The lakes are located between the towns of George (16km) and Knysna (40km) and adjoins the Indian Ocean on the Southern Cape Coast. It is managed by the Garden Route National Park (GRNP-WCS) formerly known as the Widerness National Park.
The Wilderness Lakes comprise a series of interconnected coastal lakes, parallel to the coastline, that are linked to an estuary and lagoon that opens periodically to the sea. Seawards of the wetland is an old consolidated dune which is vegetated with coastal fynbos and dune thicket, while inland of the wetland is a steep slope rising to a plateau. The slope is densely vegetated with coastal forest and bush. The Wilderness Lakes are one of the few coastal lake systems in Southern Africa. The Wilderness Lakes comprise a lagoon and floodplain of the Touws River, linked by a natural channel (the Serpentine) to the three lakes, Eilandvlei, Langvlei and Rondevlei. The lakes belong to the warm-temperate biotic province and together with the nearby Swartvlei system at Sedgefield are the only warm-temperate coastal lakes having a marine connection. The lakes’ temperature varies between 10-14˚C during winter and 25-29˚ during summer.
The lakes are situated on sands and alluvium of Pleistocene and Recent age against a back-drop of steep Tertiary-age sea cliffs on the north side and Pleistocene-age fossil dunes on the south side. The system in its present form is thought to have formed about 7 000 years ago. Between 45 000 and 10 000 years ago, during the periods of glaciation in the northern hemisphere, the sea alternately covered the entire area of the Wilderness Lakes to the base of the cliffs of the Tertiary-age uplands during warm periods, and then receded with the formation of the northern ice-caps. Then, with the end of the northern hemisphere glaciation, strong coastal winds associated with increased land temperatures led to the formation of coastal dunes. The dunes blocked the estuaries which resulted in basins forming inland of the dunes, and these lakes or barrier lagoons occasionally broke through to the sea. The Wilderness Lakes have been formed by the segmentation of an earlier lagoon.
The maximum depths of the different waterbodies are as follows: Touw River = 3 m, Island Lake (Eilandvlei) = 4 m, Langvlei = 3 m and Rondevlei = 4 m.
As to why these coastal lakes form here and not elsewhere – it is partly climatic and partly because the underlying geology permits it there and not elsewhere. Being soft, the rocks here are more susceptible to valley formation than is possible in hard granites and quartzites where deep vertical-sided gorges are all that the rivers can managed.
In the Wilderness system, the best lakes for birding are Langvlei and Rondevlei, largely because both have well-positioned hides which are accessed along boardwalks cut through dense reedbeds. These hides, especially the one at Rondevlei, are excellent places to search for stubborn skulkers such as Red-chested Flufftail and African Rail. The best way to see these birds is to lure them across the gap in the reeds formed by the boardwalk. Baillon’s Crake also occurs here, but is less likely to be enticed into view and is best searched for at the reed edges in the early morning. Rallids aside, the lakes offer a pleasant selection of more conspicuous species, including Yellow-billed Egret, Purple Heron, African Fish Eagle, Osprey (summer), African Marsh Harrier, Malachite Kingfisher and Cape Reed and African Sedge Warblers.
Questions:
1. Of what does the Wilderness Lake System comprise?
2. When was the Wilderness Lake System formed?
3. What is the maximum depth of Island lake (Eilandvlei) which lies to your left when standing at the given coordinates?
4. What is your approximate elevation at the given coordinates?
5. Of which South African National Park are the Wilderness lakes system a part of?
6. Submit a photo at one of the Wilderness Lake System components (optional).
NOTE: Please do not post your answers in your log. Mail them to the CO for review. Any logs not accompanied by an email will be deleted.
References:
http://www.ngo.grida.no/soesa/nsoer/resource/wetland/wilderness_ris.htm
Garden Route National Park – Wilderness Coastal Area, SANPARKS, by I A Russel, R M Randall, N Cole, T Kraaij & N Kruger
The book, Geological Journeys – A traveller’s guide to South Africa’s rocks and landforms by Nick Norman & Gavin Whitfield