Applicability of Different Models of Reference Crops Evapotranspiration in China

Measuring and counting reference crops evapotranspiration (ET₀) accurately is of great importance for water resources evaluation and efficient utilization of agricultural water resources. In order to evaluate the applicability of the six formulas in China, this paper selected eight weather stations. They were Erlianhaote, Jiexiu, Yuncheng and Yichang stations which are on the same longitude but in different climatic conditions, and Tieganlike, Huailai, Jinzhou and Dandong weather stations which are on the same latitude but in different climatic conditions. By taking the daily meteorological data of 1960-2012 as the original data, the paper adopted Penman-Monteith method, Makkink, Penman, Kimberly Penman, Hargreaves-Samani, Priestley Taylor and Irmark-Allen to calculate the daily reference crops evapotranspiration. And the other 6 methods were contrastively analysed by using the Penman-Monteith method proposed by United Nations Food and Agriculture Organization. The results show that in the same longitude and latitude, score sequence of Makkink, Pemman and Kimberly Penman is: humid area>sub-arid areas>sub-humid areas>arid areas. Irmark-Allen's entropy score sequence was subhumid area>sub-arid areas>arid zone>humid area. But in the two cases, the order of Hargreaves- Samani and Priestley Taylor is different. The suitability of Hargreaves-Samani and Priestley Taylor is the best in China, followed by Irmark-Allen and Makkink, but the applicability of Penman and Kimberly Penman is poorer. This paper provides theoretical basis and reference by using different types of the formulas to calculate reference crops evapotranspiration in different regions of China.