In the arid “wild west” of the city, where explosive growth has seen residents dig deep for water, it is open wells that could provide the solution to water problems.
Around Sarjapur Road, where, despite the lack of piped water supply, nearly 30 open wells continue to provide water while borewells are seeing a high rate of failure. These were the findings of a three-year-long study to map the aquifer (groundwater) in the Yemlur watershed.
The area is home to several residential apartments and towering IT complexes.
The study conducted by Biome Environmental Trust, Advanced Centre for Water Resources Development and Management (ACWADAM) and Wipro took up Yemlur watershed — which spans 33 sq km — covering Bellandur, Marathahalli, among other areas witnessing rapid growth.
The estimated water demand was more than 100 million litres a day (MLD), and much of the pressure falls on groundwater. Perhaps, this is reflected in the analysis of the State’s Groundwater Directorate, which shows that areas in and around Sarjapur have seen the worst dips in groundwater table — where the average depth of borewell dug was over 1,200 ft.
The study sought to tap into groundwater users to understand the drawing of water as well as the aquifer present. One of the surprising findings was to dispel the myth that deeper the borewell goes, more the water.
“The high-functioning borewells that give up to 1.5 lakh litres a day is within 600 ft underground while availability of water is limited beyond this depth. Instead of digging deeper, it makes sense to have more recharge structures,” says Shubha Ramachandran of Biome. However, open wells were found to have water even at depths of 60 ft, and provide better quality of water. The study also found that open wells benefit from rejuvenated lakes while borewells largely seem unaffected. After the rejuvenation of Kaikondrahalli lake, nearby open wells sprang back to life — four of them now give 50,000 litres a day. At Kasavanahalli, a single open well gives 40,000 litres of water a day. Their analysis showed that during monsoons, the lakes recharged open wells, while during dry seasons, water seeped from open wells into lakes.
Like the deep aquifer, the shallow aquifer too have remained largely dry in the watershed — a result of neglect of recharge pits and high concretisation leading to rainwater run-off.
However, there is hope, shows the study, with numerous communities leading the way in recharging the aquifer. Peddanna, a well-digger from Anekal, says that since 2008, at least 3,000 recharge wells have been dug in the region. “The demand keeps increasing as more people realise its importance,” he says.
Published - August 12, 2017 09:14 am IST
