Zandvlei is an estuary located in the south-western corner of the Cape Flats, near Muizenberg, a small coastal town on the False Bay coastline. The reserve was started when 22 ha along the northern shore of the vlei was proclaimed the Zandvlei Bird Sanctuary in 1978. This was enlarged to 204 ha with the proclamation of the Greater Zandvlei Estuary Nature Reserve (the expansion of the boundaries) on 26 October 2006 in terms of Provincial Gazette 6389/27, October 2006 (PN 344/2006).
The reserve lies some 20,4 km from Cape Town.The catchment for the Zandvlei estuary falls entirely within the boundaries of the City of Cape Town, and is bordered by the Muizenberg mountain, Silvermine plateau, Constantia mountain, Cecilia Ridge, Wynberg Hill and a less conspicuous watershed along the eastern boundary.
It is a relatively small catchment, comprising an area of 92 km2, or 9,655 ha, and is drained by a number of rivers and streams, of which the main ones are the Little Princess Vlei stream, Westlake stream, the Keysers river, Langvlei canal and the Sand river canal/Diep river.
These rivers converge on Zandvlei, with the Keysers river and Westlake stream entering it through an extensive reed bed on its north-western margin, while the Sand river canal enters the vlei west of Wildwood Island. The wetland area covers some 60 ha, while the main body of the vlei is 56 ha.
In addition, the system includes a marina of 31 ha along its eastern margin, and an outlet channel of 9 ha, which links to the sea on the north-western shore of False Bay.