Water management in Dhaka, the capital of Bangladesh and a city with 20 million inhabitants, faces numerous challenges such as flooding, poor service quality, groundwater depletion, inadequate sanitation, polluted river water, unplanned urban development, and the existence of large slums where more than one third of its population lives. Residents of Dhaka enjoy one of the lowest water tariffs in the world, which limits the utility's capacity to invest. The utility in charge of water and sanitation in Dhaka, DWASA, addresses these challenges with a number of measures. It says that in 2011 it achieved a continuous water supply 24 hours per day 7 days a week, an increase in revenues so that operating costs are more than covered, and a reduction of water losses from 53% in 2003 to 29% in 2010. For these achievements DWASA, got a "Performer of the Year Award" at the Global Water Summit 2011 in Berlin. In the future DWASA plans massive investment to replace dwindling groundwater resources with treated surface water from less polluted rivers located up to 160 km from the city. In 2011 Bangladesh's capital development authority, Rajdhani Unnayan Kartripakkha, made rainwater harvesting for new houses mandatory in an effort to address water scarcity and reduce flooding. History The first piped drinking water system in Dhaka was established in 1874 by Khwaja Abdul Ghani, the aristocrat that ruled Dhaka under the British colonial authorities. The system was fed by a water treatment plant in Chadnighat near the bank of the river Buriganga. After independence from the British in 1948 the Department of Public Health Engineering of the Pakistani government was in charge of drinking water supply as well as sanitary sewers and storm-water drainage. Dhaka WASA (Water Supply & Sewerage Authority) was established in 1963. In 1989, the storm-water drainage system of Dhaka city was handed over to DWASA. In 1990, the service area was extended to include Narayanganj city. In the early 1990s the World Bank had said it would only provide a loan for water supply in Dhaka if the utility would enter into a public-private partnership with an international water company. When this was rejected, it asked that revenue billing and collection should be outsourced to a private company for at least one service area on a pilot basis, and that DWASA should be transformed into a commercially oriented utility. The outsourcing in one service area was done