A dissertation submitted to the Faculty of Science in fulfilment of the requirements for the
degree of Master of Science
November 2015, Johannesburg / South Africa is faced with water quantity and quality issues in most catchments. Intensification of
coal-based industrial activity in the Waterberg, Limpopo and the concomitant emissions of oxides of
nitrogen (NOX) and sulphur (SOX) pose potential ecological impacts to regional freshwater systems.
Some research indicates that a significant proportion of minerals in the Waterberg parent rock may be
prone to acid generation with catchment soils being potentially susceptible to acidification via NOX
and SOX deposition. Cultural and recurrent nutrient loading of freshwater bodies also impacts on
primary production and can ultimately alter the natural structure and functioning of these ecosystems.
Trend analyses on historical hydrological data from 1982 to 2013 were carried out for several response
water quality variables from six quaternary Waterberg catchments. Results were assessed for possible
changes attributable to increased NOX and SOX loading post commencement of large-scale coal
combustion. Historical inorganic N:P ratios were calculated in conjunction with a series of nutrient (N
and P) bioassay experiments to predict which nutrient may be limiting growth of stream periphyton.
Although trends were identified in most catchments for several of the water quality variables, the
notion that the onset of large scale coal combustion has led to noticeable downward trends in pH and
upward trends in either inorganic N or sulphate is not unequivocal. Patterns in trends were not distinct
for catchments situated in close proximity to the primary emission source and those further away. Nor
were there any distinct differences in trends between upwind and downwind catchments. Climate and
geo-hydrological factors are likely to still function as the primary drivers of spatial and temporal
variation in past and present catchment water quality.
Contrary to the view that stream primary production is limited largely by the availability of P,
predictions based on N:P ratios calculated in this study suggest N to be the limiting nutrient. This was
shown to be the case in four of the five study-site rivers. N-limitation increased by 18% (67% to 85%)
in the Matlabas River post-commencement of large-scale coal combustion. A greater increase of 24%
(60% to 84%) was observed in the Middle Mokolo. Although cultural eutrophication levels in the
Waterberg do not yet exceed management-set targets, the cumulative effect of industrial-derived
nutrient inputs remains a threat to the nearshore marine ecosystem and human communities living
downstream.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/19345 |
| Date | 20 January 2016 |
| Creators | Burne, Craig |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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