Rivers and streams are higbly dynamic ecosystems of particular divenity. Over the course of the past two centuries humans have considerably modified river ecosystems, also by exploiting hydropower for electricity production. There are three major impacts from hydropower exploitation: interruption of the longitudinal connectivity, residual flow and hydropeaking. In this article we present selected examples on how these impacts affect the riverine organisms, their habitats and the processes that shape and maintain these habitats. In the second part of the article we discuss ongoing and future changes in the hydropower exploitation in Switzerland as they are initiated by the revised water protection act and the planned phasing-out of nuclear power.