Recharged aquifers, only solution?

Summer prepares for yet another seasonal assault and the thirsty city could be caught napping again. Dried up borewells, parched groundwater table, costly tankers, the story is predictably repetitive on the outskirts. Can a pre-pandemic recharge initiative through shallow aquifers offer a sliver of hope this year?

Out there in the 110 villages linked to the Bruhath Bengaluru Mahanagara Palike (BBMP) in 2007, the network of Cauvery pipelines is only ready in parts. Yet, residents say the connection cost is so prohibitively expensive that they better stay with private tankers.

Also read: Ensure piped water supply, stress on harvesting

But how far can this reliance on tankers that source water from agricultural lands outside the city’s boundary last? In Mahadevapura, where the demand slips into crisis mode every year, tankers that ferried water from borewells in Varthur are now forced to scan wells in Hoskote and beyond, a recipe for heftier bills.

Shallow aquifers

So, are shallow aquifers the solution? Beyond borewells, tankers and even the Bangalore Water Supply and Sewerage Board (BWSSB) network, these aquifers were first spotted by chance in mid-2019. Inspecting the cause for water seepage into the basement of a villa in Devarabeesanahalli near Bellandur, residents stumbled upon this source with huge potential.

As Whitefield resident and civic activist Elangoven Kulandaivelu recalls, “They tried digging an open well close to the basement to trap the water outside. To their surprise, the water continued to remain there even as borewell water levels depleted.”

Also read: Recharge wells, a strategy explained

Digging more open wells within Adarsh Palm Retreat (APR), the gated community of about 800 villas spread over 128 acres, in due course, discovered a whole new alternative. Elangoven feels such shallow aquifers could be underneath in plenty across the areas once lush with agricultural fields.

These are rock layers at shallow levels, carrying water. They quickly fill up during rains, and the water moves about relatively freely. In APR’s case, it seeped into the basements. The shallow aquifer was soon estimated to hold three lakh kilolitres of water, equivalent to 600mm of rain.

Storage tanks

Design firm Biome Environmental Solutions suggested that the aquifer could be turned into a storage tank. The dynamics suddenly changed. The gated community could now take water from the aquifer but they had to ensure that rains filled it up so that it never goes dry. This meant digging withdrawal wells and recharge wells.

This switch from borewells to open wells made eminent sense. Borewells are designed to tap into the deep aquifers. But this depletes the aquifers quickly. Open wells, on the other hand, tap into shallow aquifers that fill up during rains.

This is no rocket science. But the ‘official’ preference for borewells has over the years ensured that the most existing open wells dried up. As Bengaluru expanded without regulation, paved surfaces increased dramatically, filling up recharge pits and open areas.

Recharge potential

Varthur-based environmental activist Jagadish Reddy notes that the small water bodies, the small tanks and ponds play a major role in recharging the ground water locally. “Preserving them was paramount across the 110 villages, but the real estate boom and haphazard development have ensured that these are completely gone,” he notes.

Vast stretches of Mahadevapura, Sarjapura, Anekal and other outlying areas had these water bodies in plenty. “Lake rejuvenation projects do not cover these. These ponds and small tanks, extending to half acre, one acre, half gunta, used to support the local irrigation systems. Encroachment of canals and narrowing of Rajakaluves by real estate players wiped them out.”

If this realisation had dawned on the government, last year’s copious rains would have filled up these water bodies, replenishing the shallow aquifers in the process. “Wherever possible, the small ponds should be reopened now to help the water security of the areas, particularly the 110 villages,” says Jagadish.

Cauvery supply

This seems to be the only sustainable way forward. The BWSSB might be offering the Cauvery Water Supply Scheme Stage V as a potential solution. But not many people see it as viable due to the steep connection costs. Neither are the real estate developers ready to bear the expenses.

The Cauvery 5th Stage was conceptualised to supply an additional 775 Million Litres Daily (MLD) of water to the 110 villages spread across Mahadevapura, Dasarahalli, Rajarajeshwari Nagar, Bommanahalli and Byatarayanapura.