A baseline limnological study of Wagendrift Dam (Thukela basin, KwaZulu-Natal)

Abstract

Basic features of the physical and biological limnology of Wagendrift Dam, a moderately large impoundment on the Boesmans River, were studied between July 1989 and May 1990. This man-made lake showed a typical monomictic pattern of summer stratification (November through April) and holomictic winter circulation (May to October). Water quality was chemically good (Department of Water Affairs and Forestry records), with little evidence of nutrient enrichment. Water clarity during the study was moderately low (mean SD and K d PAR values of 0.45 mand 2.55 m-1), with little evidence of persistent mineral turbidity, suggesting reasonably satisfactory catchment conditions. In keeping with the low nutrient status, surface chlorophyll content remained below 5 μg ·l - 1 throughout the study. In terms of ecological groupings, the phytoplankton was numerically dominated mostly by ‘Competitive’ green algae for most of the year. ‘Stress-tolerant’ cyanophytes were continuously sparse, but were marginally more abundant during summer stratification.

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