This astronaut photograph shows the white, salt-covered floor in the northwest corner of the Etosha Pan, a great dry lake in northern Namibia, surrounded by multicolored water features. In a rare event shown in this image, rainwater has flowed down the Ekuma River—which appears as a blue line within the light gray-green floodplain—and fills a lobe of the lake with light green water.
Two rivers, the Ekuma and Oshigambo, transport water from the north down to the Pan. Other smaller lakes hold red and brown water, a result of the interplay of water depth and resident organisms such as algae. The algae color varies depending on water temperature and salinity. A similar process is observed in pink and red floodwaters when they pond in Lake Eyre, a mostly dry lake in Australia. In Lake Eyre, researchers know the color is indeed due to algae growth.