Lake Kariba, reservoir, southern Africa, an expansion of the Zambezi River. It is formed by Kariba Dam (built 1955-1959), a great hydroelectric facility that straddles the border between Zambia and Zimbabwe. The dam, a concrete-arch structure, is 128 m (420 ft) high and has a length along its crest of about 610 m (about 2000 ft). Lake Kariba extends upstream for 282 km (175 mi), through Kariba Gorge, and has a maximum width of about 40 km (about 25 mi). When the lake was formed, in 1960 and 1961, some 50,000 persons required resettling, and many wild animals were evacuated in a project called Operation Noah.