'Rainwater, treated sewage water can quench 50 lakh people's thirst'

He was delivering a lecture on ‘Demand, resource availability and status of drinking water supply to mega city like Bangalore,’ at the Geological Society of India here on Wednesday.

Chandra said precious surface water of nearly 17,040 hectare metre per year was getting drained along with sewage water. If this water is adequately conserved, it alone can meet the requirement of about 24 lakh people.

If the total sewage load of 26,316 hectare metre per year generated in the City can be treated up to tertiary level and brought to safe standards and drinking water-usage and even if 50 per cent of treated water is put to use, it can serve 26 lakh people.

Options like rainwater and treated sewage water are more economical than anti-environmental proposals - like diversion of water flow to the City from west-flowing rivers like Netravathi in Western Ghats, or tapping water from distant river system, that are on the anvil,” Chandra added.

No realistic data
Explaining about the exploitation of groundwater, Chandra said Government institutions or agencies have no realistic statistical data on the number of borewells sunk in the City and the quantity of groundwater being extracted from aquifer.

The Bangalore Water Supply and Sewerage Board and the Bruhat Bangalore Mahanagara Palike, along with private drilling agencies have revealed that there are nearly 3.12 lakh borewells, besides unreported sinking of borewells.

As per the data available, recharge from various sources is estimated only at 3,290 hectare metre per year. The drawing of water at present is 12,450 hectare metre per year, which amounts to 378 per cent, or nearly four times more than the annual groundwater recharge.

“With people resorting to indiscriminate sinking of borewells to the depth of 300 metre and beyond (which is beyond prescribed limits), this had led to illegal mining of groundwater. At this rate, the City’s aquifer will go dry and at least 24 lakh people will face water crisis,” he said.

There must be strict enforcement of the Karnataka Groundwater (Protection and control of drinking water sources) Act, 2003; The Bangalore Water Supply and Sewerage (Amendment) Act, 2009 and the Karnataka Groundwater ( Regulation and Control of Development and Management) Act 2011, to check the illegal mining of groundwater, he added.