The Okavango Delta in Botswana is a swampy inland delta formed where the Okavango River reaches a tectonic trough at an altitude of 930–1,000 m in the central part of the endorheic basin of the Kalahari.
and does not flow into any sea or ocean. Each year, about 11 cubic kilometres (2.6 cu mi) of water spreads over the 6,000–15,000 km2 (2,300–5,800 sq mi) area. Some flood waters drain into Lake Ngami. The area was once part of Lake Makgadikgadi, an ancient lake that had mostly dried up by the early Holocene.