Evapotranspiration is a key component of the hydrological cycle, influencing water and biogeochemical cycles in the critical zone. Particularly, the travel time of evapotranspired water is critical for describing the origin and young water contribution to evapotranspiration, but is yet poorly understood. In this study, we revisited the Lagrangian particle-tracking model, EcoSLIM, to separate evaporation and transpiration particles using a mass balance approach. This separation allowed us to determine the travel time distribution of particles with different sources (i.e., rainfall, snowmelt, and pre-stored groundwater) captured by evaporation and transpiration. We validated the mass of evapotranspiration, evaporation and transpiration particles against those computed by the physically-based ParFlow-CLM model, which yields the expected mass of target fluxes by simulating the physical processes controlling water and energy balances. Our results demonstrated the high accuracy of the modified EcoSLIM in closing the mass balance, as evidenced by R