A review on water security and management under climate change conditions, Windhoek, Namibia

Of the driest countries on the African continent, Namibia is the most arid in Southern Africa and water scarcity is perhaps its greatest challenge. Windhoek, the capital city, depends on surface water runoff; groundwater systems and recycling of grey water for its domestic, commercial and industrial water supply. However, due to high evaporation rate in the city, only 2% of the total rainfall ends up as runoff and inflow into the dams, plus another 1% that seeps into the groundwater as recharge. The city accounts for 15% of the country's population. The results show that the high population and its accompanying water demand has led to a heavy dependence on the groundwater system as precipitation has gradually decreased, both in quantity and frequency over the last thirty (30) years. The results further show that abstraction from the Windhoek aquifer is currently estimated to be 2 Mm3 per annum and is considered to be unstainable. This scenario led to a significant lowering of the groundwater table over the years. To sustain the water demand, the city has adopted artificial recharge into the aquifer. However, this has not been sufficient, and often the local authority has resorted to a drought index strategy; a water management strategy that restricts water usage. To manage groundwater with water security as a priority in an environment of climate change and a growing city population; more strategies of water storage and harvesting need to be adopted and not only rely on the dams and the Windhoek aquifer.