Chennai needs an integrated water management system to prevent floods and drought: Dr S Janakarajan

Dr S Janakarajan recommends restoration of tanks and eris and creation of blue-green infrastructure to combat Chennai's water woes.

Chennai saw the flood of the century in 2015. Four years on, in 2019, the city came to a standstill as the main reservoirs ran dry and Chennai hit ‘Day Zero’. The city’s fraught relationship with water has affected the lives of millions with no permanent solution in sight.

In an interview with Citizen Matters Chennai, Dr S Janakarajan, the President of the South Asia Consortium for Interdisciplinary Water Resources Studies (SaciWATERs), Hyderabad and former Professor and Director at Madras Institute of Development Studies (MIDS), unpacks the issues with water management in Chennai that has led to both flooding and drought and suggests better ways to handle the city’s water resources.

Photo of Professor S Janakarajan
Dr S Janakarajan is the President of the South Asia Consortium for Interdisciplinary Water Resources Studies (SaciWATERs), Hyderabad. Pic Courtesy: Dr S Janakarajan

On floods and drought in Chennai

Chennai saw the worst floods in 2015 and ‘Day Zero’ in 2019. How are these two incidents connected and what is the lesson from these two incidents that Chennai has to learn?

Before actually going into that question, it is important for us to understand the definition of floods. The common perception is that any water stagnation – whether inside one’s compound wall or on streets and in a low-lying land – is considered a flood.

Hydrologically, flood is a flow concept. The flood would mean overflow of water leading to submergence; Overflow may occur from water bodies such as rivers and streams. Basically, floods occur when the precipitation exceeds the carrying capacity of rivers and streams. Floods can also occur from the sea – coastal flooding – reverse flow through backwater canals.

Floods can be categorised into two types, namely, fluvial (when the water overflows the riverbed as well as the floodplains) and pluvial (the one seen on the streets caused by inundation which could be caused by various anthropogenic reasons).

As far as Chennai is concerned, there is a third type of flood called coastal floods (caused due to high-speed winds, sea currents, growing activities along the coast and coastal erosion). Coastal flooding can also become more dangerous because of the climate change-induced sea-level rise. We should first be in a position to differentiate these three types of floods to plan the mitigation measures.

Read more: Urban floods: Why some areas in Chennai are worse hit than others

We all remember the 2015 floods since it has resulted in huge damage to lives and livelihoods, properties and so on. ASSOCHAM estimated the total loss due to the 2015 Chennai floods to the tune of Rs 20,000 crores. Compared to the 2005 Chennai floods, the 2015 floods are still remembered because there was a very heavy downpour for two days. The occurrence of rainfall on a single day exceeded what the city could carry naturally.

A rapid degree of urbanization is the key. As far as urban flooding is concerned, the impact of flooding will be felt more even when there is less rainfall due to swift urbanisation, resulting in high population density. Such rapid urbanization has resulted in the loss of pervious surface in most of the areas in Chennai. As a result, the per capita drainage space is becoming less with every passing day and the surface runoff has increased to over 90% in Chennai.

Floods as an issue should not be treated in isolation. We should understand the relationship between floods and droughts. An integrated perspective of the water management system is the need of the hour. It simply means integrating flood and drought with a view to mitigating both floods as well as droughts. When you take measures to mitigate floods, it should automatically take care of the drought and vice versa.

Water storage capacity in Chennai

The 2019 water shortage is said to have occurred as the reservoirs ran dry. Do you think the existing reservoirs have sufficient storage capacity for the city’s current and future population? How can the capacity of the existing reservoirs be increased?

The fundamentals of Chennai should be understood first. Very often when we speak about the water crisis in Chennai, we discuss reservoir capacity. However, there is little discussion on the rainfall pattern and the rainfall conditions.

When you look at Chennai’s rainfall data for the past 50 years, the city has received less than 1,000 mm of annual rainfall only for around 10 years. There was more than 1,000 mm of annual rainfall during the rest of the years. When we include the rainfall that is received in the neighbouring districts that fall under the Chennai Metropolitan Area (CMA), the average annual rainfall will be around 1,400 mm.

Have we made efforts to save this rainfall? Even when there is continuous rain for one full day, people are panicking that their homes will be flooded. The problem precisely lies here.

The key issue is how to save/conserve water in such extreme weather conditions. When we think about increasing the capacity of the reservoirs, we only think about increasing the capacity of the existing major reservoirs like Chembarambakkam, Poondi, Red Hills and Cholavaram. Of course, there is a huge possibility of increasing the capacity of these reservoirs by desilting, dredging and deepening.

However, in addition to that, we do have a large number of eris / tanks. According to the available records, there are over 3,600 waterbodies in the adjoining three districts of Tiruvallur, Kancheepuram and Chengalpattu. Each of these tanks is a watershed and hydrologically well connected.

Why is that we are not taking measures to desilt and deepen these tanks so that when there is heavy rainfall, these tanks can automatically get filled to save water? When water during rainfall months gets stored in these upstream waterbodies, the flow of water (floods) to the downstream will be reduced considerably.

Read more: City of 1000 Tanks unveils vision for a water-rich Chennai

The newspaper reports suggested that during the 2015 floods around 300 thousand million cubic (TMC) feet of water were drained into the sea. Why were we unable to save at least a part of such a huge quantity of water in these upstream waterbodies? Instead, 2016 was considered a drought year!

While there is plenty of scope for increasing the capacity of the four large city reservoirs, the focus should also be put on the restoration of other smaller waterbodies to conserve water. Such a measure will help a great deal to recharge groundwater and will help to create flora – fauna and microclimate and the related life system. Most importantly, the drinking water needs of the local area can be easily met.

Given that these waterbodies once functioned in a cascade system, steps should also be taken to find the missing interlinks and restore them. This will help in saving the surplus water from one tank by naturally making it flow to the downstream tank. Besides, Chennai, being a coastal city, is linked to the upstream river basins.

There are four major rivers flowing through the city of Chennai – Arniyar – Kosasthalaiar on the north, Cooum river on the Centre and Adyar on the South. Further south, we will find the Palar River carrying flood flows during the monsoon months. Besides, the Buckingham canal flows from north to south cutting across all these rivers. This is the unique system of urban rivers that the city of Chennai is blessed with, because of which Chennai should not suffer from floods.

The predictions made by the state government say that the annual demand could gradually rise to 32 TMC ft of drinking water in the next 5 to 10 years with the projected population growth. One of the solutions proposed is the creation of new storage structures. Do you think this is practically possible given the rapid urbanisation and the role of land occupation?

Instead of creating new reservoirs, the existing thousands of water bodies should be restored to their original capacity. There are several tanks on the ECR and OMR stretches that spread across thousands of acres. If these are restored and utilised properly, they can be used to cater to the water needs of southern parts of Chennai.

Similarly, a sustainable urban drainage system, an important emerging concept, means that we should store the rainwater where it falls. Therefore, let’s not complain about water scarcity without restoring these waterbodies.

Given the fact that more than 90% of the surface in Chennai has become impervious, we should focus on creating blue-green infrastructure. As part of this, parks and playgrounds can be used as holding ponds during the monsoon months. There are also hundreds of temple tanks and small ponds that could be utilized to store water. Besides, Chennai also has Pallikarani marshland, which is covered under the Ramsar Convention. This has to be rejuvenated scientifically.  

This apart, as citizens, I think we all have a shared responsibility. Rainwater that falls on our plot of land and on our rooftop is our water. This is our responsibility to conserve that water, instead of letting it pass onto the streets and contributing to inundation (floods).

Read more: Where does the water in your tap come from?

Desalination plant and rainwater harvesting in Chennai

Chennai is getting its 4th desalination plant. The desalination plants are said to solve the city’s water crisis. What are your thoughts on this?

The first and foremost question in this regard is to ask whether the city of Chennai deserves desalination plants. Desalination plants are something that one should rely on when we run out of all other options like that of the Middle Eastern countries where there is scarce rainfall.

When we have an average rainfall of around 1,400 mm in CMA, why would we need a series desalination plant?

Desalination plants are lazy solutions proposed by those who have not made sincere efforts to address Chennai’s water crisis. This apart, the desalination plants come with their demerits of being ecologically unsound. It will contribute to the destruction of the coastal ecosystem.

For instance, a desalination plant of 100 MLD sucks in seawater 20 times its capacity. When the seawater is sucked in, all the other living beings including millions fishes and eggs are sucked in. When the seawater is processed, the effluent or what’s called brine is let out, which is highly saline. If the total dissolved solids (TDS) levels of normal seawater are between 15,000 parts per million (ppm) to 20,000 ppm, the TDS levels of the brine will be between 50,000 ppm to 60,000 ppm or maybe even more.

When the brine is discharged within a distance of one to three kilometres from the shore, where the fisherfolks usually go fishing, the region becomes highly saline making the sea a ‘dead zone’. Not only will the desalination plants kill the ecosystem of the sea but also affect the livelihood of the fishermen.

While I acknowledge that the need for drinking water in Chennai has to be met, I would keep the desalination plants as the very last resort. It can be relied upon only after exploring the other options.

Read more: High TDS in water supply affects Valmiki Nagar residents

Rainwater harvesting is one of the state’s flagship projects. How effectively do you think it has been implemented over the years?

Whenever we talk about rainwater harvesting, we only talk about rainwater harvesting in individual households. While harvesting rainwater at individual levels is very important, we should not keep romanticising it.

Many educational institutions, Universities, hospitals and government buildings in Chennai have big buildings on hundreds of acres of land. Efforts should be taken to harvest rainwater in these buildings to make them more self-sufficient in order to meet their water needs.

Why should these buildings depend on metro water when they can easily be self-sufficient?

As I mentioned earlier, there are thousands of waterbodies and temple tanks in and around Chennai which are considered traditional rainwater harvesting structures. Those waterbodies should be restored to serve their purpose.

Groundwater in Chennai

Studies show the high-level concentration of heavy metals in groundwater in Chennai. How important is groundwater in solving the water crisis?

Though the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) supplies water, over 40% of Chennai residents continue to rely on groundwater to meet their water needs. While groundwater holds such significance, it is worrisome to see that the groundwater is becoming unusable every passing day.

While industrial pollution plays a major role in groundwater contamination, recent reports show that many waterbodies in and around Chennai are filled with garbage. Some tanks have been dumped with bio-medical wastes.

To preserve the groundwater, the sources of pollution like the discharge of industrial effluents and disposal of solid and bio-medical wastes into the waterbodies should be stopped immediately.

No matter how big or small the water body is, efforts should be made to restore it. Creating and maintaining the blue-green infrastructure can only help in recharging the groundwater and diluting the contamination.

Do you think stormwater drains hamper groundwater recharge?

The problem with stormwater drains (SWDs) is that it is used for dumping sewage. As a matter of principle, SWDs should carry only stormwater during monsoon months. They are misused even in the core areas of Chennai city and more so in the adjoining area which was annexed to the Greater Chennai Corporation in 2011.

This is a huge contributor to groundwater contamination in Chennai and has the potential to become a much bigger menace. It needs to be handled very carefully and that is where the GCC and the CMWSSB have to work together to have a scientific design of the sewage system as well as the SWD system to ensure the sewage and the stormwater are carried separately.

Read more: Looking beyond stormwater drains to realise the dream of a flood-free Chennai

Packaged drinking water plays a huge role in groundwater extraction in Chennai. Do you think there are strict enforcements on these companies?

There are regulations on paper which mandate licenses for these packaged drinking water companies. As I gather, many small companies continue to operate without licenses. There are also standards for safe packaging and transportation of water.

However, we see on a daily basis that these water cans are carried in the scorching sun, while they are supposed to be transported in a sheltered vehicle. This will develop microorganisms in the water which will cause health issues, besides contributing to microplastic contamination in the water.

Further, there is no limit set by the government on the extraction of groundwater for these companies. This contributes to the depletion of groundwater. The discharge of effluents into the ground also contaminates the groundwater. The issue here is that the people got very used to these packaged water supplies.

If the government tries to bring strict enforcement on these companies, the people will protest as they end up having no other source of, what is perceived as “clean and safe water”. As a result, the government will be forced to relax the regulations. However, more attention needs to be devoted to regularising these companies.

Studies show that of every Rs 10 earned per day by a poor person Rs 1 is spent on drinking water. With access to clean drinking water being a constitutional right of every citizen, how do you think the government can intervene here to offer that?

I agree that as a matter of principle, the government should be able to supply clean and safe drinking water to everyone. But in reality, the water is neither drinkable without further processing like filtering and boiling nor is it supplied to all equally.

Recently I came across the news that an apartment complex in Chennai is spending around Rs 12,000 per day on buying tanker water. This means that they can afford to spend Rs 3.6 lakhs per month on water. Whereas, the vulnerable communities in the slum areas hardly could afford this.

Considering the cost recovery aspect for the CMWSSB, the dual rating can be considered as a solution. A base amount, which is the bare minimum, could be fixed for all. While the water can be supplied free of cost to vulnerable communities, it can be supplied at a higher rate for those who can afford it.

Meanwhile, we should also remember that the water supply infrastructure that we have at present is age-old and it needs to be completely revamped.

Solutions to improve water management in Chennai

What do you see as the solutions to Chennai’s drinking water crisis?

  • Store water where it falls
  • Ensure all the surface water structures/waterbodies are used to the fullest capacity – desilt, dredge and deepen water bodies in order to store excess water
  • Ensure that large institutions are made self-sufficient to meet their water needs through rainwater harvesting and recycling of the used-water
  • Harvest rainwater in individual houses
  • Increase pervious surface or what is called lung-space
  • Create more blue-green infrastructure
  • Ensure that wetlands (both coastal and inland) and rivers are restored and maintained properly
  • Focus on integrated water resource management.
  • Rely on desalination plants only after exploring all the aforementioned options

Also read:

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Similar Story

Cauvery index insights: Bengaluru’s peripheries and some central areas face water challenges

A ward level index evaluates Cauvery supply, incorporating groundwater, land use, 2011 population census and governance factors.

(In Part 1 of the series, data analysts explained how they arrived at a definition of water security and created a location-specific index. In Part 2, the analysts will explain the methodology used in estimating the use of the Cauvery index and how the results have been obtained) The variables (below) were indexed and weighted with the Cauvery index, which was prioritised due to its significant impact on Bengaluru’s water security. Groundwater and land-use indices, being interdependent, received equal weights, followed by the governance index. Here is a summary table: Parent IndexVariableWeight AssignedCauveryCauvery supply to Ward1GroundwaterBorewell Water supply (litres/person/day)Ward area…

Similar Story

Is your neighbourhood ‘water-secure’? This index could tell you

An analysis of Bengaluru water supply origin, quality, consumption patterns by area, recharge methods, and the responsible authorities.

Bengaluru’s water crisis hit new lows in March 2024, which led to disruptions in water supply. There are areas in the city where water supply is irregular, expensive and unpredictable, bringing the daily lives of many communities to a standstill. It was this issue that made us, as a group, tackle the issue of water security at the Bengaluru Water Datajam held by in March. The notion of water security is a tricky problem to address. It depends on multiple factors like ecological security, risk management of the city, to name a few (Aboelnga et. al., 2019). Therefore, we…