WATER WISE
Open your eyes to the reality of water crisis
S. VISHWANATH
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A clean roof, a rainwater sump and a recharge well…it takes all these and of course your determination to get the shower harvested in your layout for a lifetime.
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A recent news item said that the Bangalore Water Supply and Sewerage Board (BWSSB), the sole provider of piped water in the city of Bangalore, had temporarily stopped giving new water connections to even individual homes.
The reason stated is the simple non-availability of enough water especially from Thippagondanahalli reservoir on the Arkavathy.
This is time for the city to wake up and look at the reality of the water crisis facing it and to participate in the solution. Rainwater harvesting provides this opportunity.
The layout plan
New layouts are coming up all across the periphery of the city. There is also a steep decline in groundwater availability in the periphery as borewells are the major source of water. The layouts can very easily plan for rainwater harvesting. Here are the details.
Every vacant site should have its own water harvesting structure — raised earthen bund of a foot all around and a recharge pit in the centre.
After construction commences, each house should have its own arrangement for water harvesting. Rooftop rainwater should be filtered and stored in a small sump for use.
Recharge well
Excess water should be allowed into a recharge well. This recharge well should be planned in the storm water drain network and should be usually 2 to 3 feet in diameter and about 10 to 20 feet deep depending on the percolation rate at the site.
The recharge well can very easily be located in the storm drain itself or slightly off it.
Storm water run-off from the roads should also be led into these recharge wells. The overall objective being not to allow a drop of rainwater to go out of the site, but to be used to augment groundwater.
The shallow aquifer in most parts of Bangalore have the capacity to hold a significant amount of water. They also permit the recharge into deeper parts of the ground and into the secondary porosities from where borewells draw water.
By recharging the shallow aquifer through recharge wells, layouts can augment groundwater and ensure a longer life for their borewells.
Catchment management strategy
Since after the construction of roads and buildings on a layout the impervious layer increases, most rainwater runs off from the layout.
It is, therefore, necessary to help the percolation of water into the soil and keep the water in. A good clean catchment is a must.
No garbage should be allowed to accumulate anywhere on site and segregated garbage should be positively managed.
No chemical contamination through oil and petrol spills should be allowed and sewage should be adequately treated. Such a catchment will facilitate good, clean rainwater run off.
For an individual home or an apartment, the roof is the catchment area. This must be kept clean. No junk should be stored here. Rainwater falling on such a clean surface will be of very good quality.
This rainwater should be filtered and stored in a sump tank. The overflow should be left into a recharge well.
Overall impact
An acre of layout with 900 mm of rainfall gets nearly 36 lakh litres of water falling on it. It is possible to harvest 80 per cent of it through careful planning, that is nearly 29 lakh litres.
This rainwater management will involve a clean roof for every house, a storage sump of 6,000 litres and a recharge well. If every layout makes rainwater harvesting happen, then Bangalore can tackle its water shortage.
If we do not harvest rain, we face a water shortage of calamitous proportions. The choice is ours.
(The author can be contacted at 23641690 or zenrainman@gmail.com)
Go into www.rainwaterclub.org
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