Complex sentence: The reservoir was formed in the early 1970s as a result of the dam construction by the Hydro-Electricity Commission of Tasmania in order to create an upper storage for the Gordon Power Station, the largest and most controversial hydro-electric power scheme in Tasmania.
Split into simpler sentences: The reservoir was formed in the early 1970s as a result of the dam construction by the HEC. It was the largest and most controversial hydro-electric power scheme in Tasmania.