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| DOI：10.13522/j.cnki.ggps.20180572 |
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| Change in ET0 and the Model to Estimate it: A Case Study for Xinxiang |
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ZHANG Yanbo
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Xinxiang Hydrology and Water Resources Survey Bureau, Xinxiang 453000, China
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| Abstract: |
| 【Objective】 Reference crop evapotranspiration (ET0) is an important parameter in many hydrological and ecological processes. It is also needed in irrigation management. This paper presents a method to estimate the change in ET0 based on data measured from a weather station in Xinxiang, Henan province. 【Method】 We calculated annual and seasonal ET0 using the Penman-Monteith formula based on meteorological data measured from 1962 to 2016 at a meteorological station in Xinxiang. The Mann-Kendall test and mean generating function model were used to analyze any possible trend in the ET0 at both annual and seasonal scales. 【Result】① Annual ET0 was in decline from 1975 to 2016, especially from 1985 to 2004 and in 2006. ②Spring ET0 was in decline from 1982 to 1983 and from 1988 to 2003, and summer ET0 dropped from 1980 to 2012. ③The mean generating function model fitted the annual ET0 well, with a consistency coefficient of 0.83, and absolute and relative error of -120.8～120.0 mm and -14.0%～18.2%, respectively. ④The consistency coefficient of fitting the mean generating function model to the seasonal ET0 was 0.85, 0.81, 0.88 and 0.89 for spring, summer, autumn and winter respectively, the associated absolute error was -60.2～64.3 mm, -64.4～58.9 mm, -39.6～32.8 mm and -37.0～25.1 mm, and the associated relative error was -20.1%～36.7%, -22.1%～32.1%, -18.0%～22.9% and -23.9%～24.6%, respectively.【Conclusion】The annual ET0 in Xinxiang area had been in decline from 1985 to 2004, due to its decrease in spring and summer. The mean generating function model can fit both annual and seasonal ET0, and can thus be used to estimate the annual and seasonal ET0. The fitting of the mean generating function model to the autumn and winter ET0 was better than fitting to the spring and summer ET0. |
| Key words: reference crop evapotranspiration; Xinxiang area; Mann-Kendall test; mean generation function model |
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