At the peak of the water crisis, Chennai Metro Water Supply and Sewage Board(CMWSSB) was supplying only 525 million litres a day (MLD) of water as against its capacity of around 830 MLD. “Chennai has no perennial rivers for regular supply of water, and with a high growth in population, managing resources is a challenge,” says T Prabhushankar, executive director of CMWSSB.
In 2011, the city area (Greater Chennai Corporation) was expanded a third time — to 426 sq km. The same year, Chennai’s population stood at 8.6 million, making it India’s fourth largest metropolitan city and the 36th in the world, according to Chennai City Resilience Strategy 2019, a strategy report developed by Chennai Corporation along with 100 Resilient Cities, a project initiated by the New York-based Rockefeller Foundation to help cities become more resilient to the physical, social and economic challenges of the 21st century.
Chennai's dependence on monsoons makes it vulnerable to droughts. While the average annual rainfall is around 1100 mm, the monsoon window is narrow, giving rise to a supply-demand mismatch. For example, rainfall in the city reservoirs’ catchment area was deficient by over 30 per cent in 2016 and by 27 per cent in 2018.
About 65 per cent of Chennai’s water supply comes from five reservoirs around the city, which have a combined capacity of over 12 TMC of water. Two desalination plants account for 16 per cent of the water supply, 10 per cent is recycled waste water, and nine per cent comes from groundwater.
Experts say that Chennai’s ground water is well nigh depleted. As much as 85 per cent of the ground water potential in and around Chennai has been extracted, reveals Balaji Narasimhan, professor, Department of Civil Engineering, IIT Madras.
“By 2030, the authorities may have to go as far as 250 km away from Chennai to extract water to meet the demand of 120 litre of water per capita per day,” says Umamaheshwaran Rajasekar, chair, Urban Resilience – 100 Resilient Cities, National
Institute of Urban Affairs, New Delhi, in a recent meeting on “Making Chennai Water Positive”, organised by the Madras Chamber of Commerce and Industry.
The demand for water for municipal and industrial use in Chennai is expected to be 2248 MLD in 2026 — up from the 1,797 MLD in 2016.
The 100 Resilient Cities strategy paper points to the lack of planning in land development in the past. Flood prone areas were marked only post the December, 2015 floods. In the late 1990s, the development of Chennai’s IT corridor along the eco-sensitive wet lands of the Old Mahabalipuram Road increased the risk of flooding there.
In addition to floods and droughts, Chennai is also at risk from earthquakes and the related risk of tsunamis. The city is also vulnerable to the risk of nuclear accidents, owing to its proximity to the Kalpakkam Nuclear Power Station. The Tamil Nadu State Disaster Management Perspective Plan 2018–2030 attempts to integrate disaster risk into policymaking and planning.
“The problem is the intensification of extremes of water cycles—producing both drought and flooding—and the increase in average global temperature, which is leading to a rise in sea levels. Other complications such as land subsidence and salinisation are the result of these,” says Andrew Rudd, urban environment officer, UN Habitat, India.
Unsustainable per capita consumption and extraction of water, mismanaged solid waste (a factor that contributed to the 2015 floods) are all causes of the droughts and flooding cycle that Chennai has seen in recent years.
However, there’s hope yet. Experts say that for the city to become drought resilient, it must adopt water reuse and recycling. “We have seen the water situation improving and we are identifying new water sources, such as old quarries where rainwater is collected and new bore wells. There are also plans to increase capacities for desalination and recycled water,” says Prabhushankar.
Rudd says regulating and reducing the per capita consumption of water and incentivising cyclical water collection methods such as rainwater harvesting are the need of the hour. However, this will mean behavioural changes, accepting personal and collective responsibility for unsustainable consumption, and generating the political will for systemic change.
The state government is planning to make Chennai the first city in the country to achieve 100 per cent reuse of waste water by 2025. The all-weather water supply source is expected to be 1150 MLD by then, with around 750 MLD coming from desalination, 120 MLD from tertiary-treated reverse osmosis (TTRO) and 280 MLD derived from tertiary treatment ultra filtration (TTUF).