Incipient capture of an endoreic system: Geomorphology and numerical simulation of the Okavango mega-fan, Botswana

Subtropical endoreic wetlands are major water and biodiversity resources. Their existence relies on a subtle balance between internal and external factors. Understanding the effects of each of these factors is key to forecasting the evolution of endoreic basins worldwide. The Okavango Delta (Botswana) is emblematic of such systems. Situated in the Kalahari desert, its dynamics rely on an annual flood sourced from Angola. We show from geomorphological observation of the drainage system that capture of the Okavango River network through late Holocene regressive erosion from the Cuando river is incipient, likely initiating the loss of endoreism. Numerical simulations of such capture provide insights on the potentially upcoming reorganization of the river network that will modify the distribution of water resources and ecosystems.