1887

n Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie - Rol van Lesotho-Hooglandwater op Vaalrivieralge : oorspronklike navorsing

Volume 32, Issue 1
  • ISSN : 0254-3486
  • E-ISSN: 2222-4173
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Abstract

Die Vaalrivier is, met verloop van tyd, tot so 'n mate verryk deur voedingstowwe dat algopbloeie tans probleme skep. 'n Unieke geleentheid om te bepaal of daar veranderinge in die waterchemie en algsamestelling in die Vaalrivier voorgekom het, het hom voorgedoen nadat oligomesotrofe Katsedamwater (Lesotho) ingevoer is om in die toenemende wateraanvraag in die Vaalrivieropvangsgebied te voorsien. Die konsentrasie en samestelling van alge in die Vaalrivier is tydens die periodes tussen 1992 en 1994, tussen 1998 en 2000, asook 2004 en 2006 vergelyk met dié in die Katsedam tussen 1998 en 2006. Sekere algspesies, wat aanvanklik afwesig was in die Vaalrivier, het ná die oordrag van Lesothowater voorgekom. 'n Gemengde algpopulasie wat in die Vaalrivier gevind is voordat Katsedamwater oorgedra is, het ná die oordrag geleidelik verander na 'n populasie wat gedomineer is deur sianobakterieë. Die totale algkonsentrasie in die Vaalrivierbarrage het verdubbel van die periode tussen 1992 en 1994 tot dié tussen 2004 en 2006 wat aandui dat die oordrag van helder, oligomesotrofe Katsedamwater die eutrofe Vaalrivierwater nie genoegsaam verdun het om die algkonsentrasie te laat afneem nie. Resultate toon aan dat stroomaf-besoedeling en eutrofikasie in die Vaalriviersisteem die verdunningseffek van Katsedamwater uitgeskakel het. Dit het tot veranderinge in die algsamestelling en -konsentrasie, kenmerkend van toenemende eutrofikasie, in die Vaalrivier gelei.


The Vaal River has become so nutrient-enriched that algal blooms pose problems. A unique opportunity arose to determine if there were changes in the chemistry en algal composition of the Vaal River after oligomesotrophic Katse Dam (Lesotho) water was imported to augment supplies in the light of growing water demands in the Vaal River catchment area. Algal concentration and composition in the Vaal River during three periods (between 1992 and 1994, 1998 and 2000, as well as 2004 and 2006) were compared to those in the Katse Dam (1998-2006). Some algal species, initially absent from the Vaal River, appeared in the river during and after transfer. Mixed algal assemblages found in the Vaal River before transfer of Katse Dam water gradually changed after transfer to assemblages mainly composed of cyanobacteria. The total algal concentration in the Vaal River Barrage doubled from the period between 1992 and 1994 to that between 2004 and 2006, indicating that the transfer of clear, oligomesotrophic Katse Dam water did not dilute the eutrophic Vaal River water sufficiently in order to reduce algal concentrations. Results showed that continuous downstream pollution and eutrophication of the Vaal River system eliminated the diluting effect of Katse imports. This resulted in changes in algal composition and concentration in the Vaal, characteristic of those associated with increasing eutrophication.

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/content/aknat/32/1/EJC131455
2013-01-01
2020-08-14

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