The temperature, water levels and flow will be modelled with HEC-RAS and with Computational Fluid Dynamics, CFD for two cases; Nidelva, Trondheim, Norway and part of Ume älv, Sweden for which geometrical data already exists and can be provided by Statkraft and Vattenfall. This will first be done for current running schemes of the turbines so that the models can be validated. Next, simulated flow that mimics typical turbine operations from WP2 will be used as input for the simulations and measured climate and other forcing data will be used to drive the models. Of importance is i) to figure out how large the natural damping in rivers is and how minor changes to the shore, like removing man-made weirs from timber rafting, for instance, influence the results. ii) Investigate how the technical mitigations as described in 5.1 influence the results and iii) give input to 5.3. This will result in new mitigation schemes that can be modelled and new input to 5.3 is generated. The work will be carried out by PhD-students at LTU and NTNU strongly supported by senior personnel at LTU, NINA, NTNU, NINA, Statkraft, Vattenfall and Lyse. For CFD calculations EDR will contribute with expertise.