Bangalore, India’s tech capital, is partway through an ambitious campaign to build a water culture – the ‘Million Wells for Bengaluru’ campaign. Started by the Biome Environmental Trust in July 2015, it is expected to run until 2025. The aim is to restore the city’s groundwater table through an ancient technique while providing livelihoods to local traditional well diggers, called Mannu Vaddars, in Karnataka.
Bangalore, one of the fastest growing cities in Asia, has no major river and long ago outgrew the nearest river, the Arkavathi. The Cauvery River brings the city 1,450 million litres of water a day, but at its closest point, it is 100km (63 miles) south of the city.
Biome wants people to value water availability and water structures and take responsibility for managing groundwater collectively, seeing it as a resource to be conserved and managed with community participation. They want people to understand that the whole community benefits if everyone recharges.
Renuka high school, in southeast Bangalore, used to have water trucked in, because that part of the city still lacks access to piped water. A cavernous, hand-crafted well has provided clean water since 2013 – enough to supply the school’s toilets, washroom and gardens. The well refills within two to three hours as water percolates in from Kaikondrahalli Lake – which was cleaned up in 2009 – topped up by rainwater collection from the school’s terrace.
The 14 ft (4.2 m) deep open well was dug by the traditional well diggers or mannu vaddars, specialists who learn by working alongside skilled elders. These open, shallow ‘recharge’ wells draw on higher aquifers that fill up rapidly when it rains, unlike the city’s 400,000 authorised deep borewells which draw water from deep aquifers below 60m (200ft) that take a long time to recharge.
One mannu vaddar digs, while the rest heave the soil out using plastic buckets. When soil lumps begin to show telltale pores made by tiny water rivulets, the mannu vaddars know they are at the edge of a shallow aquifer, which holds rainwater between 10 to 100ft (3 to 30m) beneath the Earth’s surface. Water then begins to seep out of the earth into the pit. The well-digger continues to dig for another 2.5-3m (8-10ft).
The process has remained unchanged for generations, except that now, wells are lined with pre-cast cement rings instead of stone blocks. Each ring has four one-inch holes to let water percolate from the aquifer; the stone blocks were arranged without mortar for the same reason.
It takes about three days for a team of seven or eight to dig a 9m to 12m (30-40ft) well, which fetches anywhere between 30,000 ($410) to 150,000 ($2,000) Indian rupees depending on the depth of the well, BBC reports. On average, each well-digger makes 1,200 Indian rupees ($16.40) per day, more than twice the average daily wage for a male urban worker in India.
Bangalore receives a lot of rain between April and November – 972 mm (3.2 ft) – with about 60 days of rain a year. But it doesn’t sink into the ground and recharge aquifers, because the city has paved so much of its surface – as much as 93% of the city. Rainwater runs down roads into sewers and inundates lower lying areas.
“In a natural state, with normal rainfall, between 3% and 10% of the city’s rains percolate into underground aquifers,” says Vishwanath Srikantaiah, a water conservation expert who leads Biome. “Once you start building on the soil, you start to ‘crust’ the ground and kill that 10%, bringing percolation down to zero.”.Bangalore already has around 10,000 open wells, made by earlier well-diggers.
“We estimate that if the mannu vaddars can help the city dig one million wells, we can achieve 50-60% percolation of rainwater and avoid urban flooding,” and that would bring 1,400 million litres of water a day from the city’s shallow aquifers. And it would be much cheaper – water needs to be pumped up a mere 6m (20ft) from the open wells, while it has to be pumped up 300m (984ft) from the Cauvery. Thus the water from the open wells is around 1% of the price of bringing water from the river.
“Traditional well-diggers who were part of a participatory aquifer mapping process in south-east Bangalore demonstrated a keen awareness of pre-existing wells, soil types, presence of rocky layers and other traits of the region’s aquifers,” says Shubha Ramachandran, a water sustainability consultant with Biome. “This oral lore of the city’s open well history can be invaluable.”
Demand for the services of the mannu vaddars is growing – the Bangalore Water Supply and Sewerage Board now mandates compulsory rainwater harvesting and groundwater recharge structures in every house and community, reports the BBC.
“The unique well-digging tradition of the mannu vaddars can ease Bangalore’s water woes,” says Srikantaiah. “With their help, areas of the city with shallow aquifers can create a river beneath the ground, rather than pump a river up to the city.”
Sources:
The Answer to India’s Water Crisis: Community. Shubha Ramchandran at TEDxBangalore, Dec. 20, 2019
TEDx Biome. Urban Waters, Bengaluru. Oct. 17, 2020
Biome Environmental Trust website.
The Indian megacity digging a million wells. BBC Future Planet, Oct. 7, 2020