Groundwater table rose by 3m in Nilothi, Najafgarh: Report on Delhi lakes
The Delhi government’s lake revival project, based on recycling treated wastewater, has been successful in southwest Delhi, where the groundwater table has increased by up to 6 metres in the last three years, a new study by the Centre for Science and Environment (CSE) has found. The study, which looked at successful lake rejuvenation models across the country, found the groundwater table had increased by around 6 metres at Pappankalan, by around 4 metres at Nilothi and by 3 metres and at Najafgarh through the artificial lakes created there by the government in 2021. The report, titled “Back from the Brink: Rejuvenating India’s Lakes, Ponds, and Tanks – A Compendium of Success Stories”, looked at around 250 water bodies from 22 different states. The report said that the idea in Delhi was to fill the water bodies with treated effluents. “To ensure that lakes and water bodies remain filled throughout in Delhi, which has just 50-odd rainy days a year, DJB connected the revived and new water bodies to the sewage treatment plants wherever possible,” said the report, adding that efforts have also been made to ensure high percolation into the ground. These efforts include adding a sandy layer at the base, particularly where clay content was high. The model highlights how Delhi created lakes next to existing STPs that treat the water at multiple levels before pumping it. Two lakes have been created near the Pappankalan STP, one next to the Najafgarh STP and three near the Nilothi STP. Though a lake has also been created next to the Dwarka STP, no groundwater data was available as a piezometer was installed only recently. “The lakes have been designed so that there is effective percolation into the ground. In Dwarka, clay and kankar form the top layer up to a depth of 4 metres below ground level, followed by kankar and silt up to a depth of 68 metres below ground level. The presence of clay in the subsoil can hinder percolation of water to below the ground. DJB worked on improving the percolation property of the soil, and the bases of the lakes were rectified by addition of a sand layer,” the report added.
