Impact of Hydropower Plants on the River Hydromorphological Processes in the Context of Climate Change

The Hydropower plants (HPPs) directly affect river hydromorphology below the dam and cause the degradation of aquatic habitats. The impact of HPPs on the rivers system rapidly increased along with the effect of climate change. The main task of this research is to evaluate river hydromorphological changes in Lithuanian rivers under the influence of HPPs and the impact of climate change. Two Lithuanian rivers (Šešupė and Bartuva) were selected as case study objects. The hydromorphological surveys of river stretches below of the selected HPPs were done during the field works. For the projections of future river runoff, the hydrological models of selected rivers were created applying HBV software. The daily runoff projections for near and far future were simulated according to the ensemble of three RCMs outputs and two RCP scenarios. The results disclosed a strong relationship between hydromorphological units (HMU) and river discharge. At low discharges, some area of the river bed was lost, aquatic vegetation rose to the surface of the water and the HMU itself become to units with shallow depths and small velocity. The recurrence of low discharge situations will increase in the near and far future according to the simulated runoff projections. Such changes will create unfavorable conditions for the existence of the aquatic ecosystems, therefore, the environmental flow should be revised in the context of climate change.