Swiss rivers have a large potential for energy production from hydropower and there is currently a push towards to construction of small hydropower plants (SHPs, <10 MW). Since the early 20s there were about 7000 SHPs running and the potential of further SHPs expansion is estimated in an annual increase of about 2,200GWh which is interesting for the planning of the “Energiestrategie 2050” to cover the loss of energy production from opting out of the nuclear energy program. However, the impact of SHPs on biodiversity and the provisioning of ecosystem services is not well known. In this study I sought to investigate whether SHPs have an impact on Swiss alpine river ecosystems, with special focus on the macroinvertebrate community and brown trout (Salmo trutta) foraging ecology, by studying near-natural and impacted stream reaches of five SHPs in Graubünden (Switzerland). I analyzed environmental data, benthic macroinvertebrate community composition and brown trout somatic condition and stomach contents. I found no significant differences but trends for benthic macroinvertebrate communities in residual reaches which might reflect a negative influence of SHPs and could be explained by environmental variables. Residual flow reaches had a more stable river channels, lower current velocities, significantly lower discharges and lower organic matter concentrations. Trout had a significantly lower somatic conditions in residual reaches compared to downstream reaches and it also tended to be lower than in upstream regions. Trout from residual reaches fed disproportionally more on EPT taxa than there were available in the benthic invertebrate community. This feeding pattern might have come at the cost of a higher energy expenditure and therefore led to reduced body condition. My study shows that SHPs had substantial impacts on stream habitat and ecosystem processes. Further, I could show that the reduced trout somatic condition in residual flow reaches may be a result of shifts in invertebrate prey availability.