M.Sc. / The Elands River (Incomati System, Mpumalanga) is a biologically diverse and ecologically important riverine system. In terms of the South African National Water Law, the river can be regarded as an aquatic resource, with social, ecological and economical benefits to the local population and the environment itself. The ecological status of the system has, however been questioned, whereby concerns relating to the water quality and the ecological health of the Elands River has been raised. Initially, the concerns focused on an accidental industrial spill of “black liquor” into the Elands River by the Paper Mill at Ngodwana. Subsequently the groundwater in the vicinity of the Ngodwana Mill has possibly been contaminated with chlorides. The contaminated subsurface water has been discharged into the river, and is suspected to be impacting, primarily in the form of increased salinity, the integrity of the Elands River. This study assessed the ecological integrity of a segment of the Elands River between Waterval- Boven and the confluence of the Elands River with the Crocodile River. In addition this study investigated the possibility that increased chloride-based salinity levels were the factors affecting the ecological integrity of the Elands River. The study is divided into three main components. The environmental component involves the assessment of the surface water quality and flow, physical profile, current aquatic habitat status and a biotic integrity assessment of the Elands River and the Crocodile River directly above and below the confluence with the Elands River. An ecotoxicological component incorporated a bioassay of selected chloride-based salts, using daphnids and selected fish species as test organisms. Finally an Ecological Risk Assessment was carried out to evaluate the likelihood that adverse effects were impacting on the Elands River, as a result of the activities of the Ngodwana Mill. The water quality was assessed by implementing the methodology for the determination of present ecological status: water quality, as part of the preliminary determination of the ecological reserve. Historical water quality data were obtained from the Department of Water Affairs and Forestry and from Sappi. During the study, current water quality parameters were obtained from Sappi and parameters were independently sampled. Analyses of the water quality indicated that the Elands River has been subjected to eutrophication and increased levels of chloride-based salinity. Habitat integrity was analysed by constructing two dimensional site transects of the riparian zone and instream channel. Additional habitat indices, the Integrated Habitat Assessment System, the Habitat Cover Ratings and the Site Habitat Integrity system were applied. Habitat results indicate that the in stream habitats of the Elands River are abundant and linked to the flow regime. Additionally the assessments indicated that the habitat makeup of the Elands and Crocodile rivers is primarily riffle, run and rapids habitats, which facilitate the requirements of numerous invertebrate and vertebrate aquatic communities. Biotic assessments studied the integrity of the vegetation, invertebrates and ichthyofaunal communities. The integrity of the vegetation community was assessed by implementing the Riparian Vegetation Index. Results indicated that the riparian vegetation community was modified in varying degrees due to the encroachment of exotic and terrestrial vegetation elements and by anthropogenic activities. The integrity of the invertebrate communities were assessed by implementing the South African Scoring System. Results indicated that the integrity of the invertebrate community was exceptionally high in the vicinity of Hemlock. The invertebrate community structure changed however in areas were a water quality contamination was observed. The ichthyofaunal attributes were assessed by implementing the Fish Assemblages Integrity Index and the Sensitivity Weighted Index of Biotic Integrity. The ichthyofauna assessment revealed two aspects that have conservation importance. These aspects are the occurrence of an endangered species, Chiloglanis bifurcus, and a potentially geologically isolated subspecies of Labeo-barbus polylepis. The index results indicated that the ichthyofauna community structure followed similar trends to the invertebrates by responding to the mentioned stressors. Toxicological assessments were carried out using the standard Daphnid 48-hour LC50 and fish 96-hour LC50 tests. The species selected for the tests were the currently recognized test organisms (Daphnia pulex and Poecilia reticulata) in South Africa. Additional fish species were included in the tests, these species were Oreochromis mossambicus and Clarias gariepinus. Chloride-based salts were selected as the toxicants; these included calcium chloride, magnesium chloride, potassium chloride and sodium chloride. The tests were carried out under controlled conditions using standardised protocols. Results indicated that in excess, chloride-based salinity is toxic to invertebrate and vertebrate organisms. Additionally findings indicated that potassium chloride was the most toxic and sodium chloride the least toxic of the salts. Calcium chloride was selected as the most representative salt to represent salinity. The Ecological Risk Assessment was implemented after international and national frameworks were considered. The assessment was primarily based on the results obtained from the integrity assessment of the Elands and Crocodile rivers. Results obtained indicated that the localised biological template of the Elands River, in the vicinity of the Ngodwana Mill is moderately impacted by the activities of the Mill. The impact is primarily associated with the increased salinity content of the Elands River. Effects of the stressors were modified in relation to a dilution effect. Risks posed by the stressors are deemed to be restricted to a localised area, and it is highly improbable that the stressors would result in the loss of the biotic diversity and thus the ecosystem of the Elands River as a whole. Should the current situation prevail, the intensity and spatial extent or distribution of the stressor could increase. / Dr. V. Wepener
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:12376 |
| Date | 16 October 2008 |
| Creators | O'Brien, Gordon Craig |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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