Located 4 km north-east of Nigel at an altitude of 1 585 m a.s.l., the Blesbokspruit IBA is a large, highly modified, high-altitude wetland with a narrow fringe of degraded grassland. It extends along the Blesbokspruit, one of the Vaal River's larger tributaries, from the Grootvaly Wetland Reserve (R555) in the north to the Marievale Bird Sanctuary (R42) in the south.
Water levels in the Blesbokspruit are artificially maintained by the inflow of mining, industrial and municipal effluents that are contained by embankments. The addition of organic matter produces the highly eutrophic conditions that are favoured by marginal vegetation. Reedbeds (Phragmites australis and Typha capensis) are estimated to cover more than 70% of the Marievale Bird Sanctuary (Joshua 2014) and the remainder of the IBA is similarly affected.
The average annual rainfall is 650–700 mm and temperatures vary from -10 °C in winter to 35 °C in summer (Koen et al. 2007).
More than 220 species have been recorded for the IBA in SABAP2. The Blesbokspruit, which in the past regularly supported 20 000 waterbirds, was designated a Ramsar Wetland of International Importance for waterbirds in 1986.
The water is highly productive, providing ample food for Lesser Flamingo Phoeniconaias minor and Greater Flamingo Phoenicopterus roseus. The system supports a diversity of waterbird species, including Goliath Heron Ardea goliath, Purple Heron A. purpurea, African Spoonbill Platalea alba, Glossy Ibis Plegadis falcinellus, Pied Avocet Recurvirostra avosetta, Red-knobbed Coot Fulica cristata and White-winged Tern Chlidonias leucopterus. African Marsh Harrier Circus ranivorus, which has been displaced from much of the surrounding veld as a result of intense industrialisation, urbanisation and habitat modification, is a breeding resident. African Grass Owl Tyto capensis is now rarely recorded along the Blesbokspruit, its local population decline being attributed to a reduction in its preferred rank grassland habitat adjacent to the wetland. Large volumes of water discharged upstream have increased the extent and permanence of flooded ground, while reed encroachment, unplanned fires, uncontrolled grazing by cattle and invasion by alien forbs contribute to the degradation of the remaining terrestrial habitat.
There is insufficient data to indicate that any species pass the IBA criteria. However, since the wetland is thought to hold more than 20 000 waterbirds, its importance for waterbird conservation should not be underestimated.
The Blesbokspruit was originally a perennial river with few or no reedbeds along its narrow banks and only a few expanses of open shallow water. During the gold rush of the 1940s, many buildings, roads and railways were constructed in this area, resulting in the creation of several large sand embankments that impeded the river's flow. The large, open, shallow stretches of water that subsequently formed were colonised by sedges, reeds, bulrushes, duckweed and other vlei vegetation. Large volumes of water now flow into the wetland and, together with insufficient drainage, have 'drowned' it. Prolific reed growth and almost permanently high water levels have reduced the extent of habitat available for wading birds. The additional water has also reduced the seasonally flooded 'wet meadow' and other suitable habitat for ducks, resulting in reduced numbers of Anatidae.
In May 1996 the Blesbokspruit was placed on the Montreux Record of priority sites for conservation action by the Ramsar Bureau because of the detrimental changes that have impacted the site and altered the ecological character of the wetland. Despite various interventions (such as the treatment of mine effluent and irregular reed management), duck populations have not recovered to historically high levels.
The IBA incorporates a 220-ha municipal protected area (Grootvaly Wetland Reserve) and a 1 012-ha provincial protected area (Marievale Bird Sanctuary) managed by the GDARD. Daggafontein, a 550-ha property that borders Marievale to the north, was donated to GDARD by AngloGold. However, due to financial and capacity constraints, this property has not yet been fully incorporated into the day-to-day management of the provincial protected area.
The rest of the properties between Daggafontein and Grootvaly are in the hands of private individuals and companies. This diverse ownership makes it difficult to implement conservation actions within the IBA. There is an environmental management plan for the reserve and the officer-in-charge is supported by a management plan committee that meets several times a year, as well as by the Friends of Marievale. The reserve is under-resourced and not all actions included in the management plan can be implemented at present.
Despite regular waterbird counts along sections of the Blesbokspruit, there are no reliable population estimates for individual species in the whole IBA. Although it is possible that some species, such as Spur-winged Goose Plectropterus gambensis, do pass the IBA criteria, this cannot be stated with certainty. The IBA does pass the sub-regional IBA criteria of 10 000 waterbirds and, on occasion, also the 20 000 waterbird criteria for a global IBA. More frequent monitoring and an intensive ringing programme are needed to better understand waterbird population dynamics at this site.
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Cowan GI, Marneweck GC. 1996. South African National Report to the Ramsar Convention 1996. Department of Environmental Affairs and Tourism, Pretoria.
Joshua Q. 2014. Reed spraying on Marievale Bird Sanctuary. Unpublished report. Gauteng Department of Agriculture and Rural Development.
Koen D, Green N, Mbatha KR, Mostert RE. 2007. Ecological Management Plan for Marievale Bird Sanctuary. Unpublished draft report. Gauteng Department of Agriculture, Conservation and Environment.
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