Tracing subsurface flow paths from hillslopes to streams using a multi-method approach

The identification of lateral flows on hillslopes is a challenge because this is an invisible process with pronounced spatial variability that is influenced by a variety of factors. However, identifying the signal of hillslope contributions, especially interflow, in the stream is even more challenging because this signal can change not only during passage through the riparian zone, but also directly before entering the stream.

Our innovative cross-scale experimental approach within the DFG research group on Subsurface Stormflow (SSF) includes the monitoring of flow captured in trenches but also the spatially distributed recording of groundwater dynamics in the riparian zone during both natural events and salt tracer injection experiments. This is complemented by the analyses of water chemistry and thus potential SSF tracers both in hillslope subsurface flow and in groundwater and stream water. Additional campaign-based measurements include salt dilution tracer experiments, measurements of radon concentrations and patterns of temperature anomalies identified in the stream channel with both fiber optic temperature sensing and thermal infrared imagery, using heat as a tracer for groundwater inflows. This presentation will give an overview of the first results of the project.