Here, surely, is a disaster in the making. Bangalore is using up much more water than it is recharging.
According to a 2010 study by Karnataka Groundwater Authority members, the city is recharging only 3,290 hectare metres of groundwater annually even as it exploits three times more than the recharge for various purposes.
The study reveals that apart from a steep increase in groundwater exploitation in Bangalore in recent years, there is also a considerable amount of wastage—which can be avoided if water is used and preserved judiciously.
“Bangalore is [spread over] an estimated 800 sq km,” says KC Subhash Chandra, hydrologist and groundwater expert member, Karnataka Groundwater Authority. “Of this, the built-up area is 560 sq km, with 240 sq km of open space. Naturally, there is a severe restriction of rain water infiltration into the ground.”
The study shows that only 6% of rain water is materialising into groundwater in the open areas.“Over 17,040 hectare metres of rain water is being wasted by being drained along with sewage water,” he says. “This is clean water that can be used.”
According to the study Bangalore receives 830 mm of rainfall annually, which amounts to 66,400 hectare metres of water. “Over 71% of the water is getting wasted in evaporation and transpiration,” Chandra says. “If the rainwater that is being wasted as run-off, amounting to 17,040 hectare metres, is saved and used, it can serve 23 lakh people—about 24% of the city’s population.”
The Bangalore Water Supply and Sewerage Board (BWSSB) supplies 35,605 hectare metres of water to the city. “According to BWSSB data, the population will increase to 95 lakh in 2020, and the requirement of water will go up to 48,600 hectare metres,” Chandra says. “How will they increase to this number? Only 27 hectare metres of water is being added to the Cauvery Stage IV now. This will not suffice in another 10 years.”
Bangalore is currently facing a shortage of 11,226 hectare metres of water.