| Reference crop evapotranspiration (ET0) is the base for calculating crop water requirements, and it generally uses the Penman-Monteith Formula (PM formula) recommended by FAO to calculate. But this method cannot be used in some regions in Hetao irrigation district, due to lack of the measured radiation data. Herein in this paper, we selected and used the dail
y climatic data at Linhe Meteorological Station from 1990 to 2012, analyzed the relation between the reference crop evapotranspiration (ET0) estimated by the PM formula to the climatic factors, has found the net radiation that was the dominated factor greatly influencing ET0, the second factors were the saturated vapor pressure deficit and mean temperature. Also has established the ET0 estimating formula based on the saturated vapor pressure deficit, temperature and wind speed. By the confirmation, the correlation coefficient, Nash Efficiency Coefficient and overall equilibrium coefficient were 0.96, 0.92 and 1.00, respectively. Under the condition of lack the measured wind speed, another estimated ET0 formula by considering the saturated vapor press deficit and temperature was established. These two formulas can be provided the simple and accurate methods for estimating ET0 in Hetao irrigation district when the measured meteorological data was limited. |