Harvesting every raindrop helps Bengaluru survive monsoon

Copious rains in recent weeks have yet again exposed the city’s weak monsoon preparedness

Rain Water Harvesting

Rain Water Harvesting

Flash floods, waterlogged roads, inundated homes… The rains have unleashed their predictable annual misery dose yet again. But as the city’s grossly underequipped system struggles as usual, a faint hope lingers: Can this excess water be harvested to quench next summer’s thirst?

One look at Bengaluru’s Rainwater Harvesting (RWH) record, and you know the hope cannot be grounded in reality. Despite stringent rules in place, only an estimated 1.26 lakh buildings have installed RWH systems, mostly in the peripheral areas. The rules are clear: The amended Bangalore Water Supply and Sewerage Board (BWSSB) Act 2009 mandates RWH systems for all buildings built since 2009 on sites measuring 1,200ft and above, and for all buildings constructed even before 2009 on sites of 2,400ft and above.

Patchy enforcement

But adherence to rules and enforcement have been patchy at best. Lack of regular inspection has meant the guidelines are diluted, and harvesting is superficial. However, one silver-lining has been the record of outlying areas, where perennial water shortage is forcing people to turn to RWH as a real, workable solution.

“We are doing reasonably well in RWH, particularly on the outskirts. In the peripheral areas, borewell recharges too have picked up. However, BWSSB should stop charging people who use recharged well water. This is a disincentive, it needs to be corrected at the policy level,” notes S Vishwanath, director of Biome Environmental Solutions.

Recharge wells

Under a unique ‘Million Wells’ movement in 2018, Biome, Friends of Lakes and India Cares Foundation had dug over 1.2 lakh recharge wells, employing rainwater as the resource. Most of these were in the city’s water-starved areas on the periphery. Beyond homes, RWH has been adopted in many institutions, both government and private. But in the open public spaces, a concoction of poorly designed drainage systems, sewage-filled storm water drains (SWDs) and encroachments of lakes and lakebeds has made a mockery of harvesting.

Ninety-five per cent of the city’s sewer lines run on gravity, notes Thippeswamy, former BWSSB Engineer-in-Chief. “Surplus rain water gets into the SWDs that are filled with sewage. They are doing a hotchpotch job of remodelling and rehabilitating the drains. BBMP, being the custodian of the SWDs has no iota of thinking on rain water reuse,” he points out.

Eleventh hour drain desilting works have predictably failed to arrest urban floods. Is there an out-of-the-box fix to conserve this excess water? Why not, for instance, build large underground reservoirs in low-lying areas to collect water that otherwise floods houses and triggers big misery?

Underground reservoirs

Many institutions with large campuses have built wells and artificial ponds / lakes at the lowest points, notes Thippeswamy. “This is possible in public spaces too, as demonstrated in many European cities that face flooding risks. Such reservoirs with a water treatment facility nearby can prove effective.”

But to ideate, fund, build and operationalise such innovative solutions, civic agencies working at cross purposes will not do. “Entire water management of the city should be under one board. Look at how efficiently Singapore manages with its Public Utility Board, coordinating water management, groundwater, lake development and more. The government should realise that water is most important for the economic development of any city.”

Rainbow Layout experience

Perhaps the agencies could learn a few strategies from the residents of the 20-year-old Rainbow Drive Layout on Sarjapur Road. Ex-president of the Plot Owners Association, K P Singh recalls how the residents thought well ahead into the future, foresaw the water crisis and adopted RWH as a robust solution.

Harvesting the annual rains has worked fantastically well for the 285 houses that are part of this 35-acre colony.

“Since the colony was far away from the city centre, we realised there was no way we would get Cauvery water. Our way out was RWH, making it mandatory for every house to dig 25ft deep recharge wells,” Singh recalls.

The mandatory rule worked so well that the layout’s two borewells deliver 3 lakh litres every day, twice the daily requirement of 1.40 lakh litres. “These borewells, both less than 130ft deep, have been catering to our water needs for the last 20 years.”

The recharge wells were placed at three levels, inside houses, on road sides near storm water drains and inside the parks (40ft deep). “We are now self-sufficient in drinking water. The water quality is so good that we don’t need any filtering!”