’t exist,” she says. “To us, nothing is a waste.” That attitude was once widely shared across southern India. Many areas the British saw as “waste” were shared-use commons, called poromboke in Tamil and dating back to medieval times. The ethic surrounding the use of the commons is even older, says Vencatesan, rooted in Tamil scriptures, which described the resources that wetlands provide—fish, seasonal agriculture, fodder for animals, medicinal plants—as well as the requirement to protect them, including penalties for those who didn’t. People understood and accepted that wetlands and other ecosystems were multifunctional habitats, supporting not just humans but other organisms as well. As a common property resource, water was subject to rules regarding how it was allowed to overflow from one water body or wetland to another. “This is essentially upstream-downstream equity, you know?” she says.
As she learned more about wetlands throughout her career, in part by working with Indigenous people who continue to live close to the land and water, Vencatesan internalized those values of multipurpose landscapes. She also learned that it’s critical to allow certain wetlands to follow their natural rhythm and go dry part of the year, to support the natural life cycles of animals and plants, including crops. “All of our melons and gourds and stuff like that used to be grown when the moisture is retained, but the surface flow is not there.”
In contrast, the British viewed land as property, so the commons, which could not be bought, sold, or built upon, “presented a very peculiar problem for them,” says Nityanand Jayaraman, who goes by Nity. A local community activist with a collective called Vettiver Koottamaippu, he works in North Chennai, where industrial facilities like coal plants are displacing fishing communities. “From a revenue point of view, it was wasteland.” As surrounding lands were developed, tension mounted over these two sets of competing values. “Of course, the old values lost,” he concludes. “And what we have is a disaster called Chennai.”
The lost values are arguably as significant as the declines in sustainable subsistence and healthy, functioning ecosystems. People’s identities are entwined with their place. When development annihilates a place’s natural heritage, people also suffer cultural loss—loss of identity. For example, Pallikaranai Marsh is home to neithal (Nelumbo sp.), an endemic, striking, blue-violet water lily, one of the earliest flowers described in Tamil literature, says Vencatesan. Other beloved creatures of the swamp include the glossy ibis (Plegadis falcinellus) and, perhaps surprisingly, the hump-nosed viper (Hypnale hypnale), one of India’s four venomous snakes. “Snakes are revered in Tamil Nadu,” says Vencatesan, who grew up in a neighboring state. “They think it’s a god, so, yeah, they have no problem with snakes.”
Today Chennai’s wetlands are still officially classified as wastelands, which has made Care Earth Trust’s progress thus far, conserving 620 hectares of Pallikaranai Marsh, all the more remarkable. The organization is also working to restore numerous other “wastelands” that are, or were, connected via water pathways to Pallikaranai. On a visit to a few of these sites with Care Earth staff, I see candle flower (Senna alata), a medicinal plant whose flowers exude a milk that soothes skin injuries, as well as bronze-winged jacanas (Metopidius indicus), fish eagles (Icthyophaga humilis), black bazas (Aviceda leuphotes), northern shovelers (Spatula clypeata), and many other native species.
At Thalambur Lake, we walk along a new levee that they pushed up with a bulldozer to keep water in the lake longer so that fish can lay eggs once again. The levee is pocked with young saplings of peepal and native bamboo. Looking down into the lowland, I can see the small islands they built and planted with trees to serve as nesting sites for birds.
At another spot just off of Mahabs Highway is a dock where you can rent paddle boats to explore Muttukadu Backwater, south of Pallikaranai. Dozens of pelicans sit on the water, bobbing on its calm surface. Here and in other neighborhoods near the ocean, excessive groundwater use has allowed seawater to push in, turning aquifers salty. Muttukadu has grown too salty for some of its native fish, and water levels have dropped. In response, Care Earth Trust has begun educating local people, petitioning the government to regulate water extraction, and restoring pathways to allow fresh water to flow into the wetland and replenish it. They’ve also started replanting mangroves to improve breeding habitat for fish.
To be continued next week…
Erica Gies is an independent journalist who covers science and the environment from Victoria, British Columbia, and San Francisco, California. Her work appears in the New York Times, Scientific American, Nature, Ensia, The Economist, bioGraphic, National Geographic, and other outlets.
Photographs by Dhritiman Mukherjee.
This story originally appeared in bioGraphic, an online magazine about nature and sustainability powered by the California Academy of Sciences.