High-resolution water quality simulation to disentangle multiple stressor effects on aquatic species

Stream ecosystems are impacted by multiple stressors in complex spatio-temporal interactions. The lack of understanding of these interactions and impacts hampers the successful restoration of streams and rivers. The German Research Foundation-funded collaborative research centre RESIST (https://sfb-resist.de/index.html) aims to disentangle these complex dependencies applying a novel theoretical framework: the ‘Asymmetric Response Concept’. The concept hypothesizes that degradation and recovery processes depend on different, non-linear biotic and abiotic interactions between stressors, environmental variables, and organisms. Therefore, unprecedented data and information are required which are collected through lab and field experiments, species sampling, observations of environmental variables and modelling.

High-resolution ecohydrological modelling is a core component in this process to provide historic information on water quality in two mesoscale catchments (Boye with 124km² and Kinzig with 1065km²) in Germany. Due to history, storage- and hysteresis effects in the hydrologic system, the spatio-temporal dynamics of in-stream environmental variables follow an asymmetric function to degradation and recovery. The model SWAT+ (Soil and Water Assessment Tool) is therefore applied to simulate streamflow as well as the water quality components temperature, oxygen, nitrogen components and salinity (TONS) at more than 20 sites in each catchment.

We present the conceptual framework of the approach, including data sources and data collection, model parameterization, required code adaptations, calibration techniques and expected results.