water Article Natural Pans as an Important Surface Water Resource in the Cuvelai Basin—Metrics for Storage Volume Calculations and Identification of Potential Augmentation Sites Robert Arendt 1,* , Christian Reinhardt-Imjela 1 , Achim Schulte 1, Leona Faulstich 1 , Tobias Ullmann 2 , Lorenz Beck 2,3 , Sandro Martinis 3 , Petrina Johannes 4 and Joachim Lengricht 4 1 Institute of Geographical Science, Applied Physical Science–Environmental Hydrology and Resource Management, Freie Universitaet Berlin, 12249 Berlin, Germany;
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[email protected]; Tel.: +49-30-838-63590 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 Citation: Arendt, R.; water stored in pans is often the only affordable water source for many people in rural areas. High Reinhardt-Imjela, C.; Schulte, A.; inter- and intra-annual rainfall variations in this semiarid environment provoke years of extreme flood Faulstich, L.; Ullmann, T.; Beck, L.; events and long periods of droughts.