A study of the natural and anthropogenic impacts on the sediment and water quality of the middle and lower Mvoti River System, KwaZulu-Natal, South Africa.
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This dissertation focussed on the Mvoti River system in KwaZulu-Natal, an important resource for the numerous towns and villages along its course. Catchment activities are varied with agriculture being the predominant activity, and industrial activities common in the lower catchment. The Mvoti River is intensively utilized, especially in its lower reaches, to the extent that it is referred to as a ‘working river’. Modifications of the chemical and physical characteristics of the system, and consequently the biological characteristics, have led to degradation of the system such that the functioning of the lower river has deteriorated in comparison to that of its pre-disturbance condition. There are three main aspects of the Mvoti system around which this dissertation is based, namely, water quality, geochemistry, and conservation of the system. The results of the water quality survey of the estuary revealed that the system is presently experiencing water which is of an inferior quality. Compared against the South African water quality standards, a majority of the parameters exceed acceptable limits and are likely to present negative impacts on aquatic health and potentially human health. Comparison of current results, and water quality data for the system dating back to 1964, revealed that this degradation is not new to the system, and the Mvoti Estuary has in fact been experiencing continued deterioration over the years. The second part of this study investigated heavy metal presence in the sediments of the lower system and elemental presence and distribution in the surface sediments of the middle and lower River respectively. Results indicated that even though selected heavy metals are present, they are of concentrations lower than those of two other South African and two other international systems they were compared with. Enrichment and contamination assessments reveal that contaminants are in all probability present as a result of anthropogenic sources. However, distribution patterns which show highest levels just after effluent disposal sites suggest that the contamination is presumably human-induced and, the predominance of larger grained sediments that do not have high adsorption capacities, suggest that contaminants are readily remobilized into the water column. The final part of this research investigates other environmental problems, and causes, both natural and anthropogenic, experienced by the estuary system. These stresses include poor water quality, reduced water quantity, sedimentation, alien vegetation invasions and loss of biodiversity. Strategies to address these issues are proposed, with the intention of improving the condition of the estuary. This is an attempt at ecological restoration, to restore the estuary to a condition as close to as possible, to its pre-disturbance condition. These strategies include controlling abstraction and discharge, eradicating alien vegetation, controlling sandmining, and improving the overall quality of the system. Also proposed is an estuary management plan (EMP) for the Mvoti system, as there is currently no plan of such a nature in place. The EMP will aid restoration attempts, increase public awareness, and via post-project monitoring and evaluation ensure the success and sustainability of any future projects. Significantly, the adoption of an EMP will be a major step towards the rehabilitation, conservation and protection of this already degraded system.