30 water pumps of Dhaka Water and Sewerage Authority (Wasa) already inundated by rising floodwater.

Water pipelines stretching over a few hundred kilometres and many reservoirs have also gone under water, posing a serious threat to public health.

According to media reports, floods have already affected more than 50 lakh people or half the total city population. People in 18 thanas of 22 are already marooned.

The Flood Forecasting and Warning Centre (FFWC) has forecast that more city areas may go under water in the next few days as four rivers around the capital, already flowing much above the danger mark, continue to swell.

ANH Akhter Hossain, managing director (MD) of Wasa, said the authorities have started to rush safe drinking water to the affected people by boat and rickshaw-van.

"As the situation in Khilgaon, Bashabo, Goran and Nandipara has worsened, we have started to supply water there at 14 points in portable tanks," he said. "We will also supply in 5-litre cans."

But the situation is still far from satisfactory. Many have already been attacked with diarrhoea and typhoid.

Wasa officials said although some pumps are now submerged, the authorities have not stopped using them.

"If we stop the pumps, dirty water will get inside the pipelines because of the vacuum created," the Wasa MD said. "We have to keep the water pressure in the pipelines high all the time as a protection against contamination."

Wasa has made special arrangements for uninterrupted power supply to the inundated pumps.

The flood-hit areas in the eastern part of Dhaka where people have been facing the water crisis include Swamibagh, Arambagh, Fakirapool, Gopibagh, Rampura, Badda, Sabujbagh, Motijheel, Kamalapur, Basabo, Khilgaon, Goran, Meradia, Mughda, Manda, Kajla, Rajakhali, Matuail, Jatrabari and Madartek.

On the western fringe, the worst affected areas are Lalbagh, Rayerbazar, Islampur, Bangshal, Shyampur, Faridabad, Swarighat, Sadarghat and Kamalbagh.

Basabo and Meradia are the worst hit areas. "We virtually are left without a single drop to drink," said Shayla Shabnam, a Dhaka University student in Basabo.

Pipelines have leaked and water now reeks of sewage.

"We bring drinking water in pitchers from our uncle's house in Tejgaon," said Ahmed Shafi, a Meradia resident.

Residents now purify water by using fitkiri (alum) and water purifying tablets. "The tablets adds a bad odour to water," said a local.

Many families have already left the inundated areas for higher ground.

Wasa has directed its staff to stay in the zonal offices even after office hours.

"They will monitor the situation and inform the head office in case of emergencies," a source said.