A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines. This penstock leads to an Hydro-electric power plant.
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy.
Norway lies 6th in the table of hydroelectric producers, and approximately 99% of the country's electricity is produced in this way.
As a matter of interest, the amount of rainfall/snowfall affects the price of electricity.