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Inter-Basin Water Requirements and Resource
availability
The National Water Act (Act 36 of 1998) requires the DWAF to implement a national
water resource management strategy that will provide a framework for the protection,
use, development, conservation, management and control of water resources for the
country as a whole, and also on a regional or catchment level.
Included in this strategy is the provision of the Environmental Reserve, the
amount of water that is required to meet social and ecological needs. Sophisticated
water resource system analysis modelling techniques are used to determine the
in-stream flow requirements that are necessary to maintain the Reserve. In terms of
the Thukela River Catchment, the Reserve must be met prior to making decisions on
major water use, such as considering inter-basin transfers.
Using in-stream flow estimates and 2030 in-basin projections, it
was determined that the TWP could supply the required additional draft of 450
million m3 per annum at an assurance of between 95 and 98%.
Considering that in-basin requirements have been estimated conservatively, and, with
storage created by two dams proposed as part of the TWP, a surplus of water may
exist between the time that the proposed dams are constructed and 2030.
 
Vaal River Supply Area
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: Major Storage reservoirs |
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: Smaller storage reservoirs |
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: Source & demand basin boundaries |
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: Sub-catchment boundary |
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: Vaal River Catchment |
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: Reservoirs |
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: Subsystem names |
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: Source basins |
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: Demand basins |
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: Vaal River basin |
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: Current transfers |
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: Future transfers |
 
Vaal River Water Demand
Projections
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: LHWP treaty |
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: TR134 most probable |
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: 1999 Reserved Expectation including Water Conservation |
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: March 1997 most probable |
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: Recorded |
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