Modifying Hargreaves model considering radiation to calculate reference crop evapotranspiration in hilly area of central Sichuan Basin

作者：Jia Yue; Cui Ningbo^*; Wei Xinping; Gong Daozhi; Hu Xiaotao

来源：Transactions of the Chinese Society of Agricultural Engineering, 2016, 32(21): 152-160.

DOI：10.11975/j.issn.1002-6819.2016.21.020

• Applicability evaluation
• Average absolute error
• Central Sichuan Basin
• Food and agriculture organizations
• Hargreaves
• Meteorological station
• Reference crop evapotranspirations
• The Bias principle

Reference crop evapotranspiration (ET0) is an important parameter in water cycle and water balance. Accurate estimation of ET0becomes vital in planning and optimizing irrigation schedules and irrigation system management. Numerous methods have been proposed for estimating ET0, among which the Penman-Monteith (P-M) method recommended by Food and Agriculture Organization of the United Nations (FAO) in 1998 provides the most accurate results across the world wherever in arid or humid environment. But the main problems when computing ET0by the P-M method are its complicated nonlinear process and requirements of many climatic variables. Thus, there is an urgent need to develop a much simpler and more appropriate method in areas with limited data, such as the Hargreaves-Samani (H-S) method. In order to improve the ET0calculation accuracy of the H-S method, in this research the daily data of 13 representative meteorological stations from 1954 to 2013 in hilly area of central Sichuan was used to calculate the ET0. The H-S method was modified based on the Bayesian principle and the impact of the radiation, and at the same time the accuracy of the modified method was evaluated. The result showed that in ZoneI the parameter a was 0.915, in Zone II was 0.922, in Zone III was 0.912, and the parameter b was the function of radiation. The trend of the modified method's computing result was similar to the P-M method and both showed a parabolic shape. Compared with the H-S method, the average absolute error of ten-day ET0with the modified H-S method decreased from 0.93 to 0.15 mm/d in Zone I, from 0.95 to 0.19 mm/d in Zone II and from 0.93 to 0.28 mm/d in Zone III. The fitting equation slope of ten-day ET0was 0.89, 0.94 and 0.90 respectively in these areas using the modified method, and the calculation accuracy was enhanced remarkably. During the period between March and October, the average absolute error of monthly ET0decreased from 0.89 to 0.46 mm/d in Zone I, from 1.14 to 0.29 mm/d in ZoneII and from 1.28 to 0.21 mm/d in Zone III, respectively. In January, February and December, the average absolute error of monthly ET0changed from 0.14 to 0.35 mm/d in ZoneI, decreased from 0.31 to 0.30 mm/d in Zone II and from 0.32 to 0.28 mm/d in Zone III. The fitting equation slope of monthly ET0was 0.83, 0.89 and 0.90 respectively in these areas using the modified method. The accuracy of modified method decreased when the altitude increased. In the whole year, the accuracy increased by 47%, the accuracy in Zone I increased by 35% and the accuracy in Zone II increased by 48% especially in the main crop growth period. Therefore, the modified H-S method based on the Bayesian theory is more adaptive and accurate, and can be used as a simple method for the calculation of ET0in hilly area of central Sichuan Basin.

• 出版日期2016
• 单位四川大学