Complex sentence: In 1960, the Koka Dam was completed across the Awash River at a point about 75 kilometers from Addis Ababa, and with its opening became a major source of hydroelectric power in the area.
Split into simpler sentences: In 1960, the Koka Dam was completed across the Awash River at a point around 75 kilometers from Addis Ababa. With its opening, it became a major source of hydroelectric power in the area.