The Sunday Deep Dive

Water sources aplenty, but Chennai still thirsty

Come March, the line-up of lorries at filling points gets longer as the demand for water soars. Recently, a strike by tankers created panic among residents of South Chennai.

Come March, the line-up of lorries at filling points gets longer as the demand for water soars. Recently, a strike by tankers created panic among residents of South Chennai.

A three-day strike by private water tankers earlier this week held parts of South Chennai to ransom as it paralysed the entire IT Corridor that went dry within two days. Residents were pondering over shifting to other localities and IT companies threatened to close down operations as there was acute water shortage.

Though the issue between private water tankers and the Kancheepuram district administration on provision of licences for drawing groundwater remains unresolved, lorry operators finally yielded to public pressure and resumed operations.

For a city that gets an average rainfall of nearly 140 cm, every summer is a struggle and water managers wait with fingers crossed for the Northeast monsoon to fill the reservoirs. The failure of monsoon to provide adequate rain just once, as in 2016, is enough to trap the city in a vicious water crisis.

And not just this. Chronic water shortage in a city surrounded by three major waterways — Cooum, Adyar and Buckingham canal (now mostly reduced to sewage carriers) — and thousands of waterbodies in neighbouring districts is ironic, and reflects the degenerating impact of urbanisation over the city’s natural resources.

 

Disused and misused

S.Janakarajan, president, South Asia Consortium for Interdisciplinary Water Resources Studies, says, “There are nearly 3,600 waterbodies in Tiruvallur, Chennai and Kancheepuram districts. If maintained properly, nearly 80 tmcft of water could have been stored during floods. The reservoirs that cater to the city have only a capacity to store 11 tmcft.”

Citing the long process of creating new reservoir in Thervoy Kandigai Kannankottai, Tiruvallur district, Prof. Janakarajan says it would need immense effort and a huge amount of funds to create new lakes. Pointing out that the city received more than the average rainfall during half the period in last five decades, Prof. Janakarajan said: “It is high time we respect monsoon, understand its characteristics and plan accordingly by preserving water bodies.”

Here’s an interesting statistic: nearly 300 thousand million cubic feet (tmcft) of water is estimated to have drained into the sea through various waterways during 2015 floods. Water experts point out that could have been saved and used in times of crisis had we taken care of the waterbodies in and around Chennai and its neighbouring districts.

They note that extreme weather resulting in floods or drought must be expected and used as an opportunity. Drought is the best time to desilt waterbodies. Prof. Janakarajan charges that successive governments for the past few decades have neglected waterbodies, leading to their systematic destruction and groundwater depletion.

Calling the major waterways city’s arteries, he said the long-standing dream to restore them may come true when the government and residents take a collective responsibility to arrest sewage flow into rivers. The survey and settlement registers during the past century may be referred to for the restoration of the rivers’ original width, he added.

Scarcity already

This year, the scramble for water has started much earlier than usual as Chennai district ended with a 57 % deficit in Northeast monsoon rain in 2016. While Chennai Metrowater is planning to tap water from new resources, abandoned quarries or agricultural wells and smaller water bodies, residents are already thinking of sinking deeper borewells.

While it is deemed convenient to believe that Chennai is traditionally a rain-starved city, meteorologists note that the water scarcity is more of human-induced, as the annual rainfall has been less than 100 cm only on a few occasions since 1969.

Y.E.A.Raj, former Deputy Director General of Meteorology, Chennai, explains that the average yearly rainfall for the city has been recently recalculated and increased to 140 cm from the earlier 125 cm owing to the copious rainfall in the recent decade.

“The city significantly witnessed water crisis during 1974, 1982, 1986, 1992 and 2003 when it received an annual rainfall of less than 100 cm,” says Mr. Raj. Strangely, Chennai suffered a water crisis in 1992, even though it received 118 cm of rainfall, as it did not rain over catchment areas of city reservoirs. If the annual average rainfall crosses 100 cm, it is considered good as it is still higher than the average rainfall of some of the cities like Delhi and Pune that receive less than 80 cm.

Mr. Raj recalls that though the trend of apartment complex had not caught up with the city then, people were scrambling for water as shallow wells had dried up. “It paved way to the practice of sinking deep borewells when the State government sunk borewells along Rajiv Gandhi Salai,” he added.

According to UN-Water, about 50% of the world’s population live in cities and this is bound to increase to 70% by 2050. The global water demand too is set to go up by 50 % in two decades.

The recent strike in South Chennai has also brought to the fore key issues of haphazard urbanisation with least importance to urban ecosystem management. Experts and residents raised concern over permitting high-rise apartment complexes and gated communities without proper infrastructure. G.Sathish of Semmenchery suggested that building plan approval must be provided to those large commercial buildings and apartment complexes that show a water source to cater to the demand of residents.

Storage capacity

The city loses much of precious resource and reels under perpetual water crisis every summer as it lacks the capacity to store water. “The dry Poondi and Cholavaram reservoirs could be deepened to increase their capacity by 5-10 %. The tanks between the stretch of Chembarambakkam and Kaveripakkam could be improved and used for city supply,” said R. Emaraj, Engineer-in-Chief, Water Resources Department.

Recalling a proposal to bring 12-15 tmcft of water from a distant source, he suggested that the government accelerate the project to lay a direct pipeline to transmit surplus water from Mettur dam. While it is important to regulate groundwater extraction for commercial purposes, the practical difficulties in providing licences must be looked into, he said.

Grey water recycling?

Any attempt to restore the city waterways is futile, as has been proved, unless raw sewage flow is arrested and a comprehensive sewer network is in place. Though water from waterways cannot be used directly, they would be a good source of groundwater recharge, note experts.

The tendency to treat sewage as an unpleasant problem must change and the concept of sewage as a resource must be popularised. This year’s World Water Day that falls on March 22 is a timely reminder to improve water resilience and UN-Water’s theme on waste water suggests various means of waste water management.

“Chennai generates nearly 700 million litres of sewage daily. This could be recycled through decentralised treatment plants. It would work out cheaper at ₹28-30 per kilo litre than the desalinated water that costs ₹48 per kilo litre. The sludge could be converted into bio manure,” suggests Prof. Janakarajan.

RWH more relevant

According to Sekar Raghavan, director, Rain Centre, it may sometimes become difficult to harness the entire volume of rainwater during monsoon as the water table fast reaches its saturation level. “We can harvest at least 80% of rainwater when the water table is low during summer. It is important to invest in rainwater harvesting according to soil conditions. For instance, places like Taramani, Chromepet and Anna Nagar that have clayey or rocky soil conditions, permeability is less and water soon flows out. Water spreads like roots in sandy areas like Besant Nagar,” he says.

The tanker strike seems to have turned the attention towards rainwater harvesting in areas along IT corridor. “It is difficult to revive deep aquifers tapped by borewells. But, shallow aquifers would come alive in a year or two. Summer harvesting is the best option for coastal areas like Sholinganallur as it would push the saline water table down. Besides creating sumps of large capacity to store rainwater, residents may go for 10-15-feet deep shallow wells to draw fresh water and supplement their needs,” says Mr. Raghavan.

While a myopic agenda might well be the tool to address the immediate water needs of residents, Chennai, despite its vast wealth of natural resources, will remain a water-starved city unless long term and sustainable solutions are developed.


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Printable version | Jun 29, 2022 10:42:48 pm | https://www.thehindu.com/news/national/tamil-nadu/water-sources-aplenty-but-city-still-thirsty/article61804445.ece