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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2016-252
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
15 Jun 2016
Review status
A revision of this discussion paper was accepted for the journal Hydrology and Earth System Sciences (HESS) and is expected to appear here in due course.
A site-level comparison of lysimeter and eddy-covariance flux measurements of evapotranspiration
Martin Hirschi1, Dominik Michel1, Irene Lehner1,2, and Sonia I. Seneviratne1 1Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, 8092 Zürich, Switzerland
2Present address: Centre for Environmental and Climate Research (CEC), University of Lund, Lund, Sweden
Abstract. Accurate measurements of evapotranspiration are required for many meteorological, climatological, ecological, and hydrological research applications and developments. Here we examine and compare two well-established methods to determine evapotranspiration at the site level: lysimeter-based measurements (EL) and eddy-covariance (EC) flux measurements (EEC). The analyses are based on parallel measurements carried out with these two methods at the research catchment Rietholzbach in northeastern Switzerland, and cover the time period June 2009 to December 2015. The measurements are compared on various time scales, and with respect to a 40-year lysimeter-based evapotranspiration time series. Overall, the lysimeter and EC measurements agree well, especially on the annual time scale. On that time scale, the long-term lysimeter measurements also correspond well with catchment water-balance estimates of evapotranspiration. This highlights the representativeness of the site-level lysimeter and EC measurements for the entire catchment despite their comparatively small source areas and the heterogeneous land use and topography within the catchment. Furthermore, we identify that lack of reliable EC measurements during and following rainfall events (due to limitations of the measurement technique under these conditions) significantly contributes to an underestimation of EEC and to the overall energy balance gap at the site.

Citation: Hirschi, M., Michel, D., Lehner, I., and Seneviratne, S. I.: A site-level comparison of lysimeter and eddy-covariance flux measurements of evapotranspiration, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-252, in review, 2016.
Martin Hirschi et al.
Martin Hirschi et al.

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Short summary
We compare lysimeter and eddy-covariance (EC) flux measurements of evapotranspiration at a research catchment in Switzerland. The measurements are compared on various time scales, and with respect to a 40-year long-term lysimeter time series. Overall, the lysimeter and EC measurements agree well, especially on the annual time scale. Furthermore, we identify that lack of reliable EC data during/after rainfall events significantly contributes to an underestimation of EC evapotranspiration.
We compare lysimeter and eddy-covariance (EC) flux measurements of evapotranspiration at a...
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