How Chennai, Among World's Wettest Cities, Ran Out of Water

Climate change is bringing rising sea levels and increased flooding to some cities around the world and drought and water shortages to others. For the 11 million inhabitants of Chennai, it's both.

India's sixth-largest city gets an average of about 1,400mm (55 inches) of rainfall a year, more than twice the amount that falls on London and almost four times the level of Los Angeles. Yet in 2019 it hit the headlines for being one of the first major cities in the world to run out of water-trucking in 10 million liters a day to hydrate its population. This year, it had the wettest January in decades.

The ancient south port has become a case study in what can go wrong when industrialization, urbanization and extreme weather converge and a booming metropolis paves over its flood plain to satisfy demand for new homes, factories and offices.

Formerly called Madras, Chennai sits on a low plain on the southeast coast of India, intersected by three main rivers, all heavily polluted, that drain into the Bay of Bengal. For centuries it has been a trading link connecting the near and far east and a gateway to South India. Its success spawned a conurbation that grew with scant planning and now houses more people than Paris, many of them engaged in thriving auto, healthcare, IT and film industries.

But its geography is also its weakness.

The cyclone-prone waters of the Bay of Bengal periodically surge into the city, forcing back the sewage-filled rivers to overflow into the streets. Rainfall is uneven, with up to 90% falling during the northeast monsoon season in November and December. When rains fail, the city must rely on huge desalination plants and water piped in from hundreds of kilometers away because most of its rivers and lakes are too polluted.

While climate change and extreme weather have played a part, the main culprit for Chennai's water woes is poor planning.  As the city grew, vast areas of the surrounding floodplain, along with its lakes and ponds, disappeared. Between 1893 and 2017, the area of Chennai's water bodies shrank from 12.6 square kilometers to about 3.2 square kilometers, according to researchers at Chennai's Anna University. Most of that loss was in the past few decades, including the construction of the city's famous IT corridor in 2008 on about 230 square kilometers of marshland. The team from Anna University projects that by 2030 around 60% of the city's groundwater will be critically degraded. 

With fewer places to hold precipitation, flooding increased. In 2015, Chennai suffered its worst inundation in a century. The northeast monsoon dumped as much as 494mm (19.4 inches) of rain on the city in a single day. More than 400 people in the state were killed and 1.8 million were flooded out of their homes. In the IT corridor, water reached the second floor of some buildings.

Four years later it was a shortage of water that made headlines. The city hit what it called Day Zero as all its main reservoirs ran dry, forcing the government to truck in drinking water. People stood in lines for hours to fill containers, water tankers were hijacked, and violence erupted in some neighborhoods. 

"Floods and water scarcity have the same roots: Urbanisation and construction in an area, mindless of the place's natural limits," said Nityanand Jayaraman, a writer and environmental activist who lives in Chennai. "The two most powerful agents of change-politics and business-have visions that are too short-sighted. Unless that changes, we are doomed."

Tamil Nadu, the state of which Chennai is the capital, predicts in its climate change action plan that the average annual temperature will rise 3.1°C by 2100 from 1970-2000 levels, while annual rainfall will fall by as much as 9%. Worse still, precipitation during the June-September southwest monsoon, which typically brings the steady rain needed to grow crops and refill reservoirs, will reduce while the flood-prone cyclone season in the winter will become more intense. That could mean worse floods and droughts.

The northeast monsoon officially ends in December, but this winter the heavy rain continued well into January, with Tamil Nadu receiving more than 10 times the normal rainfall for the month.  

"Such heavy rainfall was not normal when my parents and grandparents were young," said Arun Krishnamurthy, founder of Chennai based non-profit Environmentalist Foundation of India. "People here talk a lot about the weird weather, but they don't link it to climate change." 

Chennai is an extreme example of a problem that is increasingly disrupting cities around the world that are also grappling with rapid population increases. Sao Paulo, Beijing, Cairo and Jakarta are among urban centers facing severe water scarcity. "It's a global problem, not just Chennai," said Krishnamurthy. "We need to work together to ensure that we have a water-secure future."

The Tamil Nadu government says it's addressing the problem. In 2003, it passed a law requiring all buildings to harvest rainwater. The rule helped raise the water table, but the gains were soon eroded by a lack of maintenance, according to the Agriculture Ministry's Central Ground Water Board. Efforts to recharge groundwater have also struggled to offset the volume of water being extracted through boreholes. 

The Chennai Metropolitan Water Supply and Sewerage Board did not respond to questions about the issue. The Tamil Nadu Water Supply and Drainage Board did not reply to an e-mail seeking comments.

Shortly after 2019's Day Zero, Tamil Nadu Chief Minister Edappadi Palaniswami announced a public program that would include a "massive participation of women" covering everything from rainwater harvesting, water saving and the recycling and protection of water resources, along with studies on how to clean up the state's polluted rivers.

Until then, the government's strategy had centered around the construction of large desalination plants, a costly tactic more commonly associated with arid nations or islands with limited fresh water. The plants have been criticized for causing environmental damage and having a negative impact on local fisheries.

Now, the government is pursuing a new approach inspired by the city's past. The Greater Chennai Corporation is supporting an initiative called City of 1,000 Tanks, a reference to the ancient man-made lakes that were built around temples.

Supported by the Dutch government and the Asian Infrastructure Investment Bank, the plan is to restore some temple tanks and build hundreds of new ones with green slopes throughout the city to absorb and filter heavy rains, recharge the groundwater, and store water for use during dry months.

"Floods, drought and sanitation are all interlinked," said Sudheendra NK, director of Madras Terrace Architectural Works, which is involved in the project. "When a critical mass of people take up all this then a significant difference will be noticed and we will no longer be in crisis." He said it would take at least 5 years for the project to have an impact.

Meanwhile, Chennai continues to add a quarter of a million people a year, making it a race against time to curb the floods and water shortages.

"My fear is these things will happen more often in the future," said Mr Krishnamurthy. "We didn't learn the lesson from 'Day Zero.'"