Illegal extraction and poor rainwater harvesting affect groundwater in Chennai

Residents rely heavily on groundwater across Chennai. However, efforts must be made to prevent over-extraction and contamination.

Take a drive along Keelkattalai to Kamatchi Memorial Hospital any time during the day, and you will see hundreds of water lorries parked on the radial road. This stretch, 80% of which falls under Kovilambakkam Panchayat and 20% within the Greater Chennai Corporation (GCC) limits, is a hub of illegal groundwater extraction — one of the root causes of Chennai’s water woes.

As it happens, there are four or five legitimate water drawing points near the Keelkattalai lake, but the lorries do not use those points to extract water. “A black hose has been laid illegally,  2 to 3 km away from the extraction point. The lorries now extract groundwater through that black hose near Nanmangalam Lake,” says S David Manohar, a social activist with Arappor Iyakkam.

Groundwater plays a crucial role in helping Chennai meet its water demands. Inordinate delay in creating infrastructure for piped water supply in many areas across the city has forced residents to rely increasingly on groundwater. A healthy groundwater table helps residents tide over droughts such as the one Chennai experienced in 2019. However, persistent issues involving illegal extraction in the outskirts of the city and also contamination have left residents in the lurch.

Read more: Chennai just got a new system to monitor groundwater levels. How will it help?

Illegal extraction of groundwater in Chennai

Illegal extraction of groundwater takes place mostly on the outskirts of the city. In the southern part of the city, there are three stretches from Pallavaram to Thoraipakkam, where illegal extraction of groundwater is common. 

The first area from Pallavaram GST road to Keelkattalai junction falls within the Tambaram Corporation limits. The second, where extraction is most common, is the one mentioned above —from Keelkattalai to Kamatchi Memorial Hospital. The third area is from Kamatchi Memorial Hospital to Thoraipakkam and falls within the Greater Chennai Corporation limits. 

“The road used by the lorries that draw water near the Nanmangalam Lake, which ends up being damaged, falls under the jurisdiction of the Highways Department. The area falls under the Tambaram Corporation and the lake in question falls under the jurisdiction of the Public Works Department. While most of these lorries are private, some are also contracted by the CMWSSB. Thus it becomes an interdepartmental issue,”  says David, adding that there is no written communication regarding this issue between various departments.

Notably, private lorries supply water across Chennai Metropolitan Area while the CMWSSB lorries supply water only to areas under GCC limits. 

The CMWSSB officials say that they have taken measures to curb illegal extractions within its jurisdiction (GCC limit) and have authorised filling points across the 200 wards. The lorries can fill water only from these points and there is no way for illegal tapping from these places.

Contradicting the official’s statement, a metro water lorry driver says, “We take water from the filling points authorised by the CMWSSB. There are also limitations on how many trips each lorry can take but if we pay extra to the staff at the filling points, they might allow us to take extra water.”

“The crux of the problem lies in extracting more groundwater than is recharged. The loss of percolating space due to rapid urbanisation prevents groundwater recharge,” says Darwin Annadurai, a resident of Chitlapakkam.

Groundwater pollution and supply irregularities

Residents of Perungudi say that the groundwater in their locality is extremely polluted due to the nearby dump yard. The leachate from the dump yard has started to stagnate and seep into the ground, causing health hazards to the residents. 

V Srinivasan, a Member of Save Pallikaranai Marsh Forum, says that the government has totally abdicated its responsibility to supply drinking water in areas like Perungudi, Thoraipakkam and Sholinganallur. Recently hundreds of residents in Sholinganallur staged a protest demanding the government provide drinking water and sewerage connection.

“All these areas depend on tanker lorries to supply water. The residents have to book tankers for regular use. There is no initiative from the government to supply water voluntarily,” he says.

The metro water lorry driver says that they supply water in lorries to those residents with sump connections who complain that they have not received water through the pipeline.

During drought, the CMWSSB supplies water through tankers to localities where there is water scarcity.

On average, residents in an apartment in OMR spend around Rs 3,500 per month on water supply and sewage disposal. While the residents complain of inaction by the government in ensuring a regular water supply, ironically, this is also a part of the city from which many tanker lorries allegedly extract groundwater illegally.

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

Monitoring mechanism of CMWSSB

Incidents and complaints such as the above naturally raise questions about the efficacy of CMWSSB’s monitoring and redress mechanism. 

As part of the comprehensive automatic groundwater monitoring system that was implemented in 2021, the Board installed 200 groundwater monitoring devices and 20 rain gauges across 15 zones of the city. 

This initiative was aimed at assessing the groundwater level across Chennai and taking proactive measures accordingly. For example, increasing water supply to a particular area when the table dips and curbing the over-extraction of groundwater in such areas.

“Based on the data from the devices and from the data on water quality from our labs, we have been restricting water supply in a few areas and increasing the supply in other areas,” notes an official of the CMWSSB, adding, “Whenever we receive complaints, we conduct an inspection. If it is found to be an unauthorised extraction, we seize the materials used for the extraction of groundwater and take the necessary action”. The data from the monitoring devices is made available online, it can be used by the residents to keep track of it and also take necessary measures to conserve water. 

“If the Board has been using the data to assess the groundwater levels and quality, it should have reflected in their actions including regularly supplying water to the residents before they book a tanker lorry. This only seems like a bureaucratic practice done to gather data for internal purposes,” says Srinivasan.

It is to be noted, however, that the jurisdiction vested with CMWSSB is only 426 square kilometres. There are 302 revenue villages in the CMA which come under the jurisdiction of the concerned Revenue Divisional Officers.

“It is up to those officials to implement the Chennai Metropolitan Area Groundwater (Regulation) Act, 1987,” adds the official.

Improving Chennai’s groundwater levels

Following a severe drought between 2001 and 2003, then Chief Minister J Jayalalithaa passed an Ordinance in 2003, mandating all buildings in Tamil Nadu to create rainwater harvesting structures with immediate effect. The ordinance had a positive impact on groundwater levels in Chennai in the following years, proving the need to embrace rainwater harvesting widely.

Based on the data from the monitoring system, the CMWSSB conducted a survey across all the buildings in Chennai within the Greater Chennai Corporation limit in 2022. It was found that 68% (around 7 lakh buildings) of the buildings have functional rainwater harvesting structures. Over 1.85 lakh buildings have rainwater harvesting structures which have not been maintained. 

“We have insisted these buildings maintain the structures to conserve groundwater. The other buildings that do not have rainwater harvesting structures fall under the areas annexed to GCC in 2011. As we are creating infrastructure now for them, we have also urged them to build rainwater harvesting structures,” says the CMWSSB official.

CMWSSB's Monitoring and Control Centre
CMWSSB tracks the movement of the water lorries in its jurisdiction through GPS trackers from the Monitoring and Control Centre. Pic: Shobana Radhakrishnan

On curbing the operation of illegal tankers, especially those contracted to the CMWSSB, the official says, “There are 548 water lorries and 46 filling points in the operational area of CMWSSB (GCC limits). GPS trackers are fixed in these lorries to track their locations and also to measure the quantity of water dispensed from them.”

“The lorries are tracked from the control room in the head office of Chintadripet. Before the GPS trackers were installed, there were some irregularities. For instance, we were unable to track if the quantity of water ordered by the residents and the quantity of water dispensed from the tankers were the same. With the GPS tracker, we can keep track of the quantity. Similarly, as the lorries are tracked in real-time throughout the day, there is no way for them to go off the assigned route or be involved in irregularities,” says the CMWSSB official.

“Sometimes, even after the contract period is over, the lorries will not remove the mention of CMWSSB on them. When these lorries extract water illegally and supply the same privately, we have no control over them,” he adds.

“The government can supply water from the desalination plants to the private tankers at a fixed rate to prevent the illegal extraction of groundwater in the outskirts of the city,” suggests David.

Better coordination between agencies is critical for cracking down on illegal extraction and fixing groundwater issues. As is the adoption of rainwater harvesting on a larger scale.

With the vagaries of monsoon dictating water supply, making the most of the rainfall received and introducing stringent checks and balances on the judicious use of groundwater have to be ensured in Chennai without any delay. 

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