As World Rivers Day approaches, cause for concern – and hope – for the planet’s waterways

"Overall, researchers estimate that 63% of the world’s longest rivers no longer flow freely and nearly half of all reaches have some level of fragmentation."

Photo: The Potomac River near Washington, D.C., which has seen dramatic improvements in water quality over the past few decades. Credit: David Malakoff for The Habibat Project

“Rivers,” the Canadian conservationist Roderick Haig-Brown once wrote, are like the “veins of the Earth,” serving as lifelines for people and countless other species as well. Witho…