estimation of evapotranspiration using satellite image data in mashhad area

abstract evapotranspiration (et) determination is a key factor for irrigation scheduling, water balance, irrigation system design and management and crop yields simulation. therefore many scientists have tried to estimate evapotranspiration in different spatial and temporal scales. remote sensing is a one of new technique in estimation of et in regional scales. so, in this study it’s tried to estimate spatial distribution daily actual et for mashhad’s sub basin using modis image data related to 4th june, 1st july and 26th july 2009 and surface energy balance algorithm for land (sebal) taking into account topographic effects. the results showed that modis image data and sebal method were able to estimate actual daily et in mashhad sub-basin properly. based on the results, areas which had dense vegetation and low temperatures had high et rates, while in areas with sparse vegetation and high temperatures the et rate was low.