As communities dig borewells hundreds of feet deep in the desperate search for water, the idea of simply digging a traditional open well may not cross anyone’s minds. That water can still exist at such shallow levels in Bengaluru, is unimaginable. But this is what Adarsh Palm Retreat (APR), a gated community in Bellandur, tried: Over the past year, the community dug three open wells, and are now able to use 25,000 litres of water daily from two of the wells.
APR is a 800-villa community spread across 128 acres; 550 of the 800 villas are currently occupied. The community suffered from a range of problems – water scarcity, also waterlogging, and seepage into the basements of villas. Residents consulted the design firm Biome Environmental Solutions on these issues.
Biome team, along with the research organisation ACWADAM, identified a shallow aquifer at depth of 10 m beneath the layout. Shallow aquifers are rock layers at shallow levels, that carry water. These aquifers quickly fill up during rains, and are usually unconfined, i.e, water in them move about relatively freely. Seepage into the APR basements was in fact caused by this shallow aquifer.
There were two more aquifers beneath the layout – one at intermediate level and another much deeper. The layout’s existing borewell was tapping into the intermediate aquifer, which was also unconfined. This meant that if any other borewell outside the layout tapped into the same aquifer, its water would drain there and the APR borewell would dry up making this borewell a very unreliable source.
On the other hand, the shallow aquifer that was identified, had the capacity to store three lakh kilolitres of water, i.e., 600 mm rain. “Biome team suggested that we could use the aquifer as a storage tank; it was a brilliant idea,” says Krishnaraj Rao, formerly RWA President and member of the RWA’s Water Management Committee. This meant that the community could draw water from the aquifer, but also had to fill it up during rains so that the aquifer never dries up. That is, both withdrawal wells and recharge wells had to be dug in the layout.
Biome team’s initial estimate was that 13 withdrawal wells and 635 recharge wells needed to be dug here in phases, over the years. The recharge wells would be designed as to capture 80% of the rain. This meant that the aquifer would be half-full – storing about 310 mm – during January to June, and would overflow during the more rainy months from July to December. The community could withdraw smaller amounts of water in the first half of the year, and consume comfortably in the latter half. Routing rainwater down to the aquifer would also solve the layout’s flooding problem. And the basement seepage problem would be solved as water gets drawn from withdrawal wells.
More importantly, shifting from borewells to open wells ensures sustainability. Borewells tap into deep aquifers that get depleted quickly and are difficult to replenish. But open wells tap into shallow aquifers that fill up quickly during rains. Open wells in Bengaluru have mostly dried up due to increase in paved surfaces and popularity of borewells. But if shallow aquifers are replenished, as in the case of APR, open wells can become a cheaper, long-lasting water source.
Last June, APR community dug its first open well. Water was struck at depth of five feet, and the well was dug till depth of 25 feet. But the water quality was poor since it had been stagnant for long and had mixed with sewage, says Krishnaraj. “So for 4-5 months, we merely pumped out and disposed the water. When we tested water quality after this, it was good,” he says. Water from the first and second wells are sent to the layout’s WTP (Water Treatment Plant), and used. At APR, water from any source is purified at the WTP before use. Water quality of the third well is poor as of now, but is expected to improve as in the case of the first well. The cost of digging these 5’X25’ open wells is Rs 60,000 each. Work takes couple of weeks.
Fifty two recharge wells have also been dug. Digging a 3’X20’ recharge well costs Rs 32,000; five such wells can be built in a week. “It is a work in progress. More wells will be dug based on the results from the existing wells,” says Krishnaraj.
He says that though residents have been supportive overall, there have been challenges, mainly with respect to finding locations for digging recharge wells. The ideal locations are the common areas in front of villas, but many villa owners object. Krishnaraj says this is because of lack of information. “Not everyone reads our emails, or attends general body meetings where the plans are discussed. When we approach owners about digging recharge wells, they are worried about aesthetics and that their plot will get flooded because of these wells. So we have had to educate and convince people one by one,” he says. The top slabs of the recharge wells are also painted green so that they blend in with the surrounding grass.
Reducing the community’s water demand is another challenge. Though the wells yield 25,000 litres daily, it still meets only around 3% of the community’s total water demand of 7-8 lakh litres per day. Once the empty villas are occupied, demand will increase further. As per Biome’s analysis, the water demand of residents was found to be unsustainable, at 233 lpcd (litres per capita per day). Biome recommended that the demand should be reduced to 135 lpcd for the community to be sustainable even for current occupancy.
Krishnaraj says that water demand had been reduced over the past three years by plugging leaks, installing water aerators, educating residents etc. Despite this, demand remains high at over 220 lpcd. “We still do ask residents to reduce usage. There was also a proposal to install meters to reduce consumption, but it is on hold currently,” says Krishnaraj.
He says that, gradually, as more wells are dug, more water could be drawn from the aquifer to meet more of the community’s needs. There are plans to dig five more withdrawal wells now. “We are a huge community, and our water demand is very high. Smaller communities may be able to fully meet their water needs through a project like this,” he says.
APR’s example shows how identifying and understanding our aquifers – rather than indiscriminately drilling borewells – would provide efficient solutions to our water needs. It also demonstrates how communities can tap into the potential of shallow aquifers, and replenish these only using the rain falling in their premises.