A vlei is a geographical feature characterized as a shallow minor lake that is typically seasonal or intermittent in nature. These areas can manifest as seasonal ponds or marshy patches, often serving as breeding grounds for frogs and other marsh-dwelling species.
The extent of a vlei, and its presence of water, fluctuates based on the amount of rainfall or the specific dryness of the season. Depending on environmental conditions, vleis can be freshwater, saltwater, or brackish. Over time, these features may degrade into clay pans or salt pans, such as Sossusvlei or Dead Vlei.