THE SUMMER CONDITION OF THREE EASTERN TRANSVAAL RESERVOIRS AND SOME CONSIDERATIONS REGARDING THE ASSESSMENT OF TROPHIC STATUS

Abstract

Summer temperature, oxygen and light penetration profiles in the Da Gama, Klipkopje and Witklip Reservoirs are presented. Analysis of waters from different depths showed the presence of chemical stratification despite the absence of clear thermal stratification. An algal bioassay procedure also confirmed the presence of increasing quantities of available nutrients with depth in all three reservoirs. The significance of the results in assessing trophic status is discussed and it is concluded that for South African impoundments, an anaerobic hypolimnion is not exclusively associated with eutrophy.