Quantifying Groundwater Contributions To Streamflow Using a Multi-method Hydrological Approach

Water resources management is increasingly recognised as a global challenge, with surface water and groundwater systems playing crucial roles in sustaining ecosystems. In the Wüstebach Catchment, Germany, a multi-method approach was employed to investigate surface- and groundwater interactions. During field campaigns in November 2022 and February 2023, ground- and surface water samples were collected from 18 locations, in combination with Electrical Conductivity (EC), water temperature, stream discharge and groundwater level measurements. Additional discharge and precipitation data were obtained from the TERENO Eifel database. The EC measurements identified a gradual downstream dilution attributed to tributaries and contributing shallow groundwater with lower EC values. Chemical analyses showed the presence of diverse water types along the stream, with a dominant Na-Cl type observed on the western side of the catchment, possibly reflecting local differences in geology. Both temperature and groundwater level patterns indicated local groundwater-surface water interactions, for which the losing and gaining sections of the main stream were identified. Discharge measurements indicated substantial groundwater contributions, accounting for up to 74% of stream discharge. These findings stress the vital role of the groundwater in sustaining streamflow in the catchment, potentially mitigating drought vulnerability. The findings also show that it is possible to accurately map groundwater contributions to headwater streams by using this multi-method approach. This underscores the importance of a multi-method hydrological approach for informed water management, locally and globally.