Sunglint illuminates the great Okavango delta in the Kalahari Desert region of Botswana, in a photo taken from the International Space Station in June 2014. The bright line of the Okavango River shows the annual summer flood advancing from the well-watered Angolan Highlands (upper margin) to the delta. These floodwaters slowly seep across the 150 kilometres of the delta, feeding forests and wetlands until they reach its lower margin in the middle of winter. Most of the river’s water is used up by the forests, or evaporates in the dry air. Only two percent of the water finally exits the delta. Okavango delta wetland supports high biodiversity in the middle of the otherwise semiarid Kalahari Desert, and is now one of the most famous tourist sites in Africa. (Nasa, CC BY-NC 2.0)