Application of a multi-cylinder evapotranspirometer method for evapotranspiration measurements in wetlands

Abstract

This paper introduces a multi-cylinder evapotranspirometer method, which can directly measure evapotranspiration (ET) from emergent plants in different species and states as well as simultaneously measure evaporation ( E W) from an open water surface. Values of daily ET from three contrasting reed ( Phragmites australis) stands, with different leaf area indexes (LAI), were obtained through in situ measurements of the Baiyangdian wetland using this method during the growing seasons in 2008 and 2009. The results showed that the ET rate of the reed belt was very high, even exceeding 20 mm d −1 under extreme weather conditions. Depending on the LAI change, the annual ET from the different reed canopies ranged from 970 to 2035 mm, whereas the ET/ E W ratios ranged from 2.05 to 3.98. Accuracy analysis results showed that the errors of the measurement from this method were no more than 2 mm. The relative errors of the measurement were correspondingly from 0.04% to 0.33%. It is indicated that the accuracy of our measurement is good enough for the requirements of the ET measurement.