Bengaluru's only hope: Revive the 1,000 lakes Kempegowda built, stop depending on Cauvery

Half of Karnataka’s share of the Cauvery is impounded for Bengaluru. The city’s water utility spends 60% of its budget pumping water uphill. The city wastes much of it pumped up. And where are Kempego
NAgesh polali
NAgesh polali

BENGALURU: When summer delirium gets real high, Bengaluru remembers the 1,000 lakes Kempegowda built. Only about 100 of them remain, some of them on paper and the rest in various stages of evaporation. Experts have been saying for years that if Bengaluru has to wean itself away from the Cauvery, a revival of the lost lakes is necessary.

With the perennial drought taking storage levels in the Cauvery basin to the lowest recorded in recent times, researchers, hydrologists and environmentalists recommend three urgent measures: harvesting of rainwater, revival of lakes and recycling of sewage water. This will contribute 30 tmc ft of water annually, thereby mitigating the dependence on the spent Cauvery.

Burden on Cauvery
Traversing a distance of 120 km, the river Cauvery remains a major source of water for the ever-growing city. In fact,Bengaluru consumes about half of Karnataka’s allocation of the river’s water, leaving other cities deprived. But what is shocking is that of the 1,450 million litres of water pumped into the city every day, 600 MLD goes waste due to distribution loss and illegal connections. This is the second highest for any metro after Kolkata.

Currently, the city’s annual requirement of water is 20 tmc ft, which is met mostly by the Cauvery. Added to this, Bengaluru Water Supply and Sewerage Board (BWSSB) spends a whopping 60 per cent of its budget to bring the river water to the city, which is at a height of 540-800 m above sea level. In the process, the city’s own water resources, its chain of lakes and tanks, including the Thippagondanahalli reservoir, have been forgotten for over three decades.

Scientific Study
Studies carried out by scientists and urban planners lay out a clear roadmap for reducing Bengaluru’s dependence on the Cauvery water.

A recent study by Indian Institute of Science, Bengaluru, suggests that if the city’s 123 remaining lakes are revived and rejuvenated, nearly 30 tmc ft of water can be generated annually. Dr T V Ramachandra, coordinator of the Energy and Wetlands Research Group (CES) of IISc, and other researchers conducted a study on 105 lakes and published a report ‘Water Situation in Bengaluru’ in 2016, suggesting ways by which the city can meet its water needs.

But this requires decisive government and public action. The report says, “If all the silt and slush in these lakes are removed, and the water body is rejuvenated and protected, they are capable of holding 30 tmc ft of water. However, waste water has to be treated scientifically by constructing wetlands and algal ponds. Currently, it just passes through sewage treatment plants that do not remove the contaminants completely.”

In its report, the Wetland Group outlines, “The city receives an average annual rainfall of 750-850 mm, and if harvested and stored in lakes, it will generate 15 tmc ft of water while another 5 tmc ft can be generated from recycling sewage. In fact, if the entire sewage water is recycled, it will generate 16 tmc ft annually.”

Linkages, inter-connections
Water experts also stress that linkage of storm water drains to lakes should be set right. Eshwarappa Madivali of People’s Campaign for Right to Water, Karnataka, points out, “With natural flow of water on an undulating terrain, rainwater should be allowed to flow from the hills to the three valley systems that exist in the city by clearing and recovering storm water drains.

This will lead to storage and recharge.” Urban expert Ashwin Mahesh goes a step further in his report ‘Mathondu Cauvery’, submitted to the govt last year, stating how lakes can be efficiently utilised. He says that watersheds have to be vastly improved for better collection of water. “This will ensure harvesting and collection of water over a large area of 750 sq km under the BBMP.”

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