Phase 2A: De Hoop Dam
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15-Feb-2008 12:43 PM
  
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PHASE 2A: DE HOOP DAM

Background

President Mbeki announced in his 2003 State of the Nation Address announced the construction of a dam in the Olifants River system to unlock the rich mineral deposits in the Limpopo Province and to economically supply water to towns, industries and poorly serviced rural communities in the Sekhukhune area.

The Phase 2A of the ORWRDP was approved by Cabinet in June 2004 subject to environmental authorisation. It comprises the implementation of the De Hoop Dam on the Steelpoort River in the short term and bulk distribution system in the middle Olifants River catchment in the medium to longer term as the need for water services and mining increase. The De Hoop Dam is the only feasible option to supply water tot he Nebo Plateau where about 800 000 people reside.



click for larger view - dam illustration


Project Scope

The main aim is the construction of a large storage dam at De hoop on the Steelpoort River to commence partial impoundment and delivery of water by the spring of 2009 and final completion and commissioning during 2011.

A section of the provincial road P169-1 (R555) between Middelburg and Burgersfort will be submerged by the future dam and therefore requires realignment. The realigned route of about 20 km will pass the new dam on the western side and includes two bridges over the Steelpoort River.


click for larger view - dam illustration

 

Main Features of the De Hoop Dam

Catchment Area 2 865 km2 1 : 5 Year Flood 206 m3/2
Mean Annual Precipitation 706 mm 1 : 20 Year Flood 502 m3/2
Mean Annual Runoff 116 million m3 1 : 50 Year Flood 804 m3/2
Gross Reservoir Capacity at F.S.L. 347 million m3 1 : 1000 Year Flood 1 100 m3/2
Spillway Discharge at H.F.L. (1 : 200 years) 1 104 m3/s Regional Maximum Flood 3 520 m3/2
Maximum Capacity of Outlet Works 20 m3/s Full Supply Level RL 915 m
Maximum Spillway Capacity 3 616 m3/s Lowest Drawdown Level RL 875 m
Volume of Concrete 750 000 m3 Overall Length of Dam Wall 1 015 m
Volume of Excavation 250 000 m3 Length of Spillway 110 m
Annual Yield 80 million m3/s Lowest Foundation Level RL 840 m
Reservoir Surface Area at F.S.L. 5 300 m3/s Maximum Wall Height 81 m

 

Land Matters

Twenty one privately-owned farms/properties are affected by the De Hoop Dam basin.

All these properties, together with the whole basin and proclaimed conservation area have been purchased. Additional land has been acquired for the establishment of a conservation area as dictated by the RoD.

Some counter claims have been received and the valuator is currently in the process of evaluating these claims.

The process to acquire land in Roossenekal started in September 2007. A report on the unregistered rights has been completed and submitted to the Land Affairs Board. DWAF is still awaiting the outcome.

 

Conservation

According the specialist vegetation study reports, 295 plant species exist in the dam basin, of which 19 are highly sought after and widely used in the Steelpoort Valley, either as medicine, food, firewood, or for magical or utility purposes. Of these species, 4 are in such high demand, that they are now endemic or near-endemic tot he Sekhukhune Centre of Plant Endemism (SCPE), and one is a Red Data species.

The project area was declared a National Conservation Forest, gazetted on 6 July 2007. According to the National Forestry Act this land is now protected under State Law and no wood harvesting is allowed and is illegal.

DWAF is planning on acquiring the services of a contractor who will be responsible to remove all the wood that will be inundated in the dam basin to an agreed area near the dam.

 

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Maximum Wall Height: 81 m
Overall Length of Dam Wall: 1 015 m
  Annual Yield: 80 million m3/s
  Catchment Area: 2 865 km2
  Gross Reservoir Capacity at F.S.L.: 347 million m3
Length of Spillway: 110 m
 


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