RESIST - Long-term multi-stressor trajectories in Central European rivers

Rivers and their ecosystems are shaped by a complex interplay of natural processes and human activities. Many ecosystem stressors are affected by hydrological processes and extremes, but their interactions are still poorly understood, particularly at the large scale. In A24, we investigate how multiple environmental stressors - such as drought, water temperature, salinity, and biological oxygen demand (BOD) - interact and impact river systems in Central Europe over several decades. Our goal is to better understand the long-term dynamics of river degradation and recovery in the face of climate change and increasing human pressures.

A key focus of our research is the close connection between surface water and groundwater. Groundwater provides essential baseflow to rivers, especially during dry periods, thereby maintaining ecological flow. The interaction between surface water and groundwater is crucial in times of droughts, but it depends on local conditions and varies across space and time. To capture these dynamics and improve the simulation of low flows and desiccation events, we integrate the gradient-based groundwater model G³M with the WaterGAP3 framework. The modelling framework also accounts for human activities such as water use, reservoir management, and pollution input that affect water resources in terms of both quantity and quality. Additionally, we use the WorldQual model to simulate water quality parameters (water temperature, salinity, BOD). All models operate at a spatial resolution of 5x5 arcminutes (approximately 9x9 km at the equator).

This model integration allows us to simulate low-flow conditions, desiccation events, and their effects on water quality in Central Europe over the past 70 years. The coupled model will be tested and validated against freely available streamflow and groundwater level observations. We will compare our large-scale results on groundwater recharge and baseflow with those from the physically based SWAT+ model for the Kinzig catchment and assess the potential for further model improvement. The outcomes of A24 are relevant for the upscaling of ecological findings and improve understanding of timing and duration of river degradation and recovery phases.