A distributed model of reference evapotranspiration based on the DEM

A distributed model for regional reference evapotranspiration was developed and applied for the daily simulation of evapotranspiration on August 28,2000 in Ordos sandland basin of the Kaokaolaigou river(area 114 km²).In the distributed evapotranspiration model,the radiation and vapour pressure strongly related to topography were adjusted firstly by utilizing GIS spatial analysis,then the spatial distribution of reference evapotranspiration was calculated and analyzed.Among the parameters,the temperature and wind speed were considered uniformity within the basin because of small variations in them.The result shows that the spatial variation of reference evapotranspiration is obvious because the radiation is depended highly on slope and aspect.The variation of reference evapotranspiration is increased with the enhancing spatial resolution of the model.The model is helpful for improving estimation of regional evapotranspiration,regional water balance study and distributed geographical model study and combating desertification.