Remote sensing study of evapotranspiration in the Heihe River Basin, Northwest of China

As an important component in hydrological cycle and a main part of energy balance, evapotranspiration (ET) in Heihe River Basin in northwest of China was studied with remotely sensed data. In this paper, we use NOAA AVHRR data and selected Priestley-Taylor equation as model to estimate ET. A new method to determine alpha by using vegetation indices and differences between air temperature and land surface temperature was proposed. ET and many biophysical parameters were validated with relative data of HEIFE Experiment, and the results showed that the remote sensing estimations of ET and surface parameters are accord with land surface measurements. The spatial and temporal distribution of LE was studied. The results are as follows: the LE is whenever very low in the cold desert, desert and gobi. In the Ruoshui delta and Gurinai lake basin covered by well vegetation, LE differs from their around areas. In middle reaches, LE of artificial oasis changes with the crop growth stage. LE of the natural oasis nearby the rivers differs from that of the around desert and gobi because of the different water resource conditions. High degree overlay grassland and marshes have the highest LE in Heihe river basin