Rising in the highlands of eastern Angola, the Okavango River flows southeastward, crosses a sliver of eastern Namibia and enters the northwest corner of Botswana. There, it spreads into a broad, braided delta which, during the cool,wet climate of the Pleistocene, fed a vast inland lake. As the climate warmed, this south-central region of Africa dried out, the lake receded into scattered salt pans and tectonic activity, associated with the East African Rift, altered the regional topography.
Through all of this, the Okavango Delta persisted, draining into the sands and seasonal lakes of the expanding Kalahari Desert; covering more than 6000 square miles, it is the largest inland delta on the planet. Flow through the Delta peaks from May through August, coinciding with the dry season of the surrounding grasslands and desert. As one might expect, this oasis effect attracts huge and varied concentrations of wildlife to the Okavango Delta, moving in from the parched landscape. Just as the Okavango flow begins to contract, in October-November, the wet season arrives on the adjacent plains and the herds disperse from the Delta.
With its slow percolation of fresh water across nearly flat terrain, the Okavango Delta is similar to the Everglades of South Florida, expanding and contracting with the seasons. Outlets to the south and east allow flow to continue through the year, minimizing salt deposition within the Delta; these outlet streams disappear into the sands of the Kalahari or end at saline likes, which, like those of the Great Basin, expand and recede as the balance between evaporation and inflow varies through the year.