More than half a percent of Earth’s nonglaciated land surface—about 773,000 km2—is covered with rivers and streams, according to a new analysis of satellite images. The estimate, which appears today (June 28) in Science, is about 44 percent higher than the previously accepted number.
“If you look around the world, rivers look different from place to place,” coauthor George Allen of Texas A&M University tells Gizmodo. “They might be braided, or sinuous, or meandering. And for the most part, current technology doesn’t take into consideration the actual morphology of rivers. This data set is the first of its kind to do this at a global scale on high resolution.”
Allen and Tamlin Pavelsky of the University of North Carolina, Chapel Hill, used software to pick out and measure the surface area of rivers in images from NASA’s Landsat satellite. They found that Earth’s rivers and streams collectively cover an area about the size of Texas, which “implies that interactions between rivers and the atmosphere are likely greater than previously thought,” they write in their paper.
John Downing of the University of Minnesota Duluth who was not involved in the research tells Gizmodo that polluted rivers and streams can leak gasses such as methane and carbon dioxide into the atmosphere as they make their way to the ocean. Greater knowledge of river morphology can also help in predicting floods, he says.
“Rivers are so wonderful, but they can also be dangerous,” Downing says. “Water goes where it wants to go—so it’s good to know where it goes and how much area it’s covering.”