Precipitation variations and shifts over time: Implication on Windhoek city water supply

Abstract

Abstract The scarcity of freshwater is a growing concern around the world, especially in the developing world and is increasingly threatening human survival in less affluent parts of the world. In arid and semiarid regions, freshwater resources are imperative for the survival of populations as well as development activities in urban centres. Preceding assessments for potential solutions have underestimated the scarcity of water by failing to capture main trends of precipitation and the extent of drought periods. This paper aims to investigate rainfall trends for the City of Windhoek, Namibia. A century scale is examined by reconstructing historical precipitation records, and future trends are subsequently estimated and interpolated using Ordinary Kriging in ArcGIS 10.3. Kriging responds and handles spatial correlation much better for observed data points. The results show locations that receive high rainfall and potential periods for harvesting rainwater. The findings further show that the periods of high rainfall are shorter, and after each high rainfall stretch, a long period of lower rainfall follows immediately. Each low rainfall period is anticipated to last longer than the previous one. These scenarios are highly significant for urban managers in dryland cities such as Windhoek, as they demonstrate when water would need to be extra sparingly managed. This study highlights the need for better water management strategies, if cities in dry climates are to survive the anticipated future water crises.