Actual evapotranspiration (ET) represents an ecosystem key functional variable, directly related with vegetation properties, particularly in water limited environments. The present study aims to map ET using a surface energy fluxes modelling approach, and explore its relation with topographical and floristic composition features, in an arid watershed of Central Chile. Several topographical and vegetation variables were significantly related to ET, however the most important were altitude, northing, easting, the height of herbaceous plants and tree species richness. The patterns of ET rate of the selected variables were explained by the singular eco-hydrological condition of the watershed. These variables were used in a multivariate linear model which allowed an accurate prediction of daily ET for a spring day corresponding to a critical growing vegetation condition.