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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 20, issue 3
Hydrol. Earth Syst. Sci., 20, 975–990, 2016
https://doi.org/10.5194/hess-20-975-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Hydrol. Earth Syst. Sci., 20, 975–990, 2016
https://doi.org/10.5194/hess-20-975-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 04 Mar 2016

Research article | 04 Mar 2016

The effect of different evapotranspiration methods on portraying soil water dynamics and ET partitioning in a semi-arid environment in Northwest China

Lianyu Yu1,2, Yijian Zeng3, Zhongbo Su3, Huanjie Cai1,2, and Zhen Zheng1,2 Lianyu Yu et al.
  • 1Key Laboratory of Agricultural Soil and Water Engineering in Arid Area of Ministry of Education, Northwest Agriculture and Forestry University, Yangling, China
  • 2Institute of Water Saving Agriculture in Arid Regions of China (IWSA), Northwest Agriculture and Forestry University, Yangling, China
  • 3Faculty of Geo-Information Science and Earth Observation, University of Twente, Enschede, the Netherlands

Abstract. Different methods for assessing evapotranspiration (ET) can significantly affect the performance of land surface models in portraying soil water dynamics and ET partitioning. An accurate understanding of the impact a method has is crucial to determining the effectiveness of an irrigation scheme. Two ET methods are discussed: one is based on reference crop evapotranspiration (ET0) theory, uses leaf area index (LAI) for partitioning into soil evaporation and transpiration, and is denoted as the ETind method; the other is a one-step calculation of actual soil evaporation and potential transpiration by incorporating canopy minimum resistance and actual soil resistance into the Penman–Monteith model, and is denoted as the ETdir method. In this study, a soil water model, considering the coupled transfer of water, vapor, and heat in the soil, was used to investigate how different ET methods could affect the calculation of the soil water dynamics and ET partitioning in a crop field. Results indicate that for two different ET methods this model varied concerning the simulation of soil water content and crop evapotranspiration components, but the simulation of soil temperature agreed well with lysimeter observations, considering aerodynamic and surface resistance terms improved the ETdir method regarding simulating soil evaporation, especially after irrigation. Furthermore, the results of different crop growth scenarios indicate that the uncertainty in LAI played an important role in estimating the relative transpiration and evaporation fraction. The impact of maximum rooting depth and root growth rate on calculating ET components might increase in drying soil. The influence of maximum rooting depth was larger late in the growing season, while the influence of root growth rate dominated early in the growing season.

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The coupled water vapor and heat transport model using two different ET (ETdir, ETind) methods varied concerning the simulation of soil moisture and ET components, while agreed well for the simulation of soil temperature. Considering aerodynamic and surface resistance terms improved the ETdir method regarding simulating soil evaporation, especially after irrigation. The interactive effect of crop growth parameters with changing environment played an important role in estimating ET components.
The coupled water vapor and heat transport model using two different ET (ETdir, ETind) methods...
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