Assessment of the green roof retention capacity: the role of the evapotranspiration

Evapotranspiration (ET) is a keystone that affects the hydrological performance of green infrastructures since ET is the hydrological process responsible for the restoring of water holding capacity of green infrastructures. Taking into account the needs to effectively estimate the impact of green infrastructures on the hydrological response at the urban catchment scale, particular attention has recently been given on the estimation of the actual ET in continuous simulations. In this framework, the main objective of this paper is to assess the role of the actual ET in restoring the water holding capacity of green roofs in the Mediterranean climate. In particular, the analysis is supported by 19 months continuous monitoring of the soil water content of the green roof experimental site, located in Genoa (IT). The study illustrates a water balance model and a simple procedure to estimate correction factors based on the analysis of monitored dry weather periods; results confirm the suitability of the proposed model in describing the moisture losses in the dry period however the specific correction factor (Ks) is needed to properly measure the actual evapotranspiration rates.