The Upper Orange River IBA (formerly known as Gariep Oviston Tussen-Die-Riviere IBA) consists of a set of reserves that surround the Gariep Dam on the Orange (Gariep) River. The Gariep Dam Nature Reserve covers most of the dam and the northern section; the Tussen-Die-Riviere Nature Reserve lies in the east wedged between the Caledon and Orange rivers; and Oviston Nature Reserve is in the centre. The smaller ephemeral rivers running to the dam are the Bossiesspruit, Brakspruit, Broekspruit, Oudagspruit, Palmietspruit and Slykspruit.
The landscape is generally flat plains that are interrupted by low hills and river valleys. The terrain between the Orange and Caledon rivers comprises rocky ridges and ravines interspersed with areas of open plains. The highest peak, Heuningkop (1 520 m a.s.l.), is on the eastern boundary. Approximately 95% of the landscape in this IBA is in a natural state and 5% has been degraded or transformed. The town of Bethulie is on the northern boundary of this IBA and there is a large resort at the Gariep Dam wall.
This IBA falls within the Nama Karoo and Grassland Biomes. The landscape can be divided into five major vegetation types: Upper Gariep Alluvial Vegetation along the Orange River (Vulnerable), Xhariep Karroid Grassland, Eastern Upper Karoo, Besemkaree Koppies Shrubland and Highveld Salt Pans. The ecosystem status of the last four vegetation types is Least Threatened.
The dam regularly supports impressive assemblages of waterbirds, including significant numbers of Egyptian Goose Alopochen aegyptiaca, South African Shelduck Tadorna cana and Yellow-billed Duck Anas undulata. Caspian Tern Sterna caspia also frequents the dam and breeds on one of the islands. Greater Flamingo Phoenicopterus roseus is present in low numbers. The water level of the dam fluctuates as water is released for electricity generation and irrigation and this is likely to lead to fluctuations in waterbird and wader numbers.
A few hundred Blue Cranes Anthropoides paradiseus roost on an island in the dam and feed in the karroid vegetation around it. Other typical karroid species that are frequently seen in the reserves surrounding the dam are Ludwig's Bustard Neotis ludwigii, Karoo Chat Cercomela schlegelii, Sickle-winged Chat C. sinuata, Layard's Tit-Babbler Sylvia layardi, Namaqua Warbler Phragmacia substriata and Black-headed Canary Serinus alario. In areas where grasses dominate the Karoo vegetation both Blue Korhaan Eupodotis caerulescens and Karoo Korhaan E. vigorsii are common.
At the time this IBA was assessed, its 32 pentads had been poorly atlased. The total number of species recorded during both SABAP1 and SABAP2 is 274, and 234 species have been recorded so far during SABAP2.
CWACs at the Gariep Dam have been irregular, with the last count completed in summer 2011 (B Colahan CWAC data). The total number of waterbirds occasionally rises to more than 10 000, but is usually fewer than 10 000. The 2011 counts recorded Egyptian Goose, South African Shelduck and Yellow-billed Duck as most abundant.
A nesting pair of Secretarybirds Sagittarius serpentarius was recorded in October 2014 in the Gariep Dam Nature Reserve. Martial Eagle Polemaetus bellicosus and Tawny Eagle Aquila rapax have been reported breeding in this IBA, but not breeding in 2014. Verreauxs' Eagle Aquila verreauxii is frequently seen. Kori Bustard Ardeotis kori, Grey Crowned Crane Balearica regulorum, Western Osprey Pandion haliaetus and Amur Falcon Falco amurensis have been recorded during SABAP2.
Globally threatened species are Blue Crane (100–300; B Colahan CWAC data), Blue Korhaan, Melodious Lark Mirafra cheniana, Ludwig's Bustard and Secretarybird (breeding). Regionally threatened species are breeding Caspian Tern (450 birds; B Colahan CWAC data), Karoo Korhaan, Greater Flamingo and Verreauxs' Eagle. Karoo Chat, Sickle-winged Chat, Layard's Tit-Babbler, Namaqua Warbler, Black-headed Canary and Pale-winged Starling Onychognathus nabouroup are biome-restricted species. Congregatory species include Egyptian Goose, Yellow-billed Duck and South African Shelduck.
One of the most important threats is the water fluctuation of the Gariep Dam. The Gariep and Vanderkloof dams are regulated for hydropower generation and to satisfy downstream demands for irrigation. Escalating demand for water from the Orange River for human consumption and industrial and agricultural purposes is placing increasing stress on the Orange River system. The functioning of the Orange River and the Gariep Dam will be altered significantly with the full implementation of the Lesotho Highlands Water Scheme. There is a possible threat of sedimentation in the eastern section of the dam, as regulated flow from the Caledon River and Lesotho prevents flooding and there is severe soil erosion in the Lesotho highlands.
Predictions on climate change for South Africa state that temperatures will increase and rainfall decrease sharply in arid areas. In the central regions of South Africa, climate change scenarios predict that by 2050 summer rainfall will be slightly higher, and it may also become more variable. Droughts are predicted to become more severe due to climate change, and responses to drought may be species specific. At this stage species-specific responses are difficult to predict and research in this field is in its infancy. Bush thickening and/or encroachment is expected to increase with increased atmospheric carbon levels.
Renewable energy developments are a new threat in the region. At this stage no solar or wind energy facilities have been approved or proposed for development within this IBA. However, three renewable energy facilities have been approved for development nearby. Possible impacts of solar energy facilities on the IBA trigger species are collisions with power lines and reflective solar panels, and breeding disturbance during construction. Some of the trigger species in this IBA, such as Ludwig's Bustard, Blue Crane, Blue Korhaan, Martial Eagle, Tawny Eagle and Greater Flamingo, are predicted to be highly susceptible to wind energy facilities and moderately susceptible to solar energy installations.
Other important threats within this IBA include collisions of Blue Crane, Blue Korhaan and owls with power lines.
Applications have been made for shale gas exploration, which is likely to be by means of hydraulic fracturing, around this IBA. There is therefore a potential threat of fracking over the medium term around the IBA, but its formal protection status may exclude such activities within it.
This IBA is formally protected. The Oviston Nature Reserve, Tussen-Die-Riviere Nature Reserve and Gariep Nature Reserve were proclaimed in 1968, 1972 and 1979 respectively. They were initially managed as separate units. Recently it was proposed that these three conservation areas be managed together as a single conservation area using a joint management plan. The Free State DETEA manages the entire IBA area. The DWA controls the flow of water into and out of the dam. This seldom caters for the needs of the dam's waterbirds.
The area was previously farmland, as is evidenced by the patches of soil erosion and intensive grazing pressure. The vegetation has been steadily recovering since the livestock have been removed. The land surrounding the IBA is used for sheep grazing.
Regular bi-annual CWACs were undertaken to monitor waterbird numbers, but were discontinued in 2011.
The Free State DETEA has purchased a farm (Katfontein) next to Tussen-Die Riviere Nature Reserve, which is 2 350 ha in extent. There are expansion plans for a neighbouring stewardship area that will include Bethulie and a section westwards. This will increase the conservation area by 120 000 ha.
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