Sensitivity of stable isotope dynamics to parametric and conceptual choices in critical zone hydrological modelling : a case study in Tropical Africa Chávez-Espinoza, D. /Kuppel, Sylvain /Peugeot, Christophe Yoshimura, K. Vallet-Coulomb, C. EcH2O-iso evaporative kinetic fractionation isotope-enabled ecohydrological modelling sensitivity analysis tropical hydrology water stable isotopes Tracer-enabled hydrological models are increasingly used to investigate water pathways by integrating hydrometric and stable isotope data. While quantifying the sensitivity of model outputs to global parameters is a common practice, structural sensitivity to empirical evaporative fractionation models is rarely explored, despite its critical influence on isotopic signatures, especially in evapotranspiration-dominated basins. In this study, we build upon the process-based distributed model EcH2O-iso to quantify both types of isotopic sensitivities-conceptual, from changing the Craig and Gordon formulation used to quantify soil evaporative fractionation, widely applied in tracer-enabled hydrology, and parametric, from varying classical non-isotopic hydrodynamics parameters-in a tropical savanna basin in northern Benin with mixed land cover (fallow and forest). Looking at five locations and hydrological compartments, covering both local and basin scales, our results show that both types of sensitivities are of similar magnitude and significance, leading to changes in delta 18O outputs by several per mil. We further show that the choice of conceptual fractionation framework influences parametric sensitivities, especially locally, while at basin scales, sensitivities decrease as mixing may dominate over fractionation processes. Additionally, we highlight how vegetation-dependent root uptake further modulates the impact of modelling choices on tracer sensitivity. The differentiated relationships between inputs (parametric and conceptual) and outputs (isotopic time series) not only demonstrate the leverage of isotopic information to identify model configurations but also benchmark how evaporation fractionation formulations may alter the propagation of this information for estimating parameters controlling water storage and fluxes. 2025 text https://www.documentation.ird.fr/hor/fdi:010095795 fdi:010095795 Chávez-Espinoza D., Kuppel Sylvain, Peugeot Christophe, Yoshimura K., Vallet-Coulomb C.. Sensitivity of stable isotope dynamics to parametric and conceptual choices in critical zone hydrological modelling : a case study in Tropical Africa. 2025, 39 (11), e70337 [19 p.] EN BENIN AFRIQUE ZONE TROPICALE