<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Measuring evaporation and transpiration at the field scale is complicated due to the heterogeneity of the environment, with point measurements requiring upscaling and field measurements such as eddy covariance measuring only the evapotranspiration. During the summer of 2014 an eddy covariance device was used to measure the evapotranspiration of a growing maize field at the HOAL catchment. The stable isotope technique and a Lagrangian near field theory (LNF) were then utilized to partition the evapotranspiration into evaporation and transpiration, using the concentration and isotopic ratio of water vapour within the canopy. The stable isotope estimates of the daily averages of the fraction of evapotranspiration (Ft) ranged from 43.0–88.5%, with an average value of 67.5%, while with the LNF method, Ft was found to range from 52.3–91.5% with an average value of 73.5%. Two different parameterizations for the turbulent statistics were used, with both giving similar <italic>R</italic><sup>2</sup> values, 0.65 and 0.63 for the Raupach and Leuning parameterizations, with the Raupach version performing slightly better. The stable isotope method demonstrated itself to be a more robust method, returning larger amounts of useable data, however this is limited by the requirement of much more additional data.</p></abstract>

Measuring evaporation and transpiration at the field scale is complicated due to the heterogeneity of the environment, with point measurements requiring upscaling and field measurements such as eddy covariance measuring only the evapotranspiration. During the summer of 2014 an eddy covariance device was used to measure the evapotranspiration of a growing maize field at the HOAL catchment. The stable isotope technique and a Lagrangian near field theory (LNF) were then utilized to partition the evapotranspiration into evaporation and transpiration, using the concentration and isotopic ratio of water vapour within the canopy. The stable isotope estimates of the daily averages of the fraction of evapotranspiration (Ft) ranged from 43.0–88.5%, with an average value of 67.5%, while with the LNF method, Ft was found to range from 52.3–91.5% with an average value of 73.5%. Two different parameterizations for the turbulent statistics were used, with both giving similar R2 values, 0.65 and 0.63 for the Raupach and Leuning parameterizations, with the Raupach version performing slightly better. The stable isotope method demonstrated itself to be a more robust method, returning larger amounts of useable data, however this is limited by the requirement of much more additional data.

Partitioning evapotranspiration using stable isotopes and Lagrangian dispersion analysis in a small agricultural catchment

Institute of Hydraulic Engineering and Water Resources Management

Institute for Land and Water Management Research, Federal Agency for Water Management

Journal of Hydrology and Hydromechanics

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Measuring evaporation and transpiration at the field scale is complicated due to the heterogeneity of the environment, with point measurements requiring...

Partitioning evapotranspiration using stable isotopes and Lagrangian dispersion analysis in a small agricultural catchment

Published Online: May 26, 2020

Page range: 134 - 143

Received: Jul 08, 2019

Accepted: Feb 07, 2020

DOI: https://doi.org/10.2478/johh-2020-0009

Keywords
Evapotranspiration partitioning, Stable isotopes, Lagrangian dispersion theory

© 2020 Patrick Hogan et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Partitioning evapotranspiration using stable isotopes and Lagrangian dispersion analysis in a small agricultural catchment

Published Online: May 26, 2020

Page range: 134 - 143

Received: Jul 08, 2019

Accepted: Feb 07, 2020

DOI: https://doi.org/10.2478/johh-2020-0009

KeywordsEvapotranspiration partitioning, Stable isotopes, Lagrangian dispersion theory

© 2020 Patrick Hogan et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
Evapotranspiration partitioning, Stable isotopes, Lagrangian dispersion theory