Adaptability Research of Different Reference Crop Evapotranspiration Estimated Methods in Shaanxi

LIAO Xian-qin; LI Yi

Abstract：It is the foundation of crop water requirement and production management to make the accurate estimation of reference crop evapotranspiration (ET_0) for every region,particularly,it is very important for agricultural water-saving irrigation planning.The daily ET_0 was computed by five methods with the meteorological data from six weather stations of Shaanxi.As FAO56 Penman-Monteith (P-M) method is taken as the standard,the comparison is taken and the results are as follows.The variation trend of ET_0 calculated by five methods is roughly the same for six stations in Shaanxi,but the value are different,and all differences increase along with the increase of ET_0.The difference of the results computed by Hargreaves method is so small,and it is adaptable for every region.1948Penman and Priestley-Taylor are better methods for every climatic area than FAO24 Penman.If climatic data are insufficient,Priestley-Taylor method for any region may provide reliable ET_0 estimation.A better result also can been obtained by FAO24 Penman method,but the precision of its estimated results is lower than Priestley-Taylor method,and it is not used generally.Meanwhile the relationship between the ET_v alue computed by P-M method and evaporation is analyzed and that can provide a reference for estimating ET_0 using evaporation data for six stations in Shaanxi region.