BENGALURU: As an emergency measure in case of a water shortage in the city, the water in the Thippagondanahalli (TG Halli) reservoir can be used after it is treated extensively. And if the heavy rains continue for another few days, it could even provide water which doesn’t need treatment.
Located 45 km from the city, this reservoir on Magadi Road used to play a crucial role in catering to the drinking water needs of North and West Bengaluru 15 years ago. Water from catchment areas of Kumudavathi, Hesaraghatta and Arkavathi rivers used to fill up the reservoir.
With a height of 74 feet, the dam that was built in 1933 can stock up to 3.5 TMC (thousand million cubic) feet of water. “The maximum water TG Halli was capable of providing the city when filled up to the brim was 135 Million Litres Per Day (MLD),” says V Mahesh, Chief Engineer (Cauvery), Bangalore Water Supply and Sewerage Board (BWSSB).
Areas that benefited in the North included Vijayanagar, West of Chord Road, Banaswadi, Nagpura and Rajajinagar and the West were Gutahalli, HMT Layout, Yeshwantpur, Mathikere and Malleswaram.
The reservoir’s maximum capacity was reached in 1998 but since then, water storage levels have dipped due to poor rainfall. It later reached a stage when the reservoir could supply the city only between 20 and 30 MLD, he added. Bengaluru’s daily water requirement today is 1,400 MLD. This and the contamination of water gradually made the water unfit for consumption and by November 2012, water from here was not drawn to the city, Mahesh said.
The Total Dissolved Solid (TDS) level, a measure of water quality, stood at 930 mg/litre as of September 6, he said. The maximum permissible TDS level is 500 mg/litre. Even the high level of TDS can be specially treated and water supplied to North and West Bengaluru for 1.5 months in case of any emergency, said S Krishnappa, Engineer-in-Chief, BWSSB. Only if the Total Organic Carbon level is high does the water become unusable, he added.
There is a catch though. “Reverse Osmosis required to treat this water would be very costly,” said Rama Gowda, Executive Engineer in-charge of TG Halli. The reservoir presently has water up to 31 feet. “If there is copious rain and it touches up to 40 feet, then the TDS gets dissolved due to the fresh water supply,” he said. In such a scenario, water can be supplied directly through pipelines without even treating, he added. Pipelines have been laid only to North and West Bengaluru.