There are many benefits from waterpower; demand for electricity, for example, is not constant, it fluctuates not only seasonally but daily, and even hourly. Hydropower generators are far more flexible than other sources of electricity and can respond to such variations. Furthermore, no direct environmental pollution is caused by a hydroelectric system, there is no fuel cost, and no consumption of natural resources that are irreplaceable and essential for other purposes. This said, in recent years, the significant adverse environmental effects of large hydro projects are being identified as a cause for concern. These environmental effects, both geomorphological and hydrological, are discussed using examples from six Arctic Scandinavian rivers. Statistical relationships between supply and demand of all energy, and potential devel9pments of hydroelectric supplies are presented. Nevertheless, although there are many problems associated with hydropower developments a great deal of research is currently investigating the ways in which these effects can be mitigated. The question still remains as to whether the benefits of the increasing use of hydropower justify the inevitable disruption of the Arctic environment.