Salon: Analyzing approximately 15.9 million satellite images taken over a period of more than three decades, researchers at the University of North Carolina at Chapel Hill, the University of Pittsburgh and Colorado State University discovered that of the more than 108,000 kilometers (roughly 67,000 miles) of rivers at least 60 meters (197 feet) wide studied throughout the country, 56% appeared predominantly yellow and 38% appeared predominantly green.

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