Validating remote sensing derived evapotranspiration with the soil and water assessment tool (SWAT) model: A case study in Zhelin Basin, China

Evapotranspiration (ET) is a major component in the water and heat balance of terrestrial ecosystems as well as in the water, energy and carbon cycles on the Earth’s surface. A growing number of studies have focused on the retrieval of ET from remote sensing (RS) data. However, the RS-derived ET results could not be validated by station-observed data directly for the difference of the scale. The objective of this study is to present an operational approach to validation of RS-derived ET under the support of a distributed hydrological model: soil and water assessment tool (SWAT). Five years (2000-2004) evapotranspiration data of Zhelin Basin, the study area, were prepared. RS-derived ET and other data (DEM, land-use data, soil data, etc) were processed together in SWAT to simulate the hydrological cycle. The output monthly runoff is compared with observed runoff data. The RS-derived ET was then validated based on the results of those comparison (R 2 =0.8516, RMSE=26.0860, MBE=-8.6578). It indicated that the method presented in the paper was an operational and feasible way for validation of ET data from remote sensing retrieval.