National Park Service hydrologist Erin White likes to call Yellowstone “America’s first water park.” It’s home to the headwaters of multiple major rivers and hundreds of waterfalls. Thousands of geysers, mudpots, and hot springs—heated by an underground supervolcano—gush, bubble, and boil in the national park’s 2.2 million acres, too. These waters comprise one of the largest nearly intact temperate ecosystems in the world. So when a series of lightning strikes sparked the 1988 fires that torched