Abstract: Evaporation study in Beijing section of the Yongding River is of great significance to the ecological corridor construction since the Yongding River is recognized as the mother river of Beijing. Several methods are used to calculate water surface evaporation, potential evaporation and actual evaporation in Beijing, China. The research result indicates that water surface evaporation in Beijing is 1182 mm, potential evaporation is 969 mm, and actual evaporation from 1999 to 2009 was 494 mm, while the actual evaporation is 371 mm in the mountainous area, and 425 mm in the plain area when no irrigation is applied. Comparison study is undertaken to the adaptability of the different evaporation method and formula. The Hongjialian formula developed by the Chinese academy of Sciences is applicable to the free water evaporation, and the results of Shichengxi formula and Zaikov formula are close to the measured result. Meanwhile the result by Penman formula is bigger. The cause of which is due to the dynamic part estimate in Penman formula. The correlation analysis and root-mean-square error (RMSE) is used to verify the research results. The average value and RMSE analysis show that the Hongjialian formula is the best way to simulate the water surface evaporation although the correlation analysis shows that the Shichengxi formula is a suitable way. The applicable Potential evaporation method is Presley-Taylor in this study. The results of UN-FAO formula, Hargreves formula, and equilibrium method are not suitable to the result in Beijing. As to the actual evaporation, the Fubaopu method is adapted to the research since it is verified by water balance result. While Zhanglu method and Turc method can be adjusted to each other, but the result of Takahashi Kouichiro is very close to the Fubaopu's result.

Key words: evapotransporation, Fubaopu Formula, Penman Formula, Presley-Taylor Formula, the Yongding River