May 18: With drinking water being scarce the government is right in hunting for sources from where more of it can be supplied to the city. But its latest solution — to create six artificial lakes using rain water — seems more of a pipedream, going by experts in water conservation.

While on the face of it there seems little wrong with BWSSB minister, Katta Subramanya Naidu’s argument that Bengaluru should make use of the 800 mm of rain it receives annually to increase the city’s water supply by 22 TMC, instead of letting it go waste as is being done today, the logistics involved make the whole idea seem impractical.

If the government goes ahead with its plan, not only will the water board need to acquire around 1,370 acres of land around the city to create the six lakes at a cost of Rs 4,500 crore, but it will also have to make sure that storm water drains that run through the entire city are free of sewage, so that at least 35 per cent of the rain water is collected to supply Bengaluru with 10 TMC of water over the next few decades.

Water conservation experts point out that making storm water drains sewage-free is almost an impossible task as it will require a complete overhauling of the old and corroded underground sewerage network of the city and making sure that all homes have a sewerage connection so that they are not tempted to let their sewage into the storm water drains.

So while in principle the idea of creating the six lakes is laudable, is it really feasible, they ask, also wondering why the government even needs to create these lakes, when there are so many that can be revived if only sewage is not let into them.

According to a study conducted between April 2009 and March 2010 by the Lake Development Authority (LDA), except for 12 lakes all the others in the city are sewage-fed and polluted. “Many of these lakes too are man made.

They were once seasonal, but now have become perennial as they are constantly fed with untreated sewage,” says U.V. Singh of the LDA.

Treating the water of these lakes, contaminated with heavy metals like zinc, lead, iron, nickel, and cadmium, and with nitrates, sulphides, phosphates, carbonates and coliforms, will require huge investment in technology to carry out processes like hydrolysis, electrolysis, and reverse osmosis and even then their water cannot be used for drinking, say the experts, warning that if the government creates more lakes it will be only adding to the number of contaminated water bodies dotting the city and its outskirts.

S. Vishwanath, a water management expert and advisor, Arghyam, feels a better solution, would be to recharge the ground water through rainwater harvesting and invest in reviving the city’s existing water sources like Thippagondanahalli, Hessarghatta and Arkavathi.

Another suggestion is that BWSSB should let treated sewage into lakes to keep them perennial and then sink borewells around them to draw water, which will be safe even for drinking.