Groundwater table dips by nearly 2m

Survey shows water levels are at a depth of 6-10m beneath the ground in key localities

Balancing options: Experts suggest using open wells and borewells alternatively to preserve resources.

While the city’s wait for a good spell of summer showers continues, the groundwater table is witnessing a steady dip. In April, the water table declined by nearly two metres in various parts of the city when compared to same period last year.

According to a survey on water levels conducted by Rain Centre, a city-based voluntary organisation, the water table has dropped up to six metres below ground level in Nesapakkam, West Mambalam and Triplicane and beyond 10 metres in localities such as Mylapore and Adyar.

The varying water table in the localities across the city indicates the level of extraction of groundwater and the decline also depends on the soil condition in each area, Metrowater officials say.

 

For instance, Anna Nagar has had only a marginal dip in the water table in April.

The survey covered many areas in southern and central Chennai along the Adyar and Cooum rivers by monitoring water levels in 90 open wells identified per sq. km.

The rapid incease in the number of borewells has also added to the stress on groundwater.

Mathangi Narayanan, a resident of Okkiampet, said: “Last year, we had water in our open well because of bountiful rainfall in 2015 and good recharge through rainwater harvesting. But this summer, I am worried about the decreasing water level in the well probably due to overdrawal in the neighbourhood.”

Rain Centre director Sekar Raghavan said the dip in the water table in April was not alarming. “This could probably be due to the volume of water supply by Metrowater till last month. Moreover, this also indicates that people are not extracting from the shallow aquifer that is available in open wells and are instead digging deeper by sinking borewells and exhausting resources in deep aquifers,” he said.

 

Sustaining resources

Residents must alternate between tapping groundwater in open wells and deep borewells to sustain resources throughout the year. The cost for digging a 3.25 feet dia and 25 ft. deep open well is estimated to be ₹60,000 and that of 4.25 feet dia will cost ₹85,000, he said.