Welbedacht Dam Wasconstructed Mainstorage Asthe Water Caledon–Modderrivergovernment Elementofthe Purpose Storage Levelof1,385.2 Mandreservoir At1,383.2 M
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WELBEDACHT DAM South Africa NAMIBIA BOTSWANA COORDINATES (degrees, minutes, seconds) LATITUDE LONGITUDE Orange-Senqu 29° 54’ 32” S 26° 51’ 38” E River Basin Welbedacht Dam LESOTHO LOCATION SOUTH AFRICA This dam is situated on the Caledon River near Wepener in the Free State in quaternary D23J, South Africa. DESCRIPTION The Welbedacht Dam is a concrete barrage-type dam. The dam has a full supply level of 1,402.9 m, with a dead storage level of 1,385.2 m and reservoir bottom at 1,383.2 m. PURPOSE Welbedacht Dam was constructed as the main storage element of the Caledon–Modder River Government Water Scheme (CMRGWS) and water is abstracted from this dam for transfer to Bloemfontein and various smaller users along the way. Its purpose was to supply water to the city of Bloemfontein via the 115-km-long Caledon– Bloemfontein pipeline which has a capacity of approximately 1.157 m3/s. Due to the high sediment concentration in the water, the transfer from Welbedacht Dam is first purified at the Welbedacht Purification Plant which is located just downstream of the dam. The purification plant has a capacity of 1.68 m3/s (145 Mℓ/day). 3 3 The storage capacity of the dam reduced from 115 million m to approximately 16 million m in only 20 years Welbedacht Dam (source: www.ewisa.co.za) due to siltation. This impacted the assurance of supply to Bloemfontein and so Knellpoort Dam was constructed to augment the supply. From: The Orange–Senqu River Basin Infrastructure Catalogue, ORASECOM Report 001/2013 WELBEdaCHT DAM PHYSICAL INFORMATION Modder Krugersdrift Dam Bloemhof Dam Catchment Quaternary FSC* 2 Wall height Wall length Dam name River 3 FSA (km ) Owner DWA code Mazelspoort Weir catchment (million m ) (m) (m) Bainsvlei W Mockes Dam Kor anna Hamilton Park Welbedacht Caledon D23J 15.47 11.75 DWA D2R004 32 192 BLOEMFONTEIN Bloemdustria Brandkop Boesmanskop Bloemspruit Sepane Thaba Nchu * Live full supply capacity (ORASECOM, 2007a, WRYM datasets and DWA, 1990) Mo dd De Brug e Seroalo Dam Grootvlei r Newbury Botshabelo Dam Bloemdustria 3 Lovedale Demands/abstractions (million m /a) Kgabanyana Dam W 1:50 yield (million Maximum spillway Kle Year of completion 3 3 Rustfontein in m /a) capacity (m /s) Lesaka Dam Modder Groothoek Dam Armenia Domestic Irrigation Other W Dam Caledon–Bloemfontein 1973 48.27 † Unknown 1166 ‡ Unknown 5,310 Ganna † WRC, 2008 Leeu ‡ Total outflow from the dam (WRC, 2008) Riet–Modder Catchment Uitkyk DEWETSDORP SOUTH AFRICA REDDERSBURG Caledon LESOTHO Riet Peri-urban area/urban area P P Town Knellpoort Dam Tienfontein International boundary River and dam Welbedacht Dam De Hoek Pipeline and reservoir Caledon W Proposed canal Catchment Watershed N Caledon W Water purification works P Pump station 0 5 10 15 20 25km Caledon–Bloemfontein Government Water Scheme (adapted from ORASECOM, 2007a) WELBEdaCHT DAM ARea–CAPACITY RELATIONSHIP Elevation (m) Storage (million m3) Surface area (km2) 1,403.4 22.25 14.20 1,403.1 18.18 12.88 1,402.9 15.47 11.75 1,402.5 11.45 9.29 1,402.3 9.74 7.85 1,401.7 6.21 4.30 1,401.3 4.78 2.90 1,400.5 3.19 0.44 1,385.6 0.01 0.01 1,383.2 0.00 0.00 OPERATING RULE Welbedacht Dam (along with Knellpoort Dam) supports the Modder system when there is insufficient water in the system, via the Caledon–Modder Transfer. Welbedacht Dam is heavily silted (© UNOPS/Leonie Marinovich).