Tracking Event‐Scale Precipitation Partitioning Reveals Comparable Roles of Event Characteristics and Seasonality in Shaping Precipitation Fate in a Forested Landscape

ABSTRACT The partitioning of precipitation into streamflow ( Q ) and evapotranspiration (ET) is critical for plant water availability, nutrient transport and catchment functioning. Precipitation characteristics and the season in which they occur play a key role in how precipitation is partitioned within a catchment across different time scales. Previous studies have shown that precipitation volume and intensity may shape catchment storm response and storm event water fractions in streamflow, and that precipitation occurring in different seasons can be partitioned differently (e.g., comparing winter vs. summer inputs). In this study, we analysed the effects of precipitation event characteristics and season of occurrence on precipitation partitioning at the event scale on a daily time step using a 1‐year tracking period for each event. This is critical to explore legacy effects of event characteristics on water fluxes over extended timescales and is relevant for understanding catchment‐scale hydrological functioning. We compared the cumulative partitioning fractions of individual events using a forward transit time modelling approach. We integrated hydrometeorological and stable water isotope data with a tracer‐aided transport model based on StorAge Selection (SAS) functions and estimated precipitation partitioning across different event types (mild, moderate, and intense) and seasons in a forested headwater catchment (Wüstebach, Germany). The results showed that summer and spring precipitation returned to the atmosphere more rapidly ( T ≤ 100 days) and in greater proportion than autumn and winter precipitation ( T ≤ 200 days). Mild and intense events, both within and across seasons, showed differences in the magnitude and timing of precipitation partitioning into evapotranspiration, streamflow, and storage during the 1‐year tracking period. Intense autumn precipitation returned to the atmosphere 30% less than mild events. Variations in precipitation partitioning across event types were comparable to those observed across seasons, suggesting that event characteristics play an equally important role as seasonality in determining the fate of precipitation.