HYDERABAD: Forget the rainwater harvesting pits. Its time to create and concentrate on groundwater recharging shafts. As the West Zone of the city remains parched with no legal water connections in place and several illegal borewells dried up, groundwater experts are suggesting that its time to move on from the traditional rainwater harvesting pits.
According to experts, these pits, which were built in and around the north-western part of the GHMC limits, are too shallow to recharge the parched rocky terrain.
As per the latest groundwater report prepared by the State government’s Ground Water Department, Rangareddy, Medak and Medchal districts saw a sharp fall in the groundwater levels between 2018 and April, 2019. The rate of fall in these districts were 3.87 meters, 4.22 m and 4.92 m respectively.
“These areas of the city have hard rocks and groundwater level has fallen very deep... upto 20 meters in some areas. These regions, which have a very high density of population, are also witnessing less rainfall and making groundwater levels drop dip faster than the time it takes to recharge,” noted Dr Pandith Madhunure, Director of Ground Water Department.
Dr Pandith opines that in such a scenario, building simple rainwater harvesting pits of five to six feet depth will not help bring up the groundwater levels in the rocky terrains of north west Hyderabad.
For areas like these, the TS Ground Water Department has now taken up the work of building specialised rainwater harvesting shafts which are a combination of the rainwater harvesting (RWH) pits and slotted pipes that can recharge the water up to the weathered zones in the deep rocks. The work at present is being taken up in remote villages with high distress.
In this method, a 3x3 feet RWH pit is created around the borewell and the borewell case is equipped with slotted pipes which run deep and take water to parts of the inner earth where there are ‘weathered’ zones or fractures in rock and replenish it.
“For areas stretching from West Marredpally to Kukatpally, Ameerpet to Serilingampally and all the way to Shaikpet, wherever the groundwater levels are critically low and there are dried up borewells one could go for the rainwater harvesting shafts,” Dr Pandith said.
As per officials, transforming a borewell into a rainwater harvesting shaft requires an additional 3x3 feet space to capture the runoff rainwater and some slotted pipework. A shaft built from scratch can cost up to Rs 1.7 lakh, they said.
At present the said methodology has been implemented across 140 odd areas, however, it has been undertaken in the remote districts with acute distress. The department is also in the process of floating tenders for 400 more such structures in districts that are severely impacted.
“In the Hyderabad city, we are encouraging people to come to us for technical guidance. With this method, a house can get up to 35 to 40 per cent of its water needs,” added Pandith. The Rainwater Department of HMWSSB is also suggesting a similar method of making additional injection wells strategically beside borewells to replenish them.
Meanwhile, Prof K Purushotham Reddy, a city-based environmentalist, described it as a feasible method.“This recharging of groundwater shafts is doable under laboratory conditions as the condition is rocky in the subsoil. However, the authorities must be answerable on why the conventional rainwater harvesting methods were not implemented. If implemented properly, those methods would have helped in avoiding the groundwater levels falling further,” he said.