Dhaka's groundwater level at the lowest in 11 yrs

 
By Pinaki Roy
Last Updated: Saturday 04 July 2015

Low on water
Little groundwater recharging a cause
Down to Earth
groundwater level in Dhaka has dropped to 61.18m below the surface putting the sprawling metropolis at risk. A recent study by the Bangladesh Agricultural Development Corporation (badc) has revealed that Dhaka's groundwater table has gone down by 35m in the past 11 years.

According to the Dhaka Water and Sewerage Authority (wasa), the groundwater table was at 11.3m below the surface in the 1970s and at 20m in the 1980s. However, water level has drastically fallen since 1996 (see graph Low on water). Between 1996 and 2007, the city's groundwater level declined at a rate of over three metres a year.

badc researchers blame it on the city's increasing population and little groundwater recharging over the years. Most of the city's wetlands and river banks have now been encroached for construction, barring full recharging of groundwater in the monsoons, say the researchers.

Unchecked surface water pollution has also prompted people to depend on groundwater heavily; the number of deep tube-wells in the city has gone up from 234 in 1998 to over 400 now.

The demand for water in Dhaka--the world's fifth densely populated city--is more than 2,000 million litres a day (mld); it was 1,500 mld in 1998, say sources at wasa.

Since the city's three water treatment plants fail to meet the requirement, people depend on deep tube-wells for 80 per cent of their needs.

The fast sinking water table will not only affect the city's future water needs, but also create a vacuum in the aquifer, warns Khandakar Fazal Hasan, chief geologist of badc. "This will also increase the risk factor during earthquakes and could lead to subsidence of the clay soil plate on which Dhaka is situated," says Hasan.

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