Evapotranspiration in poplar phytobarriers: Analysis of well hydrographs using the White method
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An important parameter needed for the engineering design of poplar-based phytoremediation systems is the rate of groundwater uptake by the trees (evapotranspiration of groundwater = ET G ). As part of a joint research project between the University at Buffalo and Motorola Solutions, approximately three hundred and forty-five hybrid poplar trees were planted to control groundwater migration at the Ischua Creek Habitat site in Machias, NY. During the early stages of tree development, standard methods for estimating ET G (e.g., eddy covariance, stable isotope) were not applicable because of the undeveloped canopy of the young poplars. Instead, the White method was applied, which estimates ET G based on measured diurnal groundwater fluctuations data and estimated specific yield. This thesis research explored the implementation of the White method for poplar-based phytobarriers and evaluated the hydrologic performance of the poplar trees using field data from active site monitoring conducted over a three-year period. Comparison of ET G values at different locations has supported the hypothesis that ET G values were greater for wells close to the barrier versus ET G values from wells distant from the barrier; this result was significant only for 2013, when the influence of the poplar system was discernable. The results of ET G demonstrated that groundwater flow at Ischua Creek Habitat site is being impacted by the phytobarrier. As poplar trees continue to grow and adapt to the environment, increased water usage is expected to cause more pronounced diurnal groundwater fluctuations pattern. Statistical comparison of ET G values close to the barrier over three years supported this increasing trend. Recommendations were developed for scaling the local measurements to the full system and for improving the implementation of the method.