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

► There are many types of emergent macrophytes with complicated distributions in wetland environments. However, previously used analysis methods cannot reflect the differences of evapotranspiration (ET) among diverse types of plants. In this study, we introduce a multi-cylinder evapotranspirometer method, which can directly measure ET from emergent plants in different species and states as well as simultaneously measure evaporation (EW) from an open water surface. ► There are inherent differences in the ET rates for reed (Phragmites australis) stands with different leaf area indexes (LAI). To investigate the water cycle process of wetland accurately, values of daily ET from three contrasting reed stands were obtained through in situ measurements in Baiyangdian wetland using the multi-cylinder evapotranspirometer during the growing seasons in 2008 and 2009. The results showed that the annual ET from the different reed canopies ranged from 970 to 2035mm depending on the LAI change. ► Before applying in situ, the measuring accuracy of the multi-cylinder evapotranspirometer method has been evaluated in laboratory. Accuracy analysis results showed that 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. 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.