Abstract
M.Sc. (Geography)
The Crocodile River drains a highly developed catchment, with 25% of the South African
Gross Domestic Product (GDP) being produced in the Crocodile-West Marico Water
Management Area (WMA). The industrial, agricultural and mining sectors that mostly
contribute to GDP are however greatly dependent on the water resources within the
Crocodile-West Marico WMA and therefore it is important to monitor the status of these
water resources carefully.
This study aimed to determine whether there is a positive correlation between changes in
land-use and changes in water quality in the Crocodile River catchment area across both a
spatial and temporal scale.
Water quality was defined by measurement and analysis of both pure quantitative changes
in water quality parameters as well as qualitative changes in water quality as related to the
end use of the water.
In general water quality in the study area, as measured in terms of the variables used for this
study, was found to still be within acceptable range for domestic use, irrigation, livestock
watering and Industrial Cat. 3 and 4 water uses. The majority of variables were however
above the Aquatic Target Water Quality Range (TWQR). In terms of aquatic ecosystems, the
study area is however not very sensitive with only a few catchments and sub-catchments
classified as freshwater ecosystem priority areas. The freshwater ecosystem priority areas
are also located in mostly the upper catchment where water quality is generally fair to good
i.e. as confirmed by water quality results from Water Monitoring Stations (WMS) 90195 and
90165.
It was confirmed that spatial and temporal changes in land use had a definite impact on
physical and chemical water quality as measured at each WMS. The variables used to
determine water quality changes due to land use change were however not ideal to
determine certain land use impacts. Urban, industrial and mining impacts would for example
have been easier to identify by means of metal and heavy metal concentrations as well as
other toxic organic and inorganic constituents. To this extent it was a challenge to link
specific industries or industrial areas to water quality changes. This was mostly due to the
fact that industrial processes differ vastly, with a range of pollutants being emitted and
discharged into the environment.
It was however evident from the results that nutrient enrichment mostly originates from point
sources, specifically Wastewater Treatment Works (WwTWs), and that salinization is mostly
caused by intensive crop irrigation. Build-up or urban areas mostly resulted in lower levels of
salts and dissolved solids, possibly due to limited exposed ground surfaces. It was further
found that mining related to Platinum Group Metals (PGMs) resulted in and increase
chloride, dissolved major salts, electrical conductivity, total hardness, potassium,
magnesium, sodium and sulphate concentrations...