At the lower end of the Bot River with its fresh mountain water, lies the Bot River Estuary. A smaller river, the Afdaks River also feeds the system. A narrow channel, known as the Keel, connects the Bot River Estuary to the Kleinmond Estuary. The Lamloch River feeds the latter system. Residents of the coastal towns Kleinmond, Hawston and more inland Botrivier and Caledon, have free access to this unique wetland area. The entire aquatic system covers 20 square kilometres – making it one of the largest wetland systems in South Africa’s Western Cape. What is also quite remarkable of this estuarine system is the free flow of water between the two estuaries, in either direction, via the Keel. Located within the Rooisand Nature Reserve, this channel is under the close monitoring of conservationists. The significance of this connection is that aquatic life, birds and mammals can freely move between the two estuaries.
Today, the system is a semi-permanent closed system, although historically it was a permanently open system. Occasionally, with heavy rainfall, the estuary breaches naturally and water flows out to the sea. Like most estuaries along South Africa’s coast, the Bot River and Kleinmond estuary systems can not escape artificial breaching. A number of habitats are associated with the combined Botrivier and Kleinmond estuarine systems, highlighting the biological diversity of this system. Habitats recorded for the system include river habitat, open water, shoreline, mudflats, sandflats, marsh and reedbeds. Considering these habitats, it is not surprising that the aquatic, bird, fauna and flora life found here is quite something.
A feature characteristic of all species associated with the wetland system is the ability to tolerate both fresh and brackish waters. This is however a restraining factor, capping the wetland system’s biological diversity. Up to 60 waterbird species have been recorded for the wetland system, with summers bringing a solid influx of migrating waterbirds. It is particularly the Great Crested Grebe, Blacknecked Grebe, Yellowbilled Duck, Cape Shoveller, Harlaub’s Gull and Redknobbed Coot flocks, attracting avid birdwatchers. The vulnerable African Marsh Harrier also calls the wetland system home.
Fish species are abundant, offering good food stock for avifauna and favourable fish hunting for local fisherman. The 32 fish species found within the system, is described according to breeding grounds: estuary breeders, open sea breeders, estuary and open sea breeders, and freshwater breeders. The recent discovery of previously unknown estuary breeder, Clinus spatulatus, a klipvis, made headlines as it is thought to be endemic to the Bot River estuary. The wetland system is highly favoured by fisherman, both for recreational and commercial purposes.
Although present due to historical human influences, the Kleinmond Wild Horses is a well-known sight of the wetland system. The herd of horses, although somewhat adapted to human presence, is Southern Africa’s only wild horse population living within the confines of a wetland system. This little herd has shown remarkable physical adaptation to marsh living. Over less than a century, this herd has developed saucer-shaped hooves in response to the wetland environment and constant water and soggy soils beneath their hooves. Legend has it that this population of free roaming horses date back to the Anglo-Boer War, with the escape of local horses from the war scenes.
Life in the wetland system is peaceful yet dynamic. But there is one major environmental concern, a human induced concern, that is a major threat to the entire wetland system and the ecology it supports – artificial breaching on a regular basis. Natural breaching is only likely to occur at 3,0 metres above mean sea level, but long before reaching this level, backing estuary waters threaten development, infrastructure and private property within the floodplain. As estuary waters rise, property owners pressurise authorities to take action; recent artificial breachings took place at 2.6 metres above mean sea level. The Bot Rivier and Kleinmond estuaries have shown a steady drop in natural breachings – and this too is due to human influences. The inflow of water to the systems have reduced notably within the last few decades, with freshwater inflow 25% lower than previous decades. Increased water abstraction from the feeding rivers for agricultural, domestic and municipal use, damming and catchment infestation by invading and water-thirsty plants are the major reasons for reduced water flow to the wetland systems. The estuary’s weaker flow is unable to prevent sediment build up at the mouth opening, resulting in the need for artificial breaching. Artificial breaching has several downfalls: there is no proper flush of sediment build-up, salinity levels increase (with associated habitat impacts), and water levels drop significantly within a few hours causing a small environmental catastrophe after each artificially breaching.
Future of the Bot River and Kleinmond Estuaries
These two systems, forming a larger and joined wetland area, is in the fortunate position of having a well-developed Estuary Management Plan in place. It is also found within the borders of the UNESCO registered Kogelberg Biosphere Reserve, lending the system a fair degree of protection. There is however a need for a long-term holistic management approach. Man should be careful not to alter the true nature of this system – wetland changes can happen abruptly, yet should not be allowed to happen due to conflicting human desires.
The Rooisand Nature Reserve offers a valuable corridor between the Bot River and Kleinmond Estuaries.
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Sources: University of Cape Town, Avian Demography Unit, 2002; African Wildlife, Volume 40 No. 6; Overstrand Estuary Management Committee
Photo credits: copyright Word from the Savanna & some rights reserved by Tina Phillips via freedigitalphotos.net