Bengaluru summer | Apartments breaking free from tanker water

Ahead of summer, an AI-based analysis of the city’s groundwater data has predicted water shortages in 65 wards. These include Hebbal, Sanjaynagar, Jalahalli, Peenya, Horamavu, Ramamurthynagar, Koramangala, Nagarabhavi, Vijayanagar and Kengeri. The Bangalore Water Supply and Sewerage Board partnered with the Indian Institute of Science for the study.

Responding to the report, water conservationist S Vishwanath said the priority should be to ensure that every household in Bengaluru is connected to the piped water network. “Once that happens, groundwater can become a supplement,” he said. He added that some large gated communities have managed to improve the water table, as they have more open land and rooftop areas for rainwater harvesting. However, he emphasises the golden rule of groundwater security: recharge, but draw less than you recharge so there is always a reserve.

Self-sufficient

Century Saras, an apartment complex of 128 flats in Yelahanka New Town, does not have a piped water connection. Yet it does not rely on tanker water, thanks to the water management measures the apartment has followed since residents began moving in around 2016, says Satish Mallya, resident and president of the Bangalore Apartments’ Federation (BAF).

In 2021, the apartment received a commendation certificate as a ‘Water Donor’ from World of Water, Bengaluru, for saving about one crore litres of water annually for the city. This includes around 72 lakh litres through its sewage treatment plant, 18 lakh litres through aerators, and 12 lakh litres through rainwater harvesting. Last year, the Karnataka government recognised its sustainability efforts.

“We have eight recharge wells, each about 20 metres deep. During the rains, water from the terrace catchment area of one block is diverted into rainwater harvesting tanks. This meets nearly three months of our water requirement,” says Mallya. The system saves residents about Rs 1 lakh a year that would otherwise be spent on tanker water.

The apartment currently meets its freshwater demand through borewells – two are functioning, and efforts are under way to rejuvenate two that have dried up.

The apartment also installed an open well last year. According to Mallya, the groundwater table in the area is relatively healthy, at around 15 m in the shallow aquifers and about 150 m in the deeper aquifers.

Tanker use down

Until four years ago, Sobha City, a complex of 1,958 apartments on Thanisandra Main Road, depended on more than 20 water tankers a day. Today that number has come down to five or six. The change began when the complex started digging recharge wells across its 36-acre campus, says apartment association president C Subramanyam. They now have about 25 recharge wells, including two in each of its six blocks, built at a cost of over Rs 30 lakh. “Last year alone we added 19 wells. Earlier we had dug five, but the results were slow," he says.

Residents will assess how the system performs this summer and expand the recharge network if needed. “It also helps that we have large open green spaces where rainwater naturally percolates into the ground,” he adds.

Higher borewell yields 

Prestige Lakeside Habitat, a complex of 3,500 flats and 270 villas along Whitefield-Sarjapur Road, was spending between Rs 33 lakh and Rs 50 lakh a month on tanker water at the start of 2024. The campus has 24 borewells, but only five were working, meeting just 15% of its water needs. Following a camera inspection by Biome Environmental Solutions, it was found that seven more borewells could be revived with basic intervention. Project manager Shivananda R S says, “We built four recharge wells, each four feet in diameter and about 40 feet deep, to help recharge these borewells. After a few spells of rain, the yield from four of them increased.”

The apartment spent about Rs 12 lakh on the work and recovered the cost in less than four months as their tanker water dependency dropped. Satish Maram from the apartment association says they plan to add more recharge wells to support the remaining borewells and the aquifer.

Saving on costs

House of Hiranandani in Devanahalli has around 600 flats, 200 villas and 167 cottages. The 73-acre campus has more than 60 recharge wells and eight borewells that go 900 to 1,000 feet deep.

A few years ago, on Biome’s guidance, rooftop rainwater from one of the blocks was diverted into an existing sump. During the rainy months, this stored rainwater is treated and supplied to residents. This has reduced dependence on borewells and saved about Rs 12,000 a month in pumping costs. Overflow from the sump is channelled into stormwater drains and recharge wells across the campus, helping replenish groundwater and sustain borewell yield.

They now plan to bring four unused open wells back into use. “They still hold water, which indicates the presence of shallow aquifers,” says Shivananda.

Showcase of best water practices

Parisara Habba, an event showcasing water conservation and management practices, will be held on March 10 from 10 am to 6 pm at Indira Canteen, Sonnappanahalli, off Bangalore Airport Road. The event will highlight how Devanahalli and Hunasamaranahalli towns in north Bengaluru faced less water stress last summer than many other areas. The model focuses on reducing dependence on deep borewells and instead using water from shallow aquifers. Shivananda says these aquifers recharge faster, thanks to treated wastewater pumped into the lakes in the area by the H N Valley project implemented by the Minor Irrigation Department. The model is now being replicated in Doddajala.