Urbanisation Seen As Threat to Water Table
VIJAYAWADA: Do you know, by constructing a single bedroom house, you are obstructing 50,000 litres of rainwater from percolating into the earth and recharging the groundwater levels?
Experts say, if the average annual rainfall (103 cm) in Krishna district is taken as a base, the average rainfall collected on a two-bedroom house constructed on 60x40 feet house plot will be 1 lakh litres.
Nowadays, the houses, especially those in urban areas, are being constructed in such a manner that there is no scope for the rainwater to percolate down, as the entire area is covered with cement and even the space between the road and the compound wall of the house is covered with materials that will not allow the rainwater to percolate. Hence, the rainwater flows down the road, often resulting in complaints of overflowing drains, and gets wasted as most of it evaporates in time.
Increasing urbanisation, expected to take place in the coming years, will only decrease recharging of ground water levels if care is not taken to ensure to let the rainwater collected on the rooftops percolate into the ground. “We can compensate it simply by constructing rainwater recharge pit. If every individual does it, the collective effort can boost the ground water,” says groundwater department deputy director A Varaprasada Rao.
All it requires is to have a 2x2x1 m (i.e., 4 cubic m) of pit dug out and refilled with boulders, gravel and coarse sand in layers. The topmost layer should be filled with either jute mats or coconut coir to prevent sedimentation of finer particles above. Such pit can be covered with gully grates made of cement or iron.
“The 4 cu m pit will have a capacity to contain 4,000 litres of water, but once it is refilled, it retains 40 per cent of void space i.e., 1,600 litres. By constructing such rainwater recharge pits, some amount of water can be allowed to percolate,” he explains.
Experts advise the revival of old tradition of farm ponds in agriculture, which help not only recharge the groundwater levels but also retain the moisture levels in soil.
In the past, a pond was used to be constructed in 1 per cent of the total land i.e., one cent per acre of land. If it is only one acre land, the farm pond will come up in 48 sq yards and will have 50 cu m of capacity i.e., 50,000 litres.