An integrated study of the Isipingo River and Estuary : water and sediment quality, estuary-nearshore material fluxes, anthropogenic impacts and management.
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Date
2013
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Abstract
The Isipingo River and Estuary system located in the province of KwaZulu-Natal, although
relatively small, has been subjected to the impacts of intense development within the
catchment. The catchment is characterized by informal and formal dwellings and intensive
industrial activities in the lower catchment and in close proximity to the estuary. Significant
modifications to the hydrology of the system has occurred as a result of the diversion of the
Umlazi River (which previously merged with the Isipingo River at the estuary mouth),
canalization of the lower portion of the Isipingo River flowing through the Prospecton
Industrial Area and the development of the Diversion Works system (to regulate flows to the
lower Isipingo River), removal of riparian vegetation, encroachment onto the river and
estuarine floodplain, and land reclamation through the infilling of wetlands all of which has
culminated in a deterioration of the functionality and health of this system. The main aspects
of this study focus on water and sediment quality, material flux between the estuary and the
sea and the management of the system. The water quality variables covered as part of this
dissertation include physical, chemical (nutrients and heavy metals) and microbiological
(faecal coliforms) components. The water quality of the river and estuary presents a risk to
human health and the concentrations of heavy metals generally exceeded the South African
Water Quality Guidelines that prescribes target levels, implying potential negative impacts to
aquatic health. The Isipingo system exhibited signs of eutrophication with phosphorus
concentrations in excess of the target level to prevent eutrophication. Excessive water
hyacinth growth was visible during most of the field surveys. A geochemical assessment of
heavy metals in surface sediments of the river and estuary was also undertaken. The results
indicate that although the presence of several metals were undetectable at certain river
sites, the concentrations of those heavy metals present increased in a longitudinal direction
from the river to the estuary. The contamination factor analysis for all metals indicated low
contamination except for selenium. The riverine sites yielded moderate enrichment by some
heavy metals in both seasons. The degree of contamination for each site with the exclusion
of selenium was low. The inclusion of selenium in the assessment raises the estuary to a
considerably contaminated status in the wet season. The analysis suggests that the
enrichment of the system by selenium is due to an anthropogenic source. The Geo-accumulation
Index places the sediment in an overall unpolluted category. The study
conducted on the net exchange of heavy metals and nutrients between the Isipingo Estuary
and the adjacent marine environment (i.e. Indian Ocean) demonstrates that significant
quantities of the suite of heavy metal analysed are exported on an annual basis while
copper, nickel and zinc are imported into the estuary. Significant quantities of ammonia and
nitrates are exported annually from the Isipingo Estuary while a net annual import of phosphorous is observed. The variation in the quantity and concentration of nutrients
exported during the seasons may be attributed to anthropogenic source. The import of
nutrients from marine sources can accumulate in the estuary and contribute to
eutrophication of the Isipingo Estuary. This study also demonstrated that although the ebb
flow has a much longer duration than the flood flow, the flood velocities observed were
generally greater than the ebb velocities. The final part of this research identifies other
environmental problems experienced in the Isipingo catchment. The following issues are
identified as directly or indirectly contributing to stress and deterioration of the water quality
of the Isipingo system: reduction in water quantity, poor water quality, moderate enriched
sediment, loss of habitat integrity, species diversity and invasive alien vegetation and
uncontrolled solid waste. A Water Quality Management Plan including management
objectives, strategies and action plans to address the direct and indirect factors influencing
the system are proposed. A water quality monitoring program is also proposed for the
Isipingo River and Estuary. The adoption and execution of the water quality management plan and monitoring program will assist in the prevention of further degradation of the system and will be a stepping stone toward improvement.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2013.
Keywords
Pollutants--KwaZulu-Natal--Isipingo., Water quality management--KwaZulu-Natal--Isipingo., Estuaries--KwaZulu-Natal--Isipingo., Water quality--KwaZulu-Natal--Isipingo., Theses--Environmental science., Isipingo River and Estuary (KwaZulu-Natal), Isipingo River (KwaZulu-Natal)