Groundwater Table in Chennai – Time to realize and act

Dr. Srinivasan Gopalakrishnan

Depletion of groundwater in Chennai is occurring at an alarming rate and the situation is grave. The city’s metropolitan area, suburbs and the adjoining towns are facing a severe groundwater shortage every summer. According to a report, the combined storage in Chennai’s four water reservoirs: Chembarambakkam, Poondi, Red Hills and Cholavaram – recorded 833 mcft in March, 2019.  A fifth reservoir, which is commissioned at Thervoykandigai is yet to be made of full use to the general public. Areas where groundwater was available at 10 feet until two years ago has now dipped to 22 ft. This is a clear indication of indiscriminate drawing of groundwater through bore-wells by both CMWSSB and individuals. If this is the case of City areas, the state of the suburbs is pathetic. In areas such as Ramapuram, Porur and Mugalivakkam, the groundwater table has dipped and is available only below 350 ft, which, a decade ago was available at 40 ft. In case of Sholinganallur, the groundwater was available at 25 ft in 2005, which does not yield water even at 100 ft today (CPCB report, 2007).

The port city of Chennai needs 800 million litres of water a day to meet the demand for water, according to official data. At the moment, the government is able to provide only 675 million litres, according to the Chennai Metropolitan Water Supply and Sewerage Board. As per a report, there are 492 licensed water packaging units in the metropolitan area, Thiruvallur and Kanchipuram districts and 4000 private tankers fleeting within the city area. Due to frequent traffic snarl in major roads, increasing number of vehicles, urban agglomeration, increase of footfall in city buses and trains, vertical expansion of city area, there is rationed distribution of water.

A recent research by the Centre for Climate Change, Anna University has cited the shrinkage of agricultural land by 24% and wetlands by 33% over the last decade. Also, the reasons are expansion of highways, flyovers, airports and high-rises. Delimitation of city area and subsequent conversion of agricultural lands into residential areas and the competition / greediness of realtors literally bring the picture of monopolizing the groundwater using bore wells. Since the city is entirely dependent on ground water resources, it is replenished by rain water and the city’s average rainfall is 1276 mm. Water level varies between different regions, so as the water quality. The level of Total Dissolved Solids (TDS) ranges between 600 ppm to 1500 ppm. There is no significant recharge of groundwater in June and there is a rise in the level in the month of January.

Seawater intrusion

Groundwater constitutes a crucial, subsurface part of the terrestrial hydrological cycle that influences a host of hydrological, ecological and biogeochemical processes. Overexploitation of coastal aquifers leads to saline water intrusion as a consequence of drastic lowering of water table relative to the adjoining sea level (Sophiya and Syed, 2013, Steinich et al., 1998, Brehme et al., 2011). Seawater intrusion or the movement of seawater into the freshwater aquifer zone increases groundwater salinity, posing environmental impact globally. A study indicated that the seawater intrusion and mixing of saline backwater with freshwater. There is the influence of fertilizers and anthropogenic activities such as indiscriminate discarding of plastics. Another study indicates that during 1940 – 1970 the population of Chennai was around 7.49 lakhs (to be precise, in 1961). The storage capacity of Poondi, Redhills, Cholavaram stood at 5596 mcft. In 1970 – 2000, the population which stood at 38.43 lakhs in 1991, the storage capacity was increased to 1558 mcft; in addition to that, Chembarambakkam tank was commissioned with a storage capacity of 3645 mcft. This was the period during which seawater intrusion started in and around areas such as Minjur (2 km), Besant Nagar and in the southern areas in 1989 – 1999. Today the population of the city is 70.9 lakhs. Since there is no point in relying solely upon natural recharge of ground water, agricultural wells were hired even as far back as 2001. The intrusion of seawater extended from 9 km to 16 km in 2004. Seasonal sampling study of groundwater in various sites inside the city area indicated higher concentrations of sulphats, nitrates and total dissolved solids (Loganathan et al., 2011).

Fig 1

(Source: The New Indian Express, Chennai edition, 02/01/19, pg. 2)

Groundwater salinization is a common threat in coastal parts of the world (Gimenez – Forcada, 2014, Camp et al., 2014, Nair et al., 2016). Certain cost-effective methods to determine the seawater intrusion are available. But, the historically known method to analyze is the presence of high concentration of sodium, chloride and bromide in groundwater. Fluoride concentration is very tricky – higher concentration leads to dental fluorosis and lower concentration may lead to tooth decay (Brinda and Elango, 2013, BIS, 1993).

Plastic menace

Choked with plastic and garbage waste, city’s minor canals are deprived of free flow of water; discarding of plastics, along with diversion of untreated wastes into waterbodies result in piling up of wastes and wastewater stagnation. Niti Aayog’s Composite Water Management Index, highlighted that Chennai will run out of groundwater by 2020). Segregation of plastic wastes is the major problem in the city. Although there is a rule to segregate biodegradable and non-biodegradable wastes before discarding, only less than 5% of the total population follows it. Mere discarding of the plastics – be it toys, plastic covers, wrappers and other materials – wherever we find, will accumulate and by time, will choke the groundwater. Even though there are centralized dumpyards at Kodungaiyur and Perungudi, the corners of each and every road, at times seems like a dumpyard due to inefficient solid waste management. In spite of garbage bins, omnipresent with colours indicating the segregation of biodegradable and non biodegradable wastes, all are dumped resulting in waste piles that contribute to flooding during the monsoon.

Measures to restore groundwater

Setting a limit cap for digging of bore wells and cancellation of licences for those firms flouting the rules. Not only framing rules is a must, but implementing it with iron-hand is much more important. Declaration of Pallikaranai wetland as a no discard zone and no development zone. Probably the Pallikaranai wetland is the only surviving freshwater marsh in the city area. Indiscriminate dumping of solid wastes, discharge of sewage and dumping of construction debris has literally turned it into another dumpyard apart from Kodungaiyur and Perungudi. These toxic wastes intrude into groundwater and makes it impotable. Desilting of water reservoirs, strict banning of discharge of sewage effluents and effluents from tanneries, hardware and automobile industries. Judicial use of groundwater and banning of water-related recreational activities. Mandating every citizen to plant 100 trees per head throughout Chennai. Creation of multi-level committees to impose fines for those who draw bore water more than the prescribed level. Compulsory inclusion of ‘groundwater conservation and ethics’ in the curriculum in schools.

Endnote

Chennai city has got a very good heritage and prominent landmarks are the signboards of the city.  Of late, it has been running a cold streak, both in the case of getting committed lawmakers and co-operative law-abiding citizens, in the case of judicial use of water for drinking and other purposes. There has been time when the city depended upon water from shallow wells and tanks, with copious drinking water available throughout the year. Also, there have been reports of the Adyar, Cooum, Kortalayar rivers with undisturbed and unpolluted waterflow. But the story is different today. Unless we understand that water is for all and we should not monopolize it, there is a need to critically assess the water requirement of Chennai city and take adequate steps to meet it.

References

1. Central Pollution Control Board (CPCB) report (2007) – Status of Groundwater Quality in India – Part – I.
2. Sophiya M S and Syed T H (2013). Assessment of vulnerability to seawater intrusion and potential remediation measures for coastal aquifers: a case study from eastern India. Environmental Earth Sciences, 70(3): 1197 – 1209.
3. Steinich B, Escolero O, Marin L E (1998). Salt-water intrusion and nitrate contamination in the valley of Hermosillo and El Sahuaral coast aquifers, Sonora, Mexico, Hydrogeology Journal, 6: 518 – 526.
4. Brehme M, Scheytt T, Celik M, Dokuz U (2011). Hydrochemical characterization of ground and surface water at Dortyol / Hatay / Turkey. Environmental Earth Science, 63(6): 1395 – 1408.
5. Loganathan D, Kamatchiammal S, Ramanibai R, Santhosh J D, Saroja V and Indumathi S (2011). Status of groundwater at Chennai City, India. Indian Journal of Science and Technology, 4(5): 566 – 572.
6. Gimenez – Forcada E (2014). Space / time development of seawater intrusion: a study case in Vinaroz coastal plain (Eastern Spain) using HFE – Diagram and spatial distribution of hydrochemical facies. Journal of Hydrology, 517: 617 – 627.
7. Camp M V, Mtoni Y, Mjemah I C, Bakundukize C, Walraevens K (2014). Investigating seawater intrusion due to groundwater pumping with schematic model simulations: The example of the Dar es Salaam coastal aquifer in Tanzania. Journal of African Earth Sciences, 96: 71 – 78.
8. Nair S I, Brindha K, Elango L (2016). Identification of salinization by bromide and fluoride concentration in coastal aquifers near Chennai, southern India. Water Science, 30: 41 – 50.
9. Brinda and Elango (2013). Assessing the changes in groundwater quality around tanneries: the Chennai example (India). Understanding Freshwater Quality Problems in a Changing World. Proceedings of H04, IAHS-IAPSO-IASPEI Assembly, Gothenburg, Sweden, July, 2013, 361: 265 – 270.
10. BIS (Bureau of Indian Standards) (1993). Indian Standard Drinking Water Specification (First Revision), IS 10500: 1991, 1 – 8.

 

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