<abstract xmlns="http://www.w3.org/1999/xhtml">Employing evapotranspiration models is a widely used method to estimate reference evapotranspiration (ETREF) based on weather data. Evaluating such models considering site-specific boundary conditions is recommended to interpret ETREF-calculations in a realistic and substantiated manner. Therefore, we evaluated the ASCE standardized ETREF-equations at a subhumid site in northeastern Austria. We calculated ETREF-values for hourly and daily time steps, whereof the former were processed to sum-of-hourly values. The obtained data were compared to each other and to ET-values measured by a weighing lysimeter under reference conditions. The resulting datasets covered daily data of the years 2004 to 2011.Sum-of-hourly values correlated well (r2 = 0.978) with daily values, but an RMSE of 0.27 mm specified the differences between the calculation procedures. Comparing the calculations to lysimeter measurements revealed overestimation of small ETREF-values and underestimation of large values. The sum-of-hourly values outperformed the daily values, as r2 of the former was slightly larger and RMSE was slightly smaller. Hence, sum-of-hourly computations delivered the best estimation of ETREF for a single day. Seasonal effects were obvious, with computations and measurements being closest to each other in the summer months.</abstract>

Employing evapotranspiration models is a widely used method to estimate reference evapotranspiration (ETREF) based on weather data. Evaluating such models considering site-specific boundary conditions is recommended to interpret ETREF-calculations in a realistic and substantiated manner. Therefore, we evaluated the ASCE standardized ETREF-equations at a subhumid site in northeastern Austria. We calculated ETREF-values for hourly and daily time steps, whereof the former were processed to sum-of-hourly values. The obtained data were compared to each other and to ET-values measured by a weighing lysimeter under reference conditions. The resulting datasets covered daily data of the years 2004 to 2011.Sum-of-hourly values correlated well (r2 = 0.978) with daily values, but an RMSE of 0.27 mm specified the differences between the calculation procedures. Comparing the calculations to lysimeter measurements revealed overestimation of small ETREF-values and underestimation of large values. The sum-of-hourly values outperformed the daily values, as r2 of the former was slightly larger and RMSE was slightly smaller. Hence, sum-of-hourly computations delivered the best estimation of ETREF for a single day. Seasonal effects were obvious, with computations and measurements being closest to each other in the summer months.

Evaluation and validation of the ASCE standardized reference evapotranspiration equations for a subhumid site in northeastern Austria

Institute of Hydraulics and Rural Water Management; Department of Water, Atmosphere and Environment

University of Natural Resources and Life Sciences

Institute of Hydrology, Slovak Academy of Sciences

Journal of Hydrology and Hydromechanics

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

Employing evapotranspiration models is a widely used method to estimate reference evapotranspiration (ETREF) based on weather data. Evaluating such models...

Evaluation and validation of the ASCE standardized reference evapotranspiration equations for a subhumid site in northeastern Austria

Published Online: Jun 26, 2019

Page range: 289 - 296

Received: Jan 08, 2018

Accepted: Oct 30, 2018

DOI: https://doi.org/10.2478/johh-2019-0004

Keywords
Weighing lysimeter, Calculations, Hourly, Sum-of-hourly, Daily time steps

© 2019 Reinhard Nolz et al., published by Sciendo

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

Evaluation and validation of the ASCE standardized reference evapotranspiration equations for a subhumid site in northeastern Austria

Published Online: Jun 26, 2019

Page range: 289 - 296

Received: Jan 08, 2018

Accepted: Oct 30, 2018

DOI: https://doi.org/10.2478/johh-2019-0004

KeywordsWeighing lysimeter, Calculations, Hourly, Sum-of-hourly, Daily time steps

© 2019 Reinhard Nolz et al., published by Sciendo

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

Keywords
Weighing lysimeter, Calculations, Hourly, Sum-of-hourly, Daily time steps