Groundwater quality monitoring around Bass Lake, Betty's Bay, South Africa

The study involves the analysis of groundwater around Bass Lake, part of a fragile black water lake system situated along a narrow coastal plain in the southern Cape, in order to establish the quality of the water and to identify the sources of pollution. The study was conducted in 1998 during the winter season in which water samples were taken from Bass Lake and from eight well-points surrounding the lake. The samples were analysed for traces of faecal pollution, nutrient concentrations, pH and conductivity. The results of these tests showed that the water is relatively uncontaminated during the winter season. Only slight contamination was found at one sampling site. However there was enough secondary evidence to suggest that the lake had being reasonably polluted at various times of the year. This evidence was in the form of medical reports, changes in the natural vegetation and incidences of algal blooms. It is expected that significant contamination only occurs during the summer time, when the visitor occupancy rate in the surrounding houses is high and consequently there is an increase in the volume of waste water and sewage received by domestic sewage systems. The study suggests that water monitoring methodology used in this study should yield better results during the drier summer period when there is decrease in the rate of groundwater flow and a lower water table. Monitoring throughout the year is recommended. Keywords: groundwater quality; septic tanks; sewage pollution (Afr J Aqua Sci: 2000 25(1)