BayCEER Workshop 2023

Tracing Longitudinal Patterns of Subsurface Hillslope-Stream Connections Across Catchments

Subsurface stormflow (SSF) originating on hillslopes is a fundamental hydrological phenomenon contributing to streamflow generation in headwater catchments. The extent of the contribution of SSF to streamflow generation especially at catchment scales is still unclear due to the complex nature of tracing hillslope-stream SSF signals. The riparian zone can act as a buffer zone, altering the physical and chemical attributes of SSF before entering the stream. Consequently, SSF may not be recognized as a streamflow contribution.

This study aims to characterize SSF hillslope-stream connectivity at the reach-to-catchment scale, using physical and chemical information. The study implements a novel multi-method experimental design that will create a unique along-stream data set of hillslope contributions to streamflow in four different catchments. A combination of in-stream and shallow groundwater level monitoring, longitudinal radon profiles, and the chemical analysis of shallow groundwater and stream water will enable the evaluation of SSF hillslope-stream connectivity at larger scales.

Here, we present data obtained in one of our test catchments in Germany. We demonstrate the hydrochemistry data obtained from two stream water and groundwater snapshot samplings. Using in-stream radon profiling data and a numerical modeling tool (FINIFLUX), we also quantify the contributions of groundwater inflow to streamflow. We ultimately aim to develop a framework for assessing subsurface hillslope-stream connectivity at the catchment scale.