Watercycle of Windhoek (diagrammatically). Bron: City of Windhoek, 2006. When the main perennial rivers are national borders originating in the neighboring countries, long-term supply agreements cannot be 100% guaranteed. Large supply schemes are very costly and in certain regions not economical to implement for various reasons. In such cases well-planned use and reuse of water can play a vital role to sustainability. Amy et al. (2005) recommend a new perspective in water resources management, where all concerned, the wastewater and water engineer take the full hydrological water cycle into considera tion in order to provide sustainable water supply. Wastewater should be seen as a resource and natural treatment within the water cycle, like an aquifer. A reservoir or a river should be included in the recla mation/reuse approach where possible. The City of Windhoek adopted a similar approach over many years. The water cycle of Windhoek is shown diagrammatically in the figure above. National and local policies should support reuse of wastewater, taking the constraints of the region as well as the potential threats of waste water reuse into consideration. Active participation through educa tional programs is needed to encourage planners and engineers to design systems that cater for reuse or that can at any time be changed to a reuse scheme. The following principles for reuse and reclamation are proposed in Namibia in the following order of priorities: 1. Industrial: cooling water for power plants and oil refineries, process water, boiler feed, construction activities, concrete mixing 2. Agriculture: crop and commercial nurseries 3. Landscape: public parks, golf course, school yards, cemeteries, greenbelts, residential 4. Recreation/environment: lakes, ponds, marsh enhancement, stream flow augmentation, fisheries Pagina 67
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