Pyschik, J.; Kuleshov, A.; Fasching, C.; Chifflard, P.; Hopp, L.; Blume, T. & Weiler, M. (2025): <b>A comparative study of subsurface stormflow at three trenched hillslopes: sources, pathways and tracer behavior (preprint)</b>. <i>Water Resource Research</i> <b>...</b>(...), ...
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Title:
A comparative study of subsurface stormflow at three trenched hillslopes: sources, pathways and tracer behavior (preprint)
Subsurface stormflow (SSF) is a key runoff generation mechanism in small catchments, yet its dynamics and thresholds remain poorly understood due to the challenges of observing and measuring subsurface processes. To address this, we conducted a study in a headwater catchment in the Black Forest, Germany, where we investigated the depth of SSF flow paths, if SSF is dominated by event water and if all SSF events have similar tracer behavior. Three trenches were installed on slopes with different landuse and topography. They were excavated down to bedrock ( 15 m wide, 2.5 m deep), collecting SSF separately from upper and lower soil layers. Continuous measurements of SSF volume and temperature were combined with water sampling for natural tracers: stable water isotopes, dissolved organic carbon, electric conductivity, and major ions. During the study period, 6 large SSF events were recorded in each trench. Using heat as a tracer we found stable SSF flowpath depths across events. Multitracer analysis suggested that SSF consisted mostly of pre-event water, with antecedent wetness governing event water contributions. Our results also show that C–Q relationships for solutes varied considerably between events and trenches, with some (e.g., Si) remaining chemostatic while others (e.g. DOC, SO24− and NO−3 ) behaved chemodynamically.<br/>
This indicates that the chemical composition of SSF depends on both the antecedent hydrometeorological conditions and local factors such as landuse, reinforcing the complexity of these processes. Our results highlight the dynamic nature of subsurface stormflow and the challenges involved in its characterization.
