Vaal_Barrage_Dam=The Vaal Barrage was finally completed in 1923. Spanning the Vaal River over a distance of about 400 m, it was as Professor Tempelhoff describes it "a veritable monument of engineering skill." More than 275 000 m³ had been excavated in rock of which 43 000 m³ had been cast in concrete.
<p>By making use of the Duff Abrams method of steel-reinforced concrete the structure was strong and capable of withstanding all types of flooding conditions. It was constructed in a blend of art nouveau and classical styles. There were 36 sluice gates creating a storage capacity of nearly 70 Mm³ of water.</p>
<p>The Vaal Barrage is a ‘hotspot’area with the highest levels of pollution (i.e. high bacteria, algae, heavy metals, salts and nutrients) in the mainstream of the Vaal River. The highest risk is Eutrophication - where excess nutriets that stimulate excessive plant growth (algae, periphyton attached algae, and nuisance plants weeds) is received.This enhanced plant growth, often called an algal bloom, reduces dissolved oxygen in the water when dead plant material decomposes and can cause other organisms to die.</p>
Image: DWAF (South Africa)