Supplying water to a water-stressed city: lessons from Windhoek

摘要

Windhoek, the capital of Namibia, is located in a semi-desert region, a long way from the sea and from its main surface water and groundwater sources. The city's population (a significant proportion of which lives in informal settlements) is growing. It has however been successful in meeting the water needs of its citizens, and has done so by working on several different fronts. Admittedly, part of the city's water supply is brought in from dams located some distance away from the city and, as is fairly conventional, these supplies supplement local groundwater sources. These resources are insufficient however, a problem that the City of Windhoek (CoW) has strived to address by reducing water demand on the one hand and increasing supply sources on the other. One of the major innovations is the use of dual wastewater reuse loops. In the first place the city has a reticulation system providing treated wastewater for the needs of parks and gardens. After been blended with treated surface water and sent to the city's drinking water system, a large part of this treated wastewater is used to provide drinking water however. The surplus water from rainy years is then injected into the underlying aquifer to ensure a backup supply source for dry years. In this way, as much as one quarter of the city's water needs is provided through wastewater reuse loops. Other valuable insights are to be gained from the analysis of social and cultural contingencies and their impact on the viability of water supply projects.