Dhaka Water Supply and Sewerage Authority (Wasa) assigned the Institute of Water Modelling (IWM) to conduct a two-year long survey on the overall situation of water in the city in November 2004.

The Institute has finalised the report, that shows the ground water level in the capital is depleting by two to three metres a year, and is expected to be published next month.

The ground water level in the city, it has been recorded, has gone down by 29 metres in the last ten years.

Water was available at a depth of 27 metres from the surface in 1996, but the depth varies in different areas and on an average it is now at 56 metres from the surface.

Although experts sound alarm on conserving and preserving the environment of the capital, ground water dependency and extraction, ignoring implications, is increasing day-by-day.

Wasa taps around 60,225 crore litres of water from the ground a year using 441 Deep Tube Wells (DTW), with a daily average extraction of 160 to 170 crore litres.

Wasa extracts water from the upper aquifers up to 200 metres from the surface in the city, while the DTWs of various capacities have increased considerably and stands at 1,326 at present.

Experts warned if depletion of groundwater continues for the next few years there is likely to be a big change in soil structure resulting in land subsidence, and cited the example of Bangkok in Thailand where land subsided about 13 cm because of a drop in the water table by several tens of metres in a few decades. Following this incident Bangkok decreased the dependency on groundwater.

"The manner in which ground water is depleting and if the pressure on this source of water is decreased by at least 50 percent right now, Dhaka would experience land subsidence at anytime," an expert said.

The IWM report indicates Dhaka's population growth would be doubled, reaching 24 million by 2025, complicating the situation more.

The survey report suggested alleviation of pressure on the upper aquifer and the use of alternative water sources, from rivers like the Padma, Meghna and Jamuna.

The experts said that groundwater base system in Dhaka would not sustain for long, with the limited number of water bodies. Moreover, developers, real estate companies and city dwellers building houses in open spaces the city, and lake and river encroachment in and around the city have worsened the situation.

"Groundwater does not get recharged automatically as there is no open space to accumulate rainwater. It threatens the quantity and quality of water," said the Nurul Haque, Wasa's chief engineer.

"Apart from reducing extraction water from the ground, we should take steps to recharge groundwater artificially sending rainwater underground," said Haque.

Despite all these warnings and alarms Wasa has failed to find a strategy, immediate or otherwise to use alternative sources for water and save the environment.

Groundwater level was recorded at 28.15 metres from the surface in 1997, 30.45 in 1998, 31.86 in 1999, 34.18 in 2000, 37.78 in 2001, 41.87 in 2002, 46.24 in 2003 and 50.92 metres in 2004 in the capital.

Hedayetullah Al-Mamun, Wasa'a acting managing director said they were also worried about the matter and they too, want to lessen the dependency on the ground water gradually, but collecting water from alternatives sources involves a huge amount of money.

"After we officially get the report we will sit with the concerned offices and officials to chalk out a way to get out of this situation," said Al-Mamun.

"We need to find a quick solution to supplying city dwellers with drinking water on one side and maintain ecological balance on the other," he added.

He emphasised on implementing the second phase of Sayedabad water treatment plant that would produce and supply 22.5 crore litres of water everyday.