Long-term watershed monitoring at the Hubbard Brook Experimental Forest in New Hampshire helps scientists detect increasing forest water use.

Careful monitoring of precipitation and streamflow over more than 65 years at the Hubbard Brook Experimental Forest in New Hampshire has allowed scientists to track the amount of water forests use for transpiration and evaporation. Long-term trends in these hydrologic data indicate that forest water use increased by almost 35 percent between 2010 and 2020. About half of the increase can be attributed to a drier atmosphere and the other half can be attributed to increasing forest productivity. These results raise questions about how broad the trend is, and concerns about excessive forest water use, given that these headwater streams supply water to communities downstream. Higher rates of forest water use could reduce recharge of groundwater that feeds streams and rivers. New studies at Hubbard Brook are tracking how soil moisture and groundwater are responding to greater forest water use and are exploring exactly why more water is moving through trees and being lost to the atmosphere.