STEMFLOW AS A CONTRIBUTING SOURCE TO EARLY RUNOFF

Panola Mountain Research Watershed (PMRW), located near Atlanta, GA, has been studied extensively for over 30 years. Earlier work by Richard Cary used geochemistry to separate storm hydrographs into four component hydrographs: rainfall, near-surface soil water, shallow groundwater, and deeper groundwater. During most storms, rainfall water was not a significant component of flow until relatively late in the storm despite bare rock in the upper reaches of the watershed. One potential source of water to the stream that does not have the geochemical signal of rainfall is stemflow, or water that flows down the stem and enters the soil at the base of the tree, where it contributes as near-surface soil water, and shallow groundwater. To investigate the potential for stemflow to contribute to early storm flow, four Yellow Poplar trees (Liriodendron tulipifera) with a DBH of over 30 cm were wrapped and caulked with a collar funneling the water through a tipping bucket measuring device. The tipping buckets were connected to an Arduino to save the time of each tip. The Arduino also measured rainfall. A GPS was used to synchronize the high resolution real-time clocks. The timing of stemflow compared to rainfall and streamflow will be used to evaluate stemflow contributions to runoff.