The South West monsoon has come calling. Are you doing your bit to harvest rainwater?

The skies are overcast most days. The evenings see a steady drizzle and the occasional downpour. Most of the water runs down streets and flows into drainage canals, or gathers in puddles and evaporates soon after.

This would not happen if every building and street had in place functioning rainwater harvesting (RWH) structures, say experts. Functioning, because most buildings have structures constructed to comply with Government rules. Few have been maintained.

Silt, rubble, plastic and trash choke the pits where rainwater harvested from rooftops flows into. But, there are happy stories that prove that if maintained well, RWH structures effectively recharge the groundwater table, says K. Mylswami, project co-ordinator, Siruthuli, which has helped put up many such structures across the city.

“The system is already there, you just have to rejuvenate it. That will cost you a day’s labour and less than Rs. 1,000,” he says, ruing that 75 per cent of people do not maintain these pits.

If you have a pit that has not been maintained, act now, because the South West monsoon will last till September.

Suchi Dalmia, who lives in R.S. Puram, still remembers the brutal summer of 2012. “We struggled to store water and the borewells ran dry. This year, we decided to put in place a proper RWH system before the monsoon. We got it done at home, and in our factory and farm. At home, it’s a very basic system, and we’ve planted colourful flowering shrubs around it. At the farm, we went in for staggered trenches so that the water does not run off into open ground. The system was put in place in February-March. The yield from our coconut trees is already better.”

PSG College of Arts and Science has 11 RWH structures with borewells. K. Natarajan, administration officer, says the pits are regularly cleaned. “The pits adjoining the tar-topped roads don’t gather much silt. But, the others need to be cleaned at least once in three months so that they are in a constant state of readiness to receive rainwater.”

The RWH systems inside the central jail are also active. Five huge pits draw in the water that washes down the 175-acre premises.

Siruthuli says failed borewells can be revived by constructing recharge structures around them. Water collected this way directly recharges the aquifers. At some stage, the borewells will spout water. “We have worked on many failed borewells in Coimbatore and outside,” says Mylswami. Suchi has in place such a system too. “I hope we can use our borewell one day again,” she says.

While the success rate in individual buildings is low, RWH systems work well in gated communities. Parsn Sesh Nestle, Nanjundapuram, has an efficient system. So do Sreevatsa Enclave and Sreevatsa Gardens on Mettupalayam Road, among others.

RWH compliance

The Coimbatore Corporation has stepped up efforts to ensure RWH compliance. “Whenever anyone applies for plan approval or a water connection, our staff assess if the building has an RWH structure. Only then is approval given,” says K. Sukumar, Executive Engineer, Coimbatore Corporation.

Most Government buildings have a working RWH system in place. “We even have roadside structures to tap the excess run-off,” says Sukumar. As for maintenance, “from now, staff visiting homes to read and record water meters will check if the RWH structure is functional”, he says.

Desilt RWH pits

Collection of silt and debris in the pit is the only major problem an RWH structure faces. To set this right, workers remove the filter material, clean it of silt and refill in into the pit. This will ensure speedy percolation. This system is cost effective and does not require trained labour.