The Okavango Delta (or Okavango Grassland) (formerly spelled "Okovango" or "Okovanggo") 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.
All the water reaching the delta is ultimately evaporated and transpired and does not flow into any sea or ocean. Each year, about 11 cubic kilometres of water spread over the 6,000–15,000 km2 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.
The Okavango is produced by seasonal flooding. The Okavango River drains the summer (January–February) rainfall from the Angola highlands and the surge flows 1,200 km in around one month. The waters then spread over the 250 by 150 km area of the delta over the next four months (March–June).
The largest inland delta in the world, the Okavango Delta is the most unexpected wonder – water present in a desert. Dubbed “the river that never finds the sea”, this magical oasis spreads over more than 15 500 km² (almost 6 000 square miles) and yet is so fragile that, if it were denied water for even a decade, it would revert to a semi-desert.
The delta is very flat, with less than 2 m variation in height across its 15,000 km2, while the water drops about 60 m from Mohembo to Maun.