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Measuring and modelling evapotranspiration from Douglas-fir stands

University of British Columbia

Methods of measuring forest evapotranspiration are reviewed and evaluated. Measurements on Douglas-fir stands indicated that eddy correlation, Bowen ratio/energy balance, stomatal diffusion resistance and soil water balance methods agreed with each other to within their respective measurement errors. A detailed error analysis of a Bowen ratio/energy balance system indicated that it could give estimates of evapotranspiration to within ± 15% and ± 40% when evapotranspiration was high and low, respectively. The accuracy of this system was due to the use of a high sensitivity monitoring system, and the periodic reversal of well-matched sensors which results in the cancelling of certain systematic errors. The effects of certain non-cancelling errors are also illustrated. Approaches to modelling forest evapotranspiration are reviewed and two approaches chosen for further study. Data obtained using the Bowen ratio/energy balance, stomatal diffusion resistance and soil water balance methods are used in the development and testing of two forest evapotranspiration models. These models are combined with simple interception and drainage relationships to produce two forest water balance models. [the rest of the abstract can be found in the attached PDF file]

Text

2010-03-31

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http://hdl.handle.net/2429/23182

Soil Science

University of British Columbia

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