The problem of the increase in the magnitude and frequency of flooding events in urban areas can be approached by means of techniques of sustainable urban stormwater management such as the green roofs (GRs). In this study, the effectiveness of this green infrastructure has been investigated. For this purpose, a daily scale hydrological model for GRs based on water balance equations, has been proposed. Evapotranspiration (ET) is a key process of the water balance of a GR. In light of this, in the present work, a study of the dynamics involved in ET process has been carried out. To this aim micro-meteorological and eddycovariance (EC) data at the Rollesbroich experimental site have been analyzed from July 2013 to June 2015