Tamil Nadu

Rain boosts city’s water table

Abundant rain this northeast monsoon has led to a remarkable improvement in groundwater level in the city with the average going up by nearly 3.12 metre in November compared to the previous month.

According to the data available with the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB), the groundwater was available at a depth of 2.3 metres in November in the city compared to 5.42 metres in October. Similarly, it has improved by at least one or two metres compared to November last year.

Adyar zone recorded the maximum improvement in water table in the city and groundwater was available at a depth of 0.54 metre. The densely populated Royapuram zone saw relatively less recharge as the water table stood at 4.81 metre in November.

The water table remained at 1 to 3 metres in most other zones in the city in November. Madhavaram, Thiru. Vi. Ka. Nagar and Teynampet zones are among those localities that have seen a considerable recharge as water level increased by 5 to 7 metres within one month.

The CMWSSB is collating the groundwater data through its real-time online monitoring system and digital water-level recorders in borewells sunk at 200 locations across the city.

Salinity down

Hydrogeologists and experts said the groundwater is available within one metre in some of the core areas and salinity has also reduced up to 70%. What made this year’s inundation different from 2015 floods was that shallow aquifer had become saturated even before the onset of northeast monsoon and was not caused by water discharge into rivers. There was not much space left for floodwater percolation.

Sekar Raghavan, Director, Rain Centre, said consistent and above normal rain since October last year, comfortable storage in reservoirs, copious drinking water supply through pipelines this year and better rainwater harnessing methods led to the improvement in the water table. Residents in many core areas did not draw groundwater for their needs and the reserves were available in plenty.

“In areas like R.A. Puram, where open wells usually have water level at 20 feet depth, had water at a depth of 7 ft. in August. It indicated that the rainwater recharge and percolation potential was limited and waterlogging was bound to happen by first spell of monsoon rains,” he said.

Residents must tap shallow aquifer through open wells or sink tube wells for a depth of 30 feet to deplete groundwater sources and help floodwater recede. Recharging deep aquifer through borewells was difficult and could be done by opting for slotted casing pipes, he added.

The government must consider water metering system for domestic consumers to motivate them to use shallow groundwater source.

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Printable version | Jan 17, 2022 4:48:34 AM | https://www.thehindu.com/news/national/tamil-nadu/rain-boosts-citys-water-table/article37847250.ece

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