| Category: Health & Beauty: Environmental Health |
One of Asia’s fastest-growing cities has no major river and its deep groundwater is running out, but an age-old practice could help the city find water.
The school is housed in a nondescript two-storey building in a densely populated district of south-east Bangalore. Pillars painted in the orange, white and green of the Indian national flag add a dash of colour below the tall tower blocks that crowd around Renuka High School.
In many ways this district is very much a typical part of the modern megacity of Bangalore, India’s capital of tech. But in one important way it is still an island – this outlying region of the fast-developing city lacks crucial access to piped water.
But in the school’s grounds, an ancient practice of well-digging has been revived to quench the area’s growing thirst. The school’s cavernous, hand-crafted well is part of a grander plan to build one million such wells throughout Bangalore. It is an epic task, but this challenging, age-old practice of well-digging could help to protect the city from the stresses of climate change.
Parched city
Bangalore’s status as one of the fastest growing cities in Asia has come at a steep price. The closest river is the Arkavathi, which Bangalore outgrew long ago. The Cauvery River is a lifeline to the city, supplying 1,450 million litres of water a day, but it flows 100km (63 miles) south of the city at its closest point.
One alternative water supply is groundwater. The city has 400,000 authorised deep borewells, though many are bone-dry due to over-exploitation. These borewells draw water from deep aquifers that trap water between the fissured rocky layers of the earth below 60m (200ft). The percolation to such depths is slow and recharging these deep aquifers can take years – which, for a rapidly expanding city, is not feasible.
“Bangalore’s topography is not conducive to having abundant water supply,” says Hita Unnikrishnan, of the Sheffield Urban Institute, who studies the history of community water resources in Bangalore.
Yet the problem is not a lack of rainfall. Bangalore receives a substantial 972mm (3.2ft) of average annual precipitation between April and November, with around 60 rainy days in a year.
Where does all this water go? The answer can be found in a study by researchers of the Centre for Ecological Sciences at the Indian Institute of Science, which points to a more than tenfold increase in paved surfaces in Bangalore between 1973 and 2017. An estimated 93% of the city has been paved.
Precious rainwater that could recharge the aquifers instead flows down the buildings and tarred roads of the city as surface run-off, choking sewers and inundating the low-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 the not-for-profit Biome Environmental Trust, which leads the One Million Wells for Bangalore initiative. “Once you start building on the soil, you start to ‘crust’ the ground and kill that 10%, bringing percolation down to zero.”
So the precious rainwater that could recharge the aquifers instead flows down the buildings and tarred roads of the city as surface run-off, choking sewers and inundating the low-lying areas. It is a problem that climate change is predicted to make worse in the coming decades.
Striking water
Until a few years ago, water tankers travelled from Bellandur or Iblur, about 4km (2.5 miles) away, along busy roads to supply Renuka High School with water. The tankers delivered a total of 1,000-litres of deep borewell-drawn water once or twice a week.
It was a cumbersome process, and the school authorities questioned quality of the tanker-supplied water. Ground water in many areas of the Bangalore Urban District is contaminated by sewage, industrial pollution and high nitrate levels. The local Kaikondrahalli Lake, too, was troubled by a history of sewage and rubbish dumping.
There was one realistic alternative left. In 2013, Renuka High School engaged the services of traditional well diggers called “mannu vaddars” to dig a 14ft (4.2m) deep open well.
Well-digging, repair and maintenance is a highly specialised occupation, and one fraught with danger. Mannu vaddars work alongside skilled elders, learning the technique passed down the generations. The elders of the mannu vaddars have practiced their craft without loss of life or limb as they dig deep into the earth, with little more than shovels.
These wells are not like the narrow boreholes that drain the lower aquifers, but open, shallow “recharge” wells that access higher aquifers that fill up rapidly with the rains.
If the mannu vaddars can help the city dig one million wells, we can achieve 50-60% percolation of rainwater and avoid urban flooding – Vishwanath Srikantaiah
Digging such a well is easier said than done. Present-day landowners rely on the services of a hydrogeologist and the ancient Indian architectural practice of “vaastu shastra”, which seeks to align design principles with the elements of nature, to pick the well’s location. Once the right place has been identified, the mannu vaddars use a string to measure the radius of the cement ring used to line the earthen walls of the well. Before the ground can be broken, a prayer is offered to the water goddess Gangamma.
One mannu vaddar is assigned the task of digging, while the rest heave the soil out using plastic buckets. If the soil in the area is loose, a custom-fabricated metal mesh is placed on the inside of the pit to reduce the risk of the walls collapsing in as the digging progresses. The mesh is removed after the digging is done, to make way for the cement rings.
When the soil lumps at the bottom of the well begin to show telltale pores made by tiny water rivulets, the mannu vaddars know they are nearly there. 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). It is hard and tedious work.
Apart from the lining materials used – cement instead of stone – the process is much the same as it has been for generations. One hundred years ago, the stone blocks lining the well were arranged without mortar so the water could percolate from the aquifer through the gaps. Now, pre-cast cement rings have taken their place, each with four one-inch holes to let the water in.
It takes around three days for a team of seven or eight mannu vaddars to dig a 9m to 12m (30-40ft) well. Father-son, brothers, uncles and cousins come together to form teams of mannu vaddars, and their efforts and profits are shared equally.
Digging a well fetches anywhere between 30,000 (£309/$410) to 150,000 (£1,500/$2,000) Indian rupees depending on the depth of the well. On an average, each well-digger makes 1,200 Indian rupees (£12.25/$16.40) per day, more than twice the average daily wage for a male urban worker in India.
“I can guarantee the success of any well I dig. I charge for the well only if it hits water, and there never has been a situation when it hasn’t,” says Pedhanna from Yellammapalya, a village of 75 well-digging families on the outskirts of Bangalore.
Million wells
Ever since the mannu vaddars built the well at Renuka High School, an equivalent of the erstwhile 1,000-litre tanker load of water was pumped from the open well each day, in two 500-litre batches –enough to supply the school’s toilets, washroom and gardens. The well refills within two to three hours of pumping, aided by a rainwater collection system from the school’s terrace.
The water level in the well coincides with that of the lake – which went through a thorough environmental clean-up in 2009 – according to the seasons. Some of the lake water percolates through the soil into the school’s well, with the soil between the lake and the well acts as a natural filter.
Renuka High School is among the many communities turning to sustainable water management practices through work with the Biome Environmental Trust. The trust’s Srikantaiah estimates that Bangalore already has around 10,000 open wells, the handiwork of the ancestors of today’s well-diggers. But there is a long way to go to the one-million-well target.
“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,” says Srikantaiah. That would bring 1,400 million litres of water a day from the city’s shallow aquifers, he calculates.
The skills of the mannu vaddars are crucial to this effort, not just in terms of labour but knowledge. “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 Environmental Trust, who works closely with the well-diggers. “This oral lore of the city’s open well history can be invaluable.”
As well as being reliable, this water is much more affordable. In open wells, the water needs to be pumped up a mere 6m (20ft) to the surface. Water from the Cauvery river, on the other hand, has to be pumped up 300m (984ft) to reach Bangalore. As a result, the water from the open wells is around 1% of the price of bringing water from the Cauvery.
The mannu vaddars are at the centre of this shift towards historic water practices in Bangalore, one well at a time. And demand for their services is growing – the Bangalore Water Supply and Sewage Board now mandates compulsory rainwater harvesting and groundwater recharge structures in every house and community. It suggests there could be hope for more regular work for the mannu vaddars, as well as promising news for Srikantaiah’s dream of a million wells.
“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.”
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~ Via BBC |
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