Biota in a river reach is influenced by various anthropogenic pressures (e.g. water quality, river training), which operate at different spatial scales:

  • Global scale: Climate change
  • Catchment scale: Discharge changes, water quality, nutrient input, (fine) sediment input
  • River network scale: River fragmentation (dams, weirs), missing riparian buffers, missing source population
  • Reach scale: River training



River restoration projects are often restricted to the reach-scale and water management can – at best – address pressures at the catchment scale. The remaining pressures at larger scales may limit the effect of restoration measures and river management actions at smaller scales. This might be the main reason why many small scale restoration and management measures only had minor effects on biota in the past.


The basic idea of the IMPACT project is to assess the relative importance of anthropogenic pressures operating at different spatial scales, and to identify the main bottlenecks for river biota. Different models will be coupled to predict the abiotic habitat conditions as well as the species pool available for colonization, and – based on these conditions – describe the fish and invertebrate assemblage that can be expected in the “receiving reach”.


The main research questions are:

  • What can you expect from local reach-scale restoration given the remaining pressures at larger spatial scales?
  • How important are discharge changes due to Climate Change compared to other anthropogenic pressures?
  • Will Climate Change have a major influence on natural reference conditions?

Impact figure on multiple pressures