Blue, Green and Mean

15 November 2015
Blue, Green and Mean Image : 2106

With South Africa finding itself in the grip of a searing heat wave, and water sources running dry, the reality of water pollution and harmful blue-green algae is becoming a more worrying reality.


Blue-green algae (or cyanobacteria) is a toxic bacteria that grows in warmer, nutrient-rich water. The bacteria ends up depleting the water of oxygen and releasing several toxins that could pose serious health risks to humans and animals.

According to a study by the South African Journal of Science in May this year, South Africa has the highest known levels of blue-green algae contamination in the world. About two thirds of our national resource is contaminated, and that figure will grow.


Between 2002 and 2012, 62% of 50 analysed water bodies contained high levels of blue-green algae. Of the 50 bodies of water, 26 were found to pose a high health risk due to surface scum (a toxic layer or film on the water surface). However, a handful of water bodies are worse off than the rest, with almost 30% of the water surface covered in scum.

  • Barberspan Dam >45%

  • Hartbeespoort Dam >45%

  • Koppies Dam >45%

  • Spitskop Dam ±30%

  • Vaal Dam ±30%

  • Lake Chrissiesmeer ±30%

Such high levels of contamination are an immediate concern with regard to drinking water, agricultural and recreational water use.

A number of reservoirs are also showing high levels of algae contamination.

  • Mthatha Dam

  • Ncora Dam

  • Erfenis Dam

  • Krugerdrift Dam

  • Ntshingwayo Dam

  • Allemanskraal Dam

It has been estimated that 18 of 25 major river catchments are also contaminated.


Currently, there isn’t an effective treatment method available. Water treatment plants use a filtering process to remove most of the blue-green algae from supplied water before they reach our taps. However, there isn’t a large-scale treatment method to treat entire bodies of water at once.

Fortunately, there are other ways to prevent and/or limit blue-green algae:

  • Improve the management of wastewater disposal systems.

  • Regulate pollution caused by fertilisers from the agricultural sector more efficiently.

  • Educate yourself and know how to identify contaminated water.

Be sure to read part 2 on blue-green algae and find out how you can protect yourself and the health symptoms to look out for.