Abstract
M.Sc.
The goal of this study is to determine the relationship between landuse and runoff water quality. The
chosen study area is the Roodeplaat Dam drainage basin. The basin contains three subbasins with varying
characteristics. The western subbasin is that of the Hartbees Spruit with a largely urban character. The
eastern subbasin containing the Edendal Spruit has mostly rural characteristics in terms of landuse. The
central (and largest) sub-basin of the Pienaars River has a mixed (urban/rural) land usage. Specific aims
of the study were the determination of the negative (or positive) influence of urban landuse on the quality
of water that flows into the Roodeplaat Dam, and the determination of the influence of climate (more
specifically precipitation) on this water quality.
A review of different water quality components is provided with the emphasis on those used in the study.
Each of the three subbasins are described in terms of landese to determine the possible influences on
water quality. Water quality data obtained from the Department of Water Affairs (Pretoria) were calculated
to fortnightly averages in order to obtain complete time series. Six inorganic water quality indicators (total
dissolved solids, pH, magnesium, fluoor, sulphate and calcium carbonate) were chosen out of the initial
sixteen obtained. The selection that was made was based on the results of a pre-analysis long term trend
analysis (for a five year period) of the water quality indicators in each of the three sub-basins. Chosen data
sets were compiled to fortnightly and seasonal averages to be used in the analysis phase. The seasons
used were determined by combining precipitation and inflow contributions (to the Roodeplaat Dam) for a
ten year period.
Each of the six chosen water quality indicators were examined in terms of absolute data (fortnightly
averages), seasonal averages and long term trends for the fifteen year study period. Time and spatial
aspects were integrated to make the sinthesis of the study possible.
Albeit some unique conclusions were made, the initial aims of the study could still be reached. It was
determined that urban landuse has a more negative influence on the water quality of the Roodeplaat Dam
drainage basin than rural landuse (in this case mostly small holdings). Apart from this it was shown that
climate (in the form of precipitation) has an even bigger influence on water quality (pollution concentration
levels) in the Roodeplaat Dam drainage basin.