Groundwater in Delhi is depleting so fast that the national capital may run out of it by 2020. The assessment, damning as it is, was made by the Niti Aayog, the central authority mandated to put the nation on a growth trajectory, in a recent report.
A recent study commissioned by the National Geophysical Research Institute (NGRI) also painted an alarming picture, saying groundwater levels in the city are vanishing at an astonishing rate of 10 cm every year. With its air already laced with toxic poison and groundwater sources drying up, the city not only risks slipping further down on the livability index but also sending its residents scrambling and scrounging for every drop in the not too distant future.
The depth of water below the surface varies in different parts of the Delhi, largely due to geological factors and proximity of the source to the Yamuna. While in some parts, such as those in the vicinity of the Yamuna flood plain, groundwater could be reached barely 1.2 metres below the surface, in others, particularly to the south of Delhi Ridge ground, it could be as far as 64 metres below the ground, according to a study by Central Ground Water Board (CGWB).
“With the demand for groundwater on the rise to meet the needs of the rising population, more water has to be extracted. The situation is the same in Delhi as it is elsewhere. A CGWB report on Delhi says vast swathes of the city, barring some parts, are battling groundwater deficiency. However, the Board does not have data on how much groundwater is extracted. However, what’s plain to see is that lakes and other groundwater sources are drying up or are being encroached, and, unless revived, the city will struggle for every drop,” Sushmita Sengupta, programme manager, Water Programme, Centre for Science and Environment (CSE), said.
To put a leash on rampant, often illegal, extraction of groundwater, the Delhi government recently sealed unauthorised borewells across the city in line with a directive from the National Green Tribunal (NGT).
Government effort
Chief Minister Arvind Kejriwal, also the chairman of Delhi Jal Board (DJB), is seized of the city’s groundwater deficiency and depletion, and has laid out a revival plan through rejuvenation of dying lakes and other water bodies.
The DJB, too, has held out an optimistic take on the city’s groundwater scenario, saying that water bodies on its watch, which have a combined holding capacity of 135 million gallons, will cover 350 acres of the city in the forseeable future.
“No time limit can be set for such projects. The groundwater situation will improve gradually. It is a continuous process. In many areas (of Delhi), the groundwater levels are already showing signs of improvement. If we can provide potable water to the people, they won’t feel the need to turn to illegal extraction. This is precise what we are working at. If we can curb extraction, it will help maintain the city’s groundwater balance,” Dinesh Mohaniya, vice chairman, DJB, said.
The DJB has divided its groundwater revival work into four steps. First is revival of dying lakes and abandoned pits by relaying them in a manner that helps boost the groundwater level. It also includes digging more canals. Second is the Palla project, which is aimed at holding the city’s rain run-off on the Yamuna flood plains. Third is rainwater harvesting and fourth, drain water harvesting.
Lakes, canals, pits
Faced with limited raw water sources and rising demand to meet household, commercial and industrial needs, the DJB started working on a plan to use treated effluent water as a source to recharge the groundwater levels in an environmentally sustainable manner. It has also been working simultaneously on reviving the city’s lakes, canals and abandoned pits.The first effort to that end was the revival of the Rajokri Lake in 2018.
Relaid at a cost of Rs 222.10 lakh, the dying water body was fed with wastewater discharged from surrounding areas using SWAB technology. The area around the lake has seen a wave of landscaping and beautification — with the setting up of a Chhat Puja ghat, an amphitheatre and walkways to encourage community participation in keeping the lake in good order.
“The water bodies currently in Delhi are of certain types — totally dry, sewage-contaminated, filled with rain water, minor contamination or totally clean. Satpula, Ghoga and Roshanara, which are among the dry lakes, have been treated using the same mechanism. The ones that are full are pumped dry before being filled with treated water using a natural technique,” Ankit Srivastava, technical advisor, DJB, said.
In bigger lakes where the water cannot be pumped out, the DJB is using the Decentralised Sewage Water Treatment Plant (DSTP) tech to re-circulate existing water.“Fifteen days of rainfall isn’t enough to revive groundwater in the city. We have to think of alternatives, one of which is to use treated water,” Srivastava said.
The DJB is also working on reviving old canals. Srivastava said a 4-km-long abandoned canal in Northwest Delhi has identified for revival. It will be filled with flood water from the Yamuna, he said.
“There are many canals, like the one at Auchandi, which receive water from Haryana for irrigation. The DJB has given its nod to replacing canal water with the one from sewage treatment plants. As much as 51 cusec will be used for drinking purpose,” he said. In other minor canals, the DJB plans to install DSTPs such as the one in Mungeshpur drain, which can clean sewage water from villages. In Mundka, Najafgarh and West Delhi, irrigation minors will be soon get clean water.
Palla Project
One of the government’s pet project aimed at recharging groundwater sources, the Palla Project aims at holding rainwater in the Yamuna floodplains in a giant reservoir between Palla and Wazirabad. As part of the project, small ponds will be dug to hold water from an overflowing Yamuna during the monsoon season. A pilot project was implemented last year and the DJB claimed that a report has shown amarked improvement in the groundwater level. Spread over 18 acres, the ponds received flood water from the Yamuna for 12 days.
Rainwater harvesting
As per government rule, rain water harvesting (RWH) has been made compulsory in government buildings, schools and housing societies. The role etched out for the DJB in this direction is to provide financial support of upto Rs 50,000 for installing such systems and also help with technical assistance, empanelled agencies and simplified designs.While 80 per cent of government buildings and schools have installed RWH systems, the DJB said the response from housing societies hasn’t been as encouraging.
Drain water harvesting
Initiated as a pilot project in East Delhi, the DJB and Irrigation and Flood Department have deployed a ‘drain water purification system’ in Shahdara link drain near Akshardham, using electrocoagulation technique to purify sewage water.Initial estimates suggest that the plant can filter and supply 4 million gallons per day of drinking water in East Delhi, as well as help groundwater recharge in adjoining Noida.The DJB is also experimenting with Geotextiles bag to clean the drains. The bags are mostly used in stopping erosion of river banks. Made of polypropylene or polyester, Geotextiles are permeable fabrics having the ability to filter drain sludge.
Technology Used
The technologies being put to practice to revive groundwater are Phytorid technology, developed by National Environmental Engineering Research Institute (NEERI) and the DJB’s SWAB. “Phytorid and SWAB are natural and cost-effective ways of treating water. But in cases where these techniques can’t be applied, we rely on electromechanical pumping,” Srivastava said.
Quality of Soil
Soil infiltration is the process by which water on the surface seeps into the ground. In Delhi, the soil quality is mostly light with subordinate amount of medium texture soils. While the Yamuna has sand pit on both sides — 4 to 5 km wide and 40-50 feet deep, the Asola Bhatti Mines is rocky. The one in Dwarka is mixed with silt and pebble, making its soil strata percolation rate different than others.
Challenges
Srivastava noted the technical challenges faced by the DJB, topping which is the non-availability of a specific guideline. “There’s also a lot of inter-disciplinary work involved and currently, we don’t have enough engineers,” he said. He also cited encroachment, resistance from locals and socio-economic issues.
Projects on anvil
A 10 MLD effluent pumping station at Okhla STP, estimated at Rs 44.57 crores. From the STP, treated effluent water will be supplied to fill the abandoned mining pits of Bhatti mines through a 27.5-km pipeline. Project tipped to increase the groundwater level in the Chhattarpur Assembly constituency as well as nearby Sangam Vihar, Deoli, Mehrauli and Ambedkar Nagar constituencies
DJB to rejuvenate water bodies in its control and beautify 4 of them using Phytorid treatment technology, of capacity 300 KLD each, at Rasulpur, Bindapur, Dhinchaukalan and Tikrikalan. These water bodies will recharge the groundwater levels in these areas
DJB to develop 25 MLD naturally sustainable wastewater treatment plant in the defunct oxidation pond, of 35 ML capacity, near a 6-acre lake. It will also set up a biodiversity-cum-wetland park at Timarpur
