Estimating Daily Evapotranspiration in Guanchuanhe River Basin Using Remote Sensing

The method used in the study is based on surface energy balance equation, i.e. Rn =lambdaET + H + G. By analyzing the spatial distribution of ET, we can draw that the spatial variation of ET is obvious. The estimated ET value ranges from 1.2 to 8.5 mm, with the average value of 4.7 mm on April 15, 2000. Spatially, it increased from north to south. The highest value is occurred at the source of the river, where is woodland distributing. The results have been validated by field data, and the root mean square error (RMSE) is 0.8. The errors are less than 0.7 mm in most of the stations except one. It proved that the method is feasible to estimate ET in the study area. The study enables us to better predict land surface hydrological cycle and lays a foundation for ecological restoration and application of distributed hydrologic model.