Impacts of climatological variability on Evapotranspiration: A Sensitivity Analysis for Urban Drainage Applications

Understanding the sensitivity of reference evapotranspiration (ET0) to meteorological variables is critical for improving urban water management and climate adaptation strategies. This study analyses the one-way and two-way sensitivity of ET0 to maximum temperature (Tmax), wind speed (u2), net solar radiation (Rn), and maximum relative humidity (RHmax) using the FAO-56 Penman-Monteith equation for multiple meteorological stations in Paris area. One-way sensitivity analysis revealed that Tmax and Rn have the strongest influence on ET0 in summer, while wind speed and RHmax show secondary but notable effects, particularly in winter and transitional seasons. A two-way sensitivity analysis was conducted for Tmax and RHmax, considering their joint influence on vapor pressure deficit (VPD). The results indicate a nonlinear relationship, where higher Tmax and lower RHmax significantly increase VPD, amplifying ET0, while increasing RHmax dampens this effect. Seasonal variations highlight stronger ET0 sensitivity in summer and reduced impact of Rn in winter due to high humidity levels. Windspeed has its major role in shaping evapotranspiration in winter and in dense urban settings. These findings emphasize the need for climate-adaptive urban drainage models, integrating ET0 variability to enhance stormwater retention, flood resilience, and green infrastructure efficiency under changing climate conditions. Future research should refine ET0 modelling for urban microclimates, ensuring accurate water balance predictions in cities

Impacts des épisodes orageux importants: comment prendre en compte la variabilité temporelle des rejets non traités dans un système d'assainissement urbain?

International audienceIn typical life cycle impact assessment (LCIA) studies of urban wastewater systems (UWS), average conditions are modelled but there are many annual flooding events with releases of untreated sewage. Such peak conditions are not considered and present a high temporal variability which is not currently accounted for. In addition, the aggregation of the loads from several storm events could bring an issue for the impact assessment on the aquatic categories of eutrophication and ecotoxicity. Hence we are investigating the contributions of these wet weather-induced discharges along with the inclusion of temporal variability in the life cycle inventory (LCI) for UWS. In the framework of the OPUR research programme (Observatory of Urban Pollutants) and in collaboration with the Paris public sanitation service (SIAAP), this work aimed at identifying and describing contributing flows from the UWS in the Paris area by a selection of routine wastewater parameters and priority pollutants. This collected data is organized according to archetypical weather days over a 24-hr span. Secondly, for each archetypical weather days and its associated flows to the receiving river water (Seine) the parameters of pollutant loads (statistical distribution of concentrations and volumes) are determined with statistical treatment of data. Then, the inventory flows (i.e. the potential loads from the UWS) can be used as inputs in a classical LCA to investigate the relative importance of episodic wet weather versus "continuous" dry weather loads coupled to further uncertainty analysis using a Monte Carlo method. Results analysis showed that a few severe events can be important contributors to the total annual pollutant load on some parameters (routine wastewater pollutants but also priority pollutants). The proposed method based on the definition and characterization of archetypical weather days has shown the appropriate level of temporal differentiation in the LCI to assess the impacts from unmanaged pollutant loads from UWS during intense storm events. With such significant contributions of pollutant loads at the LCIA level, further research is required to include temporally-differentiated emissions in the methodological framework of the aquatic categories of eutrophication and ecotoxicity, to better understand how the performance of an UWS system affects the receiving environment for given local weather conditions

Impacts des épisodes orageux importants: comment prendre en compte la variabilité temporelle des rejets non traités dans un système d'assainissement urbain?

International audienceIn typical life cycle impact assessment (LCIA) studies of urban wastewater systems (UWS), average conditions are modelled but there are many annual flooding events with releases of untreated sewage. Such peak conditions are not considered and present a high temporal variability which is not currently accounted for. In addition, the aggregation of the loads from several storm events could bring an issue for the impact assessment on the aquatic categories of eutrophication and ecotoxicity. Hence we are investigating the contributions of these wet weather-induced discharges along with the inclusion of temporal variability in the life cycle inventory (LCI) for UWS. In the framework of the OPUR research programme (Observatory of Urban Pollutants) and in collaboration with the Paris public sanitation service (SIAAP), this work aimed at identifying and describing contributing flows from the UWS in the Paris area by a selection of routine wastewater parameters and priority pollutants. This collected data is organized according to archetypical weather days over a 24-hr span. Secondly, for each archetypical weather days and its associated flows to the receiving river water (Seine) the parameters of pollutant loads (statistical distribution of concentrations and volumes) are determined with statistical treatment of data. Then, the inventory flows (i.e. the potential loads from the UWS) can be used as inputs in a classical LCA to investigate the relative importance of episodic wet weather versus "continuous" dry weather loads coupled to further uncertainty analysis using a Monte Carlo method. Results analysis showed that a few severe events can be important contributors to the total annual pollutant load on some parameters (routine wastewater pollutants but also priority pollutants). The proposed method based on the definition and characterization of archetypical weather days has shown the appropriate level of temporal differentiation in the LCI to assess the impacts from unmanaged pollutant loads from UWS during intense storm events. With such significant contributions of pollutant loads at the LCIA level, further research is required to include temporally-differentiated emissions in the methodological framework of the aquatic categories of eutrophication and ecotoxicity, to better understand how the performance of an UWS system affects the receiving environment for given local weather conditions