This study investigated the temporal evolution of baseflow and other runoff components during two consecutive rainfall events occurring at a two-day interval. End-Member Mixing Analysis (EMMA) was employed to assess the impact of antecedent rainfall on the subsequent event, alongside the characterization of hydrograph components. Environmental tracers, specifically stable isotopes (δ¹⁸O and δD) and dissolved silica (Si), were utilized to trace water origins and subsurface processes. Due to measurement limitations, the maximum silica concentration in the soil water component was estimated via a mass balance-based trial-and-error approach, which warrants further empirical validation. Hydrograph separation was performed using both 3-component (Event 1, Event 2, and baseflow) and 4-component (incorporating soil water) mixing models. The 4-component model provided a more physically plausible interpretation of baseflow dynamics; while the 3-component model attributed over 50% of the discharge to baseflow, the 4-component model revealed soil water as the dominant contributor. Furthermore, the results suggest that Event 1, which was 4.5 times larger than the subsequent event, had a persistent impact on streamflow during and beyond the second rainfall. This study confirms that streamflow is more significantly influenced by pre-event water (baseflow and soil water) than by direct event. The higher contribution of soil water relative to baseflow is attributed to the distinct hydraulic differences between fast-flow (soil water) and slow-flow (baseflow) regimes.

Keywords: Baseflow, Environmental Tracer, End-Member Mixing Analysis, Mass balance, slow-flow