A living laboratory
The Coweeta Hydrologic Laboratory, established by the U.S. Forest Service in 1934, is a 5,400-acre basin in the Appalachian Mountains dedicated to a single question: how do forests affect the water we drink? The entire valley is a natural laboratory. Its geology features a solid bedrock base, which ensures that nearly all precipitation that falls within the basin's ridges must exit through a single stream. This unique setup allows scientists to precisely measure the water budget of an entire ecosystem.
The core of the research involves treating whole watersheds as giant experiments. Over the decades, researchers have subjected different watersheds to various treatments, from clear-cutting and prescribed burns to converting hardwood forests to white pine plantations., Each of these manipulated watersheds is compared to designated "control" watersheds, which have remained undisturbed since 1927. At the bottom of each stream is a weir, a small dam with a V-notch, that continuously gauges the volume and rate of water flowing out. Combined with a network of rain gauges, this system provides a meticulous accounting of water entering and leaving the forest. One early, definitive finding was that an acre of white pine uses 250,000 more gallons of water per year than an acre of native hardwood forest, significantly reducing streamflow.