Study area and species data

Our study areas were the Kinzig River catchment, characterized by a moderate gradient, fine-coarse sediment, surface runoff and interflow, and the Treene River catchment, with a small gradient, sand-gravel sediment, and groundwater-driven conditions, which are located in the central lower mountainous region and northern lowlands of Germany, respectively (Fig. 1)^13,27. We used 134 macroinvertebrate species from 223 sampling sites in the central lower mountainous region and 60 species occurring at 67 sites in the northern lowlands, yielding 150 unique species from 15 taxonomic orders (Table ST¹, see Kakouei et al.¹³ for the sampling procedure). Prior to modeling, we aimed to reduce potential uncertainties deriving from species data by excluding sampling sites with a “poor” or “bad” ecological status according to the monitoring required by the European Water Framework Directive.

The study area⁵⁷: The Treene catchment in the northern lowlands with 67 sampling sites (a) and the Kinzig catchment in the central lower mountainous region with 223 sampling sites (b) in Germany.