Dhaka (CNN) - Life in low-lying Dhaka can be a paradox. Flood waters rise up to a meter in the monsoon months, but there is an ongoing shortage of clean drinking water.

The Dhaka Water and Sewerage Authority (DWASA) is working with WaterAid in some of the country’s biggest and most unsanitary slums to improve access to safe, legal drinking water connections, and build toilet units.

One of their success stories is the Uttar Kalshi slum. Practically an island, it has one entrance point and is surrounded on all sides by water. It is the first slum in the country to receive a legal water supply.

Beyond the slums, Dhaka suffers from polluted surface water, the result of effluent from the leather tanneries, garment industry and excess of pollution in the city.

Almost 90% of the water consumed in Dhaka comes from the city’s underground resources. But Dhaka is now running out of this water, with levels dropping by up to three meters a year.

DWASA is therefore turning to water treatment plants to make more use of the abundant, but heavily polluted, surface water.

So far, there is only one surface water treatment plant in Dhaka, which provides around 10% of the daily water demand. A second treatment plant in Saidabad is now being built with the help of Danish and French contractors. The plant should be fully functional by the end of the year.

The city is looking ahead, with additional plans in place for three more plants. The aim is to use 30% of underground water and 70% of surface water by 2021.