Modelling evapotranspiration in urban green stormwater infrastructures: Importance of sensitivity analysis and calibration strategies with a hydrological model

Evapotranspiration (ET) is crucial for urban runoff management, the cooling efficiency of green stormwater infrastructure (GSI), and vegetation resilience. This research investigates the ability of a commonly used hydrological ET scheme, implemented in HYDRUS-1D, to accurately replicate ET fluxes within GSI, including green roofs (GRs) and rain gardens (RGs), in the Paris region, France. Application of the Sobol sensitivity analysis method indicates that, vegetation height and stomatal resistance are key elements in Penman-Monteith potential ET calculations, while substrate water retention parameters are essential for actual ET simulations. Soil cover fraction, substrate pressure head during the anaerobic phase, and interception parameter also influence ET. Calibration using extensive datasets (water content, ET, drainage) demonstrates improved model accuracy for GRs with thicker substrates compared to those with thinner substrates and for RG setups. Drainage calibration ensures long-term ET simulation accuracy, while calibration with water content or ET observations is recommended during prolonged dry periods.