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FLOOD OPERATION OF VAAL DAM IN T

VIEWS: 103 PAGES: 19

									FLOOD MANAGEMENT




                          •By: Joyce Mathole


            •Directorate: Hydrological Service
     •Department of Water Affairs and Forestry
    FLOOD MANAGEMENT OPERATION IN THE
        VAAL / ORANGE RIVER SYSTEM

• Management of both minor and major floods in the
  Vaal / Orange River System is done by the Directorate
  Hydrological Service of the Department of Water
  Affairs and Forestry. The “Flood Room” in Pretoria
  serves as an information centre to collect, process and
  distribute rainfall, stage and flow data

• Normal operation of the individual dams in the system
  is the responsibility of the Departmental Regional
  Offices
     The main objectives of flood
  management in order of priority are:-

• To ensure the safety of the structures.

• To minimise the damages.

• To ensure that the dams are 100% full at the
  end of each flood.
                         Vaal Dam

•Located in the Vaal River 65 km upstream of the town
Vereeniging




               •Equipped with 60 crest gates
               •Discharge of one gate at FSL: ~ 105 m3/s
               •Capacity of dam: 2 603 mil m3
               •Catchment area of dam: 38 505 km2
                Vaal / Orange River System
Vaal/ Orange System covers about 49% the size of
the RSA, excluding Lesotho




Vaal and Bloemhof Dams are the only dams equipped with spillway
gates - some control possible
           Data for the NWSRFS



• Rainfall Data (South African Weather
  Service)

• Real Time Flow stations (DWAF)
SAWS: Satellite Data
Radar Data
Rain Gauge Data
Spatial interpolation and mapping of rainfall
  Real time data collection points in the Vaal /
             Orange River System




52 gauging stations collecting near real time flow and / or rainfall
data - available on the Hydrology real time web site
Liebenbergsvlei River at Frederiksdal
               Uses of Data

• Rainfall data: Input to Rainfall/Runoff
  models (Kovacs/Sacramento)
• Real Time Flow Data: Input to routing
  model (Muskingum)
• Weather forecast: Information for dam
  operation
• Above Info: Flood Management
  Routing times in Vaal / Orange System (days)




Flood warnings can provide time for people to take action
to protect their property as well as allowing emergency
services to prepare and plan for evacuations and other
emergency actions
 Overview of the 1988 major flood in the Vaal /
            Orange River System




Spitskop Dam in the Harts River and Tierpoort Dam in
the Riet River failed during the early stages of the rainfall
event
Spitskop dam
    1988
THE END

								
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