Over the decades, as the population of Bengaluru has increased and now touched nearly 1 crore, the Cauvery has remained the primary source for drinking water in the city. The city’s dependency on the Cauvery will furthermore increase by 2021, when the projected population will touch 1.05 crore. According to experts, Bengaluru will require an additional 8.19 tmcft of water annually by then.
The river water is being pumped in four stages — over 1.5 tmcft a month — to supply to core areas where a piped network has been established. In the outer-lying areas, which now includes plush apartments and IT complexes, and represent some of the fastest growing localities in the city — residents rely on borewells and tankers for water. A fifth stage of water supply from the Cauvery is being envisioned to supply to these parts.
The city’s erstwhile water resources have dried up in the past few decades as urbanisation took hold of the region. As Arkavati, a non-perennial river, dried out, water levels in the Hessarghatta and T.G. Halli reservoirs plummeted. Similarly, groundwater has dropped as more borewells (more than 3.15 borewell enumerated in 2011) are drilled.
An experts’ committee set up in 2011 by the State government to come out with recommendations on quenching Bengaluru’s thirst suggested in its report diversion of 30 tmcft of water from the Sharavati (Linganamakki reservoir), as an alternative to the Cauvery waters.
The committee’s chairperson Thyagaraj, former BWSSB chief engineer, said this diversion would not involve any inter-State dispute. Moreover, it would not affect farmers as water from this reservoir is not used for irrigation downstream, he said.
Another alternative would be diversion of water from the Barapole river that originates in Kodagu and flows through Kerala to join the Arabian Sea, he said.
But are these engineered alternatives feasible, considering that the alternative reservoir (Linganamakki) suggested is about 350 km from Bengaluru, surrounded by eco-sensitive Western Ghats range? It will involve pumping over great distances and heights.
Captain Raja Rao, former irrigation expert, said the first priority should be to check unaccounted for water and stop water leakage.
“We cannot sacrifice power generation in Linganamakki to divert water for drinking,” he said, and added that an evergreen best alternative would be to harvest rainwater.
A.R. Shivakumar, principal investigator for RWH at the Karnataka State Council for Science and Technology, Indian Institute of Science, said if every household harvested rainwater, Bengaluru’s water woes would drop dramatically. Bengaluru’s annual rainfall had a potential of meeting nearly 50 per cent of the city’s annual Cauvery water allocation of 19 tmcft, he said.
“The city has around 60 rainy days in a year and receives an average annual rainfall of 972 mm. This means the city has a potential of getting 23 tmcft of rainwater. But, with most of the lakes having dried up or filled with sewage, the rainwater literally goes down the drain,” he said.
City’s erstwhile water resources dried up in the past few decades as urbanisation took hold of the region
