TNN | Dec 3, 2023, 06.36 AM 1ST
NEW DELHI: Delhi has been drawing more groundwater than it recharges since 2022. The Central Ground Water Board's assessment found that the total annual groundwater recharge decreased from 0.41 billion cubic metres (bcm) in 2022 to 0.38bcm in 2023, while the annual extractable groundwater resource available decreased from 0.37bcm to 0.34bcm.
"Of the 34 assessment units (tehsils), 13 units (38.2%) have been categorised as over exploited 12 units (35.3%) as 'critical, four units (11.8%) as ’semi-critical1, and five units (14.7%) as 'safe1. Similarly, out of 1487.6 sqkm recharge-worthy area of the state, 617.3 sqkm (41.5%) are under 'overexploited', 306.4 sqkm (20.6%) under 'critical' category, 233.7 sqkm (15.7%) under 'semi-critical' and 330.2 sqkm (22.2%) under 'safe' categories," the report stated. In central Delhi, Karol Bagh was 'overexploited' and Kotwali 'critical'. In east Delhi, none was assessed to be overexploited but Mayur Vihar fell in the 'critical' category. In New Delhi, Delhi Cantonment, Chanakyapuri and Vasant Vihar were 'overexploited'. In the North, Narela was 'overexploited' and Model Town, was 'critical'. In North-East, Yamuna Vihar and Karawal Nagar were 'overexploited'. In Shahdara district, Vivek Vihar and Shahdara were 'overexploited' and Seemapuri 'critical'.
In south Delhi, Mehrauli and Saket were 'overexploited', while Hauz Khas was 'critical'. In South-East, there were no 'overexploited' areas but Kalkaji, Defence Colony and Sarita Vihar were 'critical'. In the South-West, Kapashera was 'overexploited' and Dwarka 'critical". In the West, Rajouri Garden was 'overexploited' and Patel Nagar 'critical'.
An area is 'overexploited' when the extraction of water is over 100%, meaning more water is drawn out than recharged. Extraction between 100% and 90% is 'critical', while between 90% and 70% is 'semi-critical'. Less than 70% extraction renders the area 'safe'.
The report said overexploitation of groundwater resources could be due to region-specific reasons. The report said that Delhi was covered by diverse rock types of different geological ages from pre-Cambrian to Recent, and around 89% comprised alluvium, with groundwater tapped mostly through tube wells. "The north-western part
of the country has plenty of replenishable groundwater resources but because of the over-extraction beyond the annual groundwater recharge, many of these units have become overexploited," it stated, adding that some areas had recorded a rise in the water table.
"Yields of tube wells vary from 4 litres per second to lips in older alluvial deposits and from 25 lps to 55 lps in newer alluvium. About 11% of the state is occupied by quartzitic hard rock, where bore wells have a yield of 0.6 to 5 Ips," said the report.
The report, however, also stated that the situation of groundwater had also improved since 2022 in some areas like Najafgarh, which was listed under the ’safe' category in 2023 against ’semi-critical1 last year. Hauz Khas and Dwarka too showed some improvement, though they still fall in the 'critical category. They were in the 'overexploited' zone last year.
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