Study on the Estimation and Dynamic Changes of Evapotranspiration in Huangfuchuan Watershed

Using remote sensing approach for retrieval of large area evapotranspiration has important guidance for effective utilization of water resources.The Huangfuchuan watershed located in Ordos Plateau which has been intensively studied in the past was taken as the study area.Remote sensing approach was used to retrieve instantaneous evapotranspiration based on the estimation of land surface characteristics and fluxes from Landsat-5 TM images collected in 1996,2003,and 2007,and using auxiliary environmental data from the same time periods.Daily evapotranspiration was estimated by scaling.The result of evapotranspiration distribution was consistent with land surface conditions.The daily evapotranspiration of area covered by vegetation was higher than bare land.The daily evapotranspiration of dense vegetation was higher than the sparse.The daily evapotranspiration in sunny slope was higher than that in shady slope.The maximum daily evapotranspiration was water body and the minimum one was bareland.Results for 1996 and 2007 were verified by using measured data and the FAO method.This level of uncertainty was acceptable;therefore,the method was applicable.These three images were compared and evapotranspiration decreased from 1996 to 2003 and 2007.