Abstract
Numerous ephemeral rivers and thousands of natural pans characterize the transboundary Iishana-System of the Cuvelai Basin between Namibia and Angola. After the rainy season, surface water stored in pans is often the only affordable water source for many people in rural areas. High inter- and intra-annual rainfall variations in this semiarid environment provoke years of extreme flood events and long periods of droughts. Thus, the issue of water availability is playing an increasingly important role in one of the most densely populated and fastest growing regions in southwestern Africa. Currently, there is no transnational approach to quantifying the potential storage and supply functions of the Iishana-System. To bridge these knowledge gaps and to increase the resilience of the local people’s livelihood, suitable pans for expansion as intermediate storage were identified and their metrics determined. Therefore, a modified Blue Spot Analysis was performed, based on the high-resolution TanDEM-X digital elevation model. Further, surface area–volume ratio calculations were accomplished for finding suitable augmentation sites in a first step. The potential water storage volume of more than 190,000 pans was calculated at 1.9 km3. Over 2200 pans were identified for potential expansion to facilitate increased water supply and flood protection in the future.
Highlights
The Iishana-System is part of the western CB (Cuvelai Basin), which crosses the border between southern Angola and northern Namibia
1.2 million people live in this region (34% in Angola and 66% in Namibia) [3,21,36]
The study area is bounded by the Kunene River and Okavango River (Angola) in the north and by the Etosha Pan (Namibia) in the south
Summary
The Iishana-System is part of the western CB (Cuvelai Basin), which crosses the border between southern Angola and northern Namibia. The basin is one of the most densely populated areas in southern Africa; around 40% of all Namibian inhabitants live in this region. The high population density is expected to increase drastically at a growth rate of 1.4% in the several years [1]. Projections for the year 2041 anticipate a population count 27% higher than what exists today [2]. One factor driving this growth is the presence of slightly more fertile soil than in the rest of the country [3]. The cultivation of rain-fed sorghum and millet and the practice of stock farming are the most important sources of rural income [4,5]
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