The European Water Framework Directive requires to improve the ecological status of all surface waters that do not meet “good ecological status”, and hence, there is an urgent need for (cost)-effective restoration measures. Many different restoration measures have already been applied but only few projects have been monitored and knowledge on the effects is still limited.

The few monitoring results indicate that many restoration measures did not significantly improve the ecological status. There is statistical evidence that pressures at different spatial scales influence river biota and that pressures at larger scales may limit the effect of restoration measures which usually are applied at the reach-scale.

However, there are limited information on the governing processes and an urgent need for experiments and modelling to investigate how river network and catchment scale pressures constrain the effect of local restoration and management measures, especially in the light of Climate Change.

The main objective of the IMPACT project is to model how large scale pressure impact river biota in river reaches, including pressures at the river-network scale (e.g. migration barriers, missing source populations), catchment scale pressures (land-use), and the most important global scale pressure: Climate Change.