The Okavango Delta (or Okavango Grassland) in Botswana is a very large inland delta formed where the Okavango River reaches a tectonic trough 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 approximately 11 cubic kilometres of water spreads over the 6,000-15,000 km² area. Some flood-waters drain into Lake Ngami. The Moremi Game Reserve, a National Park, is on the eastern side of the Delta. This statistical significance helped the Okavango Delta secure a position as one of the Seven Natural Wonders of Africa, which were officially declared on February 11, 2013 in Arusha, Tanzania.