JOIN USRight time to harvest rainwater, say experts
With the south-west monsoons active in Bengaluru and the north-east monsoons just around the corner, now is the right time to start rainwater harvesting, say experts.
While the south-west monsoon usually ends by September-end, the north-east monsoon lasts from October to December. According to the Meteorological Centre of Bengaluru, the city has about 40 more rainy days left this year.
“Bengaluru is set to receive over 200 mm of rainfall in September, 140 mm in October and 40 to 45 mm in November. That is effectively 40% of the city’s rainfall in the next 80 to 90 days,” says Ganesh Shanbhag, software engineer and water conservation evangelist. Since 2019, he has helped about 150 apartment complexes set up rainwater harvesting (RWH) systems.
“If you set up an RWH system today, you can still harvest about 30% of the city’s annual rains. This will not only have financial benefits but you will no longer have to worry about water shortage in your household,” he says. Water conservation expert Vishwanath S echoes the opinion. “Now is a good time to start rainwater harvesting as one can collect rainwater quickly and use it productively,” he says.
In the last few years, the city has received bountiful rainfall but residents are still complaining about water shortage. “Setting up a RWH system will definitely help reduce this problem,” says Vivek Chandra, owner of a rainwater harvesting company near RR Nagar. About 45 minutes of rain can provide about two lakh litres of water.
Reduce flooding
Torrential rains in Bengaluru have once again brought to light flaws in the city’s infrastructure, leaving roads and homes flooded. Rainwater harvesting can help solve this problem, at least partially, says John Daniel, whose company provides rainwater harvesting solutions. “If the rainwater is harvested it won’t come into the house or even flood the roads,” he says.
Typically water flows in from a high area and floods low-lying areas. “If high areas can hold rainwater and recharge the groundwater, they can reduce flooding,” explains Vishwanath.
There is a high interest in reviving old open wells during the rainy season, he says. “At many places where the wells are full, people are using the water,”
he adds.
Setting up rainwater harvesting on a large scale calls for the installation of a recharge or injection well. A team of trained well-diggers can do it in two days. “We’ve got more than two lakh recharge wells installed across Bengaluru,” he says. Ganesh’s apartment complex in Singasandra had a basement flooding problem. “Earlier we used to pump out the water to BWSSB water lines. But now we have diverted all the storm water into a defunct borewell. This acts as an injection well. Now water from this injection well can be used for several purposes in the apartment,” he says.
Along with rainwater harvesting, he says stormwater harvesting is important. A simple solution that can help save the city from imminent rains is to turn all defunct borewells into injection wells, he says. “Stormwater harvesting should be a priority right now. If all the flood water is redirected towards the borewells, it will in turn go and recharge the aquifer,” he says.
Bengaluru is currently running out of deep aquifers. “Every city has two levels of aquifers, shallow and deep. What is happening in Bengaluru is that while we have recharge wells, they are only recharging the shallow aquifer and the deep aquifer is not getting replenished,” he explains. If the deep aquifer is replenished, Bengaluru will no longer need to depend on sources outside the city for water, he says.
Won’t rain hinder RWH work?
The current rains are not a hindrance if you want to set up a rainwater harvesting system at your house or apartment, say experts. “Lately, the first half of the day has not seen rain. Plus, even if it rains, it may cause half a day’s delay,” says Vivek Chandra, owner of a rainwater harvesting company. An RWH system calls for water pipes, a filter and a storage tank.
“All buildings have the piping system already installed, and they just need to be fitted with a filtering system and a storage tank, which can be bought at any store. It is an easy and quick process. In fact, I know people who started harvesting rainwater during the course of this monsoon,” says water conservationist Ganesh Shanbhag.
Water language
Injection well: An injection well enables the flow of water deep underground into porous rock formations.
Recharge well: It is a groundwater recharge technique that directly discharges water into deep water-bearing zones.
Aquifer: An aquifer is a body of porous rock or sediment saturated with groundwater.
Rainwater harvesting: It refers to the process of collecting and storing rainwater, for future use.
Stormwater harvesting: It refers to the collection and storage of surface water resulting from heavy rains.