Having nearly exhausted the surface water resources this summer and failed to preserve its network of water bodies, Chennai now looks deep down for its needs. The city is literally digging deeper to quench its thirst.
From the days when a borewell of a depth of 100 - 150 feet was considered a luxury to cater to residents’ water needs, people are now digging second borewells of deeper level — sometimes 900 feet in the suburbs -— anxiously looking for a water resource that could sustain them for some more years.
On an average, a borewell contractor would get to drill 60 borewells in a month. Now, they get work orders for 80.
Along with the growing demand, rates have gone up too. Earlier, digging a borewell would cost ₹ 90/ft. The asking rate today can be ₹ 110/ft.
Reduced supply
As the water supply from Chennai Metrowater has dwindled to 500 million litres on alternate days, residents and government agencies are relying on groundwater to bridge the gap in supply as summer peaks.
The lack of rainfall has also meant a fall in groundwater table in the city, which now hovers 4 - 5 metres below the ground level. This has led to digging five - six inch wide borewells as deep as even 900 feet depending on the soil formation.
Ashok Thamburaj, a resident of Kalyanipuram, Pallavaram, recalled that he spent only about ₹20,000 to dig a 150-feet borewell a decade ago. “As that borewell went dry, I had to dig another borewell up to a depth of 250 feet for a good yield at a cost of ₹70,000,” he said.
S.Yuvaraj, a borewell contractor in Thiruvanmiyur, said: “We normally get 20 enquiries per week. Now, it has increased to 50 enquiries daily. But, we are able to dig only two borewells a day due to labour issues. As the city has exhausted two levels of the aquifer, we are now tapping the third level.”
According to borewell rig owners, people in South Chennai and outskirts such as Pallavaram and Chengalpet are sinking deeper borewells up to a depth of 600-900 feet as the terrain is rocky there unlike in north Chennai.
Borewells are dug at a depth of 500 feet in locations like Choolaimedu and Anna Nagar that have clayey soil.
Jr. D. Gunaseelan, secretary, Chennai Borewell Rigowners and Drilling Contractors Association, said:
“The demand for borewells has gone up due to rapid urbanisation and lack of water bodies. Deeper borewells up to 1,000 feet are being sunk using high-power, sensor-mounted rigs. A 300-feet borewell can be sunk within four hours. Sinking deep borewells in north Chennai would mean intrusion of seawater. Cost would also vary according to the soil condition due to the use of casing pipes.”
No official estimates
There are no official estimates of the number of borewells in the city. L. Elango, professor, Department of Geology, Anna University, said 40 % of Chennai is charnockite rocky terrain, where water is difficult to replenish. Those areas closer to rivers may encounter contaminated water in borewells.
Experts suggested that residents should alternately use regular wells and borewells to sustain groundwater.
Sekar Raghavan, director, Rain Centre, said though the Tamil Nadu Groundwater (Development and Management) Act states that permission must be sought to dig borewells, it is not being strictly implemented. “Rainwater can be harnessed properly only if we use slotted pipes (with holes) instead of casing pipes. This allows rainwater to percolate into the borewells,” Mr. Raghavan added.
