A groundbreaking simulation from Princeton and the University of Arizona reveals that groundwater flow paths travel much farther and deeper than previously understood. By tracking water across 3 million square miles, researchers discovered that raindrops and snowmelt can travel underground for several hundred kilometers and spend up to 100,000 years in the subsurface before emerging into freshwater streams.
The study highlights two transformative findings regarding our water systems:
- Nearly 90% of US watersheds exchange water with their watershed neighbors.
- More than half of the water in 56% of subbasins originates from deep aquifers (10 to 100 meters deep), debunking the myth that deep water is isolated from surface streams.
These findings have critical implications for managing contamination and climate change. Because groundwater flow paths are so extensive, pollutants like nitrates and "forever chemicals" (PFAS) can persist in the environment for decades or centuries as they take these long journeys to surface water.
