poster - International Conference of Agricultural Engineering

4. Conclusions
When comparing the evapotranspiration values estimated by means of the Bowen
Ratio-Energy Balance method (BREB) with the values measured in the lysimeter, in any of
the modalities studied in this paper, it was followed that Bowen method underestimated the
evapotranspiration flux, allowing to detect a process of sensible heat advection, which can be
considered as an important energy source that increases the crop evapotranspiration.
Nevertheless, no greater attention to this phenomenon was paid, since it was out of the
scope of this study. The heat flux advection and its influence when measuring and estimating
evapotranspiration was analysed by Gavilán (2002), who considers that it can contribute up
to 40% of the total energy used in the evapotranspiration process.
A comparison of the hourly values of ET calculated by applying the FAO-56 Penman-
Monteith equation (Allen et al. 1998) with the ones estimated by the BREB method, using
both thermocouples and RTDs for measuring the temperature gradients, proved that both
systems underestimated the evapotranspiration, existing significant differences between both
systems. Even though, the ET values estimated with the BREB method by using RTDs
showed a better adjustment, precision and stability, highlighting a better suitability for
calculating the Bowen ratio.
Acknowledgements
This work has been partially supported by the PPII10-0319-8732 (Ministry of Education
and Science from the Government of Castilla la Mancha) and 08729/PI/08 (Seneca
Foundation) projects.
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