Can Bengaluru ever get a ‘drinking water’ lake?

As the city heads for another summer spike in water demand, lakes fed by last year’s record rains tell a different story beneath their surface

Rasheed Kappan | NT

Bengaluru: Last year’s record, unprecedented rains seemed to bless Bengaluru with better lakes than ever. But look beyond the surface, and you see only muck. Not de-silted in time to boost their water-holding capacity, the lakes look nowhere close to being a drinking water source as another summer demand prepares for a scorching spike. It beats common sense.

Thousands endured flash floods and hopelessly inundated low-lying areas as the record-breaking downpour played havoc in many parts of the city. They hoped such massive volumes of rainwater would flow into lakes and sink in to recharge the groundwater, offering muchneeded relief from the recurring annual summer crisis.

But barring a few lakes in the preliminary stages of de-silting, the bulk of Bengaluru’s 193 surviving lakes have their water-holding capacity drastically reduced. Reason: Decades of unregulated inflow of sewage through heavily polluted and encroached stormwater drains (Rajakaluve).

The much-delayed drain-remodeling exercise could have offered a respite, but shows no signs of completion. The intensity of the rains was so severe that rainwater should have percolated through the sewage.

“But once it percolates, what is the quality of water that you get in the borewells is another question. Does it meet the Central Pollution Control Board (CPCB) standards of phosphate and nitrate content?” wonders V Ramprasad, environmentalist and co-founder, Friends of Lakes (FoL).

Contaminated infiltration

The warning signs are dire: “We may end up with high amounts of phosphate, huge amounts of algae and bacterium in the lakes. It will settle at the bottom and after some time, start bubbling out methane gas. One fine day, you will complain that the lake is catching fire. One hundred percent, it will catch fire,” he says.

Rejuvenating lakes to eventually serve as sources of drinking water mandates that only clean rainwater gets in and is maintained that way through robust rainwater harvesting. The city’s water bodies were originally designed for precisely that purpose, as reservoirs that could also mitigate floods.

Why compromise?

But, as Ramprasad points out, there is a resignation that Bengaluru will never see a drinking water lake.“Why should we make that compromise? Does this mean that drinking water should only come from outside so that we will always remain slaves?” he asks. There seems to be no political will to free the city from its total dependency on the outside (read Cauvery) water.

“Politicians want that reliance to stay strong. That way, they want to control the prices, assuring voters that they would give them free water. Being very important, water is becoming a political tool for vote banks.”

Concretisation

Barring a few lakes that were de-silted, large swathes of Bengaluru have not seen a perceptible improvement in groundwater recharge for one big reason: Concretisation as Dr T V Ramachandra from the Indian Institute of Science (IISc) Centre for Ecological Sciences informs, “Eighty-five per cent of Bengaluru’s landscape is choked with concrete.” Studies anchored by IISc and Dr Ramachandra have shown that vegetation helps the infiltration of 45 to 60 per cent of rainfall into the groundwater.

“That is the water we get post-monsoon. Wherever infiltration has not happened due to concretisation, you will see scarcity of water. Over the last 50 years, vegetation cover has come down to 4 per cent of Bengaluru’s landscape.

Combine this with a 79 percent loss in water bodies. People are also dumping construction and demolition waste into the rajakaluves. That is why water is not flowing to the lakes,” he explains. Ecologically sound lake rejuvenation can work. Sarakki lake proved it, so have the Bellandur and Varthur lakes now going through the de-silting process.

“In Sarakki, within a year of the rejuvenation, we saw an increase of 320ft in the groundwater table. It clearly shows that open spaces, lakes and greenery will help in groundwater recharge.”

No de-silting, no reservoir

Cosmetic lake upgrades, the rule rather than the exception, has meant the original reservoir concept has been ignored. As Ramprasad points out, “None of them are de-silted to the original water-holding capacity as per the law. About a metre or a maximum of 1.5 metres is what they do. That doesn’t mean anything.”

For years, the standard practice to quench the thirst of areas added to th