A Comparison of Water Quality and Ecotoxicity between Von Bach, Swakoppoort and Goreangab Dams

This study focused on assessing physical (temperature, pH, turbidity and conductivity), chemical parameters (nitrates and phosphates), algal toxicity (Anatoxin-a and Microcystin-LR) of the water as well as the potential toxicity of water towards zooplankton. This was done in an attempt to evaluate the suitability of water from Goreangab, Swakopppoort and Von Bach dams for anthropogenic use and its potential in supporting biodiversity. Three sampling stations were selected from each dam to obtain a representative view of water quality at different places in each dam. Sampling points were selected close to the inflow, at the dam walls and in the middle of the dam. No significant difference was found in Anatoxin-a concentration in the three dams, but Microcystin levels differed significantly between the dams. Swakoppoort Dam had the highest concentration (0.5 µg/L) and Von Bach Dam had the lowest concentration (0.44 µg/L) of free Microcystins. The toxicity towards zooplankton also differed significantly between the three dams; lethal concentration at 25% effluent strength (LC25) was calculated after 24h (Von Bach Dam at 40% effluent strength and Goreangab Dam at 22% effluent strength) and LC50, after 48h (Von Bach Dam at 85% effluent strength and Goreangab Dam at 37 % effluent strength) . This study concluded that the three dams could support biodiversity to some level, but anthropogenic use is only allowed after water has been treated.