BayCEER Workshop 2021

Investigating the Impact of Local Climate Change on Surface/Groundwater Interactions in Headwater Catchments

O 1.4 in Soil-vegetation-atmosphere interactions in a changing climate

14.10.2021, 16:36-16:48, H 36

Interaction between surface and subsurface water is an essential component for the surface flow in streams, particularly for those which are primarily dependent on the base flow. During drought conditions inflow of water from groundwater into streams is a prime water source and essential for ecosystems. In summer, dropping groundwater levels can be responsible for a disconnection between groundwater and stream, causing high infiltration rates and dried-up stream reaches. This phenomenon was increasingly observed in central Europe in the last years, particularly for headwater catchments due to climate change. Climate change is affecting not only surface water resources but also groundwater. Increasing groundwater temperatures and dropping water levels is clear evidence that climate change already has a significant impact on natural water resources. To understand this sensitive interaction between surface and groundwater in these systems, a process-based understanding is necessary. A fully integrated hydrological model (HydroGeoSphere) is used to assess the impact of local climate change to the Grosse Ohe catchment (Bavaria, Germany). A multi-scale model was set up, calibrated and validated for the years 2001-2021. The model was used to simulate and understand the interaction between surface and groundwater mechanistically. Different scenarios were simulated using projection from Regional Climate Change Models (RCMs) under three different representative concentration pathways (RCP2.6, RCP4.5 and RCP8.5) up to the year 2100. From projected scenarios, it can be observed that an increase in temperature is responsible for higher evapotranspiration rates, which significantly affects the water balance and water availability during summer. The model was used to identify reaches with preferential groundwater inflow and outflow. Simulations indicate that gaining sections more frequently turn into losing ones in future.

Keywords: Climate change, Integrated hydrological modelling, Forested catchment, Regional climate models

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