Swiss photographer Michel Roggo captured this image of Wadi Wurayah in Fujairah, United Arab Emirates, as part of his Freshwater Project, a four-year effort to document 30 rivers around the world.
A wadi is a desert stream that is typically dry for much of the year. In this case, Roggo hiked for miles through an arid landscape, and was then startled by the sound of moving water. When he visited, the wadi only had water in it for a few hundred feet before the channel returned to dust.
"There are fish that can survive when this water dries out completely, then when the water comes back they appear again. No one knows how they do this," said Roggo.
He added that vegetation can spring up around the wadi, and that many animals, from snakes to leopards, come to drink and look for prey.
Roggo and some local student photographers put on exhibits of photos from the wadi in the United Arab Emirates. "Local people couldn't believe this was in their country," he said.
"This water is, for those people, probably of more value than oil."
So far, Roggo has lensed about 20 rivers for his Freshwater Project, with the goal of making beautiful pictures and educating the public about the importance of protecting freshwater—also the goal of World Water Day (and National Geographic and partners' Change the Course campaign), held annually on March 22.
Roggo told National Geographic News that he has specialized in freshwater photography for about 25 years. He does not do any diving, and instead makes most of his photos via remote-controlled cameras, while standing on the shore. "I try to work fast to catch the spirit of different freshwater locations," said Roggo.
Roggo said freshwater habitats face many threats around the world, although there is still much to discover. "Every time I go out I spot something completely different," he said. (Related: "8 Mighty Rivers Run Dry From Overuse.")
—Brian Clark Howard