Soil moisture and precipitation intensity jointly control the transit time distribution of quick flow in a flashy headwater catchment

作者：Hatice Türk, Christine Stumpp, Markus Hrachowitz, Karsten Schulz, Peter Strauß, Günter Blöschl, Michael Stockinger · 发表于：Hydrology and earth system sciences · 年份：2025 · DOI：10.5194/hess-29-3935-2025 · 被引用次数：4 · 研究领域：Hydrology and Watershed Management Studies、Soil Moisture and Remote Sensing、Soil and Unsaturated Flow

Abstract. The rainfall–runoff transformation in catchments usually follows a variety of slower and faster flow paths, leading to a mixture of “younger” and “older” water in streamflow. Previous studies have investigated the time-variable distribution of water ages in streamflow (transit time distribution, TTD) using stable isotopes of water (δ18O, δ2H) together with transport models based on StorAge Selection (SAS) functions. These functions are traditionally formulated based on soil moisture to mimic the preferential release of younger water as the system becomes wetter. In this study, we hypothesized that, in a heterogeneous catchment with a significant fast-runoff response component, precipitation intensity, in addition to soil moisture, plays a critical role in the preferential release of younger water. To test this hypothesis, we used high-resolution δ18O data (weekly and event-based streamflow δ18O samples) in a 66 ha agricultural catchment. We tested two scenarios of the SAS function parameterization for the preferential-flow age selection: one as a function of soil moisture only and one as a function of both soil moisture and precipitation intensity. The results showed that accounting for both soil moisture and precipitation intensity to define the shape of SAS functions for preferential flow improved the tracer simulation in streamflow (increasing the Nash–Sutcliffe efficiency from 0.31 to 0.51). This also led to a higher percentage of streamflow (an increase from 2....