Summer has officially set in, and the average water table is now at a depth of 3.75 m in the city and has not witnessed much of a dip across the city.
According to data available with the Metrowater, the average water table level has gone from 3.31 m in January to 3.75 m in February, only a marginal dip of 0.45 m. The city’s average water level was at a depth of 5.57 m below ground level during February 2021. The water table has improved by nearly 1.81 m compared to last year.
A bountiful northeast monsoon, which extended till mid-January and sufficient piped water supply had led to less groundwater extraction in most parts of the city. This has sustained the reserves till early March unlike previous years, noted groundwater experts and hydrogeologists.
The water table is high in several parts of the city. It is available at a depth of nearly 1.94 m in Adyar zone and has depleted by only 0.23 m compared to January. The water table remains at 4.95 m in the densely-populated Thiru. Vi. Ka. Nagar. Groundwater level varies at a depth of 2.6 m to 4.70 m in most zones of the city.
With abundant rainfall and inflow from rivers upstream, the city reservoirs have a total storage of nearly 84% of their capacity. Metrowater is supplying nearly 1,011 million litres of water a day (mld) to the city. Of this, nearly 922 mld is being provided through pipelines.
While piped water supply had reduced dependence on groundwater, the water agency’s recent survey found that 75-80% of the rainwater harvesting structures helped recharge the water table, according to officials.
The high water table in many areas has also delayed a project of Rain Centre, a city-based voluntary organisation, to sink recharge wells in 40 locations.
Sekhar Raghavan, director, Rain Centre, said “We were planning to sink recharge wells in road corners that had water stagnation during the monsoon. But, we found that the shallow water table was within a depth of 2.6 m-3 m in areas such as Anna Nagar and Mogappair. Usually, the water level depletes to 4 m in March in these areas.”
City residents are not tapping into the shallow aquifer available within a few feet from ground level, and this has led to groundwater saturation. “Open wells can be used to draw groundwater available at the shallow layer. The benefits of rainwater recharge could be passed on from the shallow layer to the deep aquifer if slotted casing pipes are used in borewells,” he said.
In households with space constraints, residents may sink tubewells at a depth of 30-35 feet to extract water from shallow layers, Mr. Raghavan added.
