Comparison of Sap Flow- and White's Equation-Based Estimates of Groundwater Evapotranspiration
Abstract
Estimates of evapotranspiration (ET) of groundwater are useful at sites where phytoremediation is a component of the remedial strategy and the management of contaminant plumes. Methods to quantify direct ET of groundwater rely on multiple lines of evidence but are often limited to the measurement of water table levels and analysis of diurnal trends (e.g., White's Equation and related derivative methods). In this study, sap flow was collected and combined with monitoring of groundwater levels during the entire growing season at a site located in the Atlantic Coastal Plain (Georgia, USA). Our objective was to quantify temporal variations in estimates of groundwater ET in a phytoremediation test plot consisting of approximately 370 trees at a creosote-contaminated source zone. Trees ranging from 8-cm to 9-cm in diameter were instrumented with thermal dissipation sap velocity probes connected to a recording data logger. Wells and piezometers screened across the water table located within and around the periphery of the stand of trees were instrumented with recording pressure transducers. Sap flow estimates using the Granier method varied from 1 to 3 L/d per tree in dry months to 1 to 15 L/d per tree during periods of frequent precipitation and high ET potential. Results show no clear or consistent relationship between estimates of groundwater ET derived from water table fluctuations and sap flow results during the entire period of performance. However, this approach provides an upper and lower bound of groundwater consumption and concomitant plant uptake of light-weight polycyclic aromatic hydrocarbons.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.H12B..08W
- Keywords:
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- 1622 Earth system modeling;
- GLOBAL CHANGE;
- 1804 Catchment;
- HYDROLOGY;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1818 Evapotranspiration;
- HYDROLOGY