The U.S. and Japan may be plunging into a nasty trade war, but that hasn’t discouraged the folks at the Interstate Commission on the Potomac River Basin (ICPRB). They’ve found a sister for their lonely Potomac: Japan’s Arakawa River. Under a recent “Sister River Agreement,” Japanese and American officials will trade information about their rivers, watersheds, and ecosystems. So far, the Arakawa seems to be a worthy sibling for our noble river. She’s more aggressive than the Potomac; her name translates as “Violent River,” and she’s an infamous flooder. But she, too, rises in the forested mountains, cascades eastward, and flows through the heart of the capital city. And, perhaps most important for Washingtonians, cherry trees from the Arakawa’s banks were uprooted in 1912, shipped to America, and replanted along the Tidal Basin.