Electricity generation steadily increased through the 20th century, peaking in the early 2000s. The long-term increase in generation from the mid-1950s shown here resulted from the building of large hydro-generation stations. The last of these was the Clyde hydroelectric station, which began operating in 1993. Since then, short-term ups and downs in hydro generation, resulting from rainfall variation, are more apparent. In a period of high rainfall, like 2004, the amount of hydroelectricity generated increases. During dry years, like those from 2005 to 2007, hydroelectricity generation falls.