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| DOI：10.13522/j.cnki.ggps.2019355 |
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| Pan Materials and the Working Environment Affect Water Evaporation Measurements |
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ZHAO Changlong, LIU Yi, WANG Jintao, DONG Xinliang, LI Yonggang, SUN Hongyong
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1. Center for Agricultural Resources Research, IGDB, CAS, Shijiazhuang 050022, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China; 3. Nandagang Agricultural Science Institute of Hebei Province, Cangzhou 061103, China;4. Agricultural Bureau of Jizhou District, Hebei Province, Hengshui 053200, China
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| Abstract: |
| 【Background】Accurate estimation of water surface evaporation is important to understand water cycle and improve water use efficiency. The widely used evaporator in China is the Φ20 evaporation pan, and the conversion from its measurement to real evaporation from water bodies depends on the working environment and the pan materials.【Objective】The aim of this paper is to investigate the influence of pan materials and working environment on the measured evaporation in order to improve accuracy of the evaporation measured in areas without E-601 or E20 evaporator.【Method】The experiment was conducted in a filed at the Nandagang Agricultural Institute from July to September in 2019. We compared the Φ20 pans made by iron and acrylic by installing them on dryland and floating on the water surface of a pond, respectively. In the meanwhile, we also measured water evaporation from two pans with diameters in 10 cm and 50 cm with water depth in them being 30 mm and 50 respectively. During the experiment, we measured the temperature of the surface water and other meteorological factors, and then calculated the potential evaporation using the modified Penman’s formula.【Result】The evaporation measured from the iron pan was 1.2~1.4 times higher than that measured from the acrylic pan. Depending on the measurement sites, the evaporation measured from the pans on dryland could be up to 1.5 times higher than that measured from the pans floating on the water surface. Environment impacted the measurement more than the pan materials, and the sum of the squared deviation due to environmental impact was 131.59, approximately threefold that of the pan materials. The fitting between the potential evaporation and the evaporation measured from the floated Φ20 iron pan was good, and the water surface evaporation was correlated with vapor pressure deficit, water surface temperature and duration of sunshine.【Conclusion】The environmental factors such as saturated vapor pressure deficit and water surface temperature were the major determinants of water surface evaporation in the studied area. The location of the pan also affected the measurement accuracy. The evaporation measured from the pan on dryland was much higher than that measured from the pan floating on the water surface. The pan size and initial water depth in it did not impact the measurement at significant level. For the pan installed on the dryland, making it with low thermal-conductive materials was more accurate, while for the floating pan making it with high thermal-conductive materials worked better. |
| Key words: evaporators; pan materials; environment; water surface evaporation; meteorological factors |
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