Tracing Water Recycling in a Temperate Forest

Hubbard Brook Experimental Forest

Even though Hubbard Brook Experimental Forest in New Hampshire has been monitored for almost sixty years, no one really knows how much water evaporates versus transpires from it. I describe this knowledge gap in the present tense, because even I couldn’t figure it out with a team of three Ph.D. hydrologists and four years of water isotope data. What happened was that when we tried, we found that the soil and canopy in Watershed 3 (the uncut region touching the right margin of the photo) aren’t detectably evaporating precipitation back to the atmosphere; they’re recycling it back into the earth. It is one of the first studies to use an isotope measure called deuterium excess to locate such recycling in the terrestrial flowpaths, not the atmosphere. Published in Hydrological Processes.