Ph.D. / Female adult specimens of Lamproglena clariae attach to gill filaments of freshwater fish of the family Clariidae, penetrate the gill tissue and consume blood. Previously, studies have been done on the taxonomy of this parasite, but little research has been published on biological aspects. Hence, it was the aim of this study to determine and record L. clariae’s aspects of biology such as ecology, life cycle and pathology. The study was conducted through both field and laboratory observations with specimens collected from the Vaal Dam and Vaal River Barrage. A positive correlation was observed between the host's physical dimensions and the size of the parasite, parasites from both sites preferred the fourth gill and the median part of the gill arch for attachment. There was no significant host gender preference by parasites. Three free living nauplius stages, four copepodite, a cyclopoid and adult stages were recorded as life stages of this parasite. Observations suggested that development of larval stages of L. clariae is influenced by both photoperiod and temperatures. Furthermore low infestation success of the experimental fish was observed. This parasite caused localised infestation as varying degrees of swelling of gill filaments were observed only in the vicinity of its attachment site. Histological examination revealed epithelial hyperplasia, resulting in fusion of gill lamellae and necrosis of the host tissue in the vicinity of the parasite. No correlation exists between the infestation intensity and fish haematocrit values. Although L. clariae causes localized infestation, high intensity of infestation may be detrimental to the fish. Hyperplasia of epithelial tissue resulting in fusion of lamellae would result in restriction of oxygen passage and thus hinder the process of respiration of the host. / Prof. A. Avenant-Oldewage

This study focuses on Acid Mine Drainage (AMD) in the three basins of the Witwatersrand’s goldfields in the Vaal River System in South Africa. AMD has become a highly contested issue. A difference in its definition exists between two groups of role-players identified in the study: government and consultants/activists/NGOs. This study unpacks the differences in the way AMD is defined, the situation of AMD in each of the three basins and the socio-economic implications caused by AMD. A crucial finding was that these definitions determine how the issue is understood and what solutions these role-players propose. The main purpose of the study was to determine whether the South African government’s policy response was appropriate given the socio-economic impacts of AMD and imperatives of sustainable development. This study concluded that, in the policy, there was no clear indication as to what the socio-economic impacts are, and limited attention was therefore given to these impacts. / Development Studies / M.A. (Development Studies)

This study focuses on Acid Mine Drainage (AMD) in the three basins of the Witwatersrand’s goldfields in the Vaal River System in South Africa. AMD has become a highly contested issue. A difference in its definition exists between two groups of role-players identified in the study: government and consultants/activists/NGOs. This study unpacks the differences in the way AMD is defined, the situation of AMD in each of the three basins and the socio-economic implications caused by AMD. A crucial finding was that these definitions determine how the issue is understood and what solutions these role-players propose. The main purpose of the study was to determine whether the South African government’s policy response was appropriate given the socio-economic impacts of AMD and imperatives of sustainable development. This study concluded that, in the policy, there was no clear indication as to what the socio-economic impacts are, and limited attention was therefore given to these impacts. / Development Studies / M.A. (Development Studies)

The use of intestinal parasites as indicators of pollution has increased in Europe due to the fact that parasites accumulate more of the available metals than their hosts. Eighty Largemouth yellowfish, Labeobarbus kimberleyensis (Gilchrist and Thompson, 1913) were collected between April 2005 and February 2006 with gill nets at RAU Island (26° 52, 249’ S, 28 10, 249’ E) in the Vaal Dam. The fish were killed, weighed and their lengths determined. Muscle, liver and spinal cord tissues were collected from each fish and the intestines removed and opened to expose Bothriocephalus acheilognathi. The position of attachment of B. acheilognathi in the host’s intestine was recorded. Thereafter tapeworms were collected in glass bottles and frozen. Water and sediment samples were collected. Clossed vessel microwave digestion was used to digest liver, muscle and tapeworms with Suprapur Nitric acid, and spinal cord tissue with Suprapur Nitric acid and Suprapur Hydrochloric acid. Thereafter metal concentrations of twenty three elements (Lithium, Beryllium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Arsenic, Selenium, Molybdenum, Cadmium, Tin, Antimony, Tellurium, Barium, Mercury, Thallium, Lead and Uranium) were determined specifically for each tissue type with an ICP-MS. Certified dogfish liver (Dolt-3) was used as a quality control standard. Water quality data was provided by Rand Water and included. Statistical data were analyzed with ANOVA and post-hoc tests and parasite infection statistics were calculated. Seasonality and intensity of tapeworms were compared to the intestine and total lengths of the fish. All the tapeworms were identified as the Asian Tapeworm B. acheilognathi Yamaguti, 1934. Bothriocephalus acheilognathi attached between 10% and 20% from the anterior end of host intestine. A 100% prevalence of Asian tapeworm was recorded in all surveys and the highest mean intensity of 231.1 was recorded in autumn and the lowest mean intensity of 73.7 was recorded in summer. The fecundity of largemouth yellowfish was not influenced by the high infection rate of B. acheilognathi as young fish fry was collected during the summer survey and the fish condition was good. No correlation was observed between parasite intensity and total length of each fish. This indicates that intensity is not dependant on host size. Parasite numbers are higher and differ from a previous study. Water quality of Vaal Dam changed in summer, due to transferance of water from the Grootdraai Dam. Algal counts and secchi disk readings increased. This indicates that zooplanktonic intermediate hosts increased due to an increase in food availability and increased the chance of infection. Significant differences were recorded in one sample T-test comparisons, while ANOVA indicated that significant differences between tissue groups and seasons occurred. Bioaccumulation of metals occurred in tapeworms in Selenium, Mercury, and Lead during autumn, Copper, Zinc, Selenium, Cadmium, Antimony, Thallium and Mercury during winter, Lithium, Zinc, Selenium, Cadmium and Antimony during spring and Zinc during summer. The highest mean value was recorded in sediment, followed by water, tapeworms and then the host tissue. The general trend was sediment > water > tapeworms > liver > spinal cord > muscle. Die gebruik van intestinale parasiete as indikatore vir besoedeling het in Europa verhoog omdat die parasiete meer van die beskikbare metale as hul gashere akkumuleer. Tagtig Grootbekgeelvisse Labeobarbus kimberleyensis (Gilchrist en Thompson, 1913) was tussen April 2005 en Februarie 2006 met kieunette te RAU eiland (26° 52, 249’ S, 28 10, 249’ E) in die Vaaldam versamel. Die visse is doodgemaak, geweeg en hul lengtes bepaal. Spier, lewer en werwelkolomweefsel was versamel van elke vis en die intestinums verwyder en oopgemaak om Bothriocephalus acheilognathi bloot te lê. Die posisie van aanhegting van B. acheilognathi in die gasheer se intestinum is aangeteken. Daarna is die lintwurms in glasbottels versamel en gevries. Water en sediment was ook versamel. Geslote-flesmikrogolfvertering was gebruik om lewer, spier en lintwurms met Suprapur® Swaelsuur en werwelkolom met Suprapur® Swaelsuur en Suprapur® Soutsuur te verteer. Daarna is die metaalkonsentrasies van drie-en twintig elemente (Litium, Berillium, Titanium, Vanadium, Chroom, Mangaan, Yster, Kobalt, Nikkel, Kopper, Sink, Arseen, Selenium, Molibdenum, Cadmium, Tin, Antimoon, Tellurium, Barium, Kwik, Tallium, Lood and Uranium) spesifiek vir elke weefseltipe bepaal met ‘n IGP-MS. Gesertifiseerde haailewer (Dolt-3) was gebruik as ‘n standaard ter wille van kwaliteitskontrole. Waterkwaliteitsdata is deur Rand Water verskaf en word ingesluit. Statistiese data was geanaliseer met ANOVA en nagraadse toetse en parasiet infeksie statistieke was bereken. Seisonaliteit en intensiteit van die lintwurms was vergelyk met die totale lengtes van visse en intestinumlengte van die visse. Al die lintwurms was as Asiese lintwurms B. acheilognathi Yamaguti, 1934 geïdentifiseer. Bothriocephalus acheilognathi was tussen 10% en 20% vanaf die anteriorgedeelte van die gasheerintestinum geheg. ‘n 100% persentasiebesmetting was opgeteken in alle opnames met Asiese lintwurms en die hoogste gemiddelde besmettingsintensiteit van 231.1 was opgeteken in die herfs en laagste gemiddelde besmettingsintensiteit van 73.7 waargeneem in die somer. Die broeisukses van die Grootbekgeelvisse was nie beïnvloed deur die hoë infeksies met B. acheilognathi nie, soos blyk uit die feit dat jong vissies versamel is tydens die someropname en die viskondisie was ook goed. Daar was geen korrelasie waargeneem wanneer die parasietintensiteite en totale lengtes van die visse vergelyk is nie. Dit dui dat intensiteit nie afhanklik is van gasheergrootte nie. Die parasietgetalle is hoër en verskil van ‘n vorige studie. Die waterkwaliteit van die Vaaldam het verander gedurende somer a.g.v. die toevoer van water vanaf die Grootdraaidam. Die algtellings en die secchi-skyf lesings het dus verhoog. Dit dui dus aan dat die getal soöplanktoniese tussengashere verhoog het agv die verhoogde voedselbeskikbaarheid en ‘n hoër kans van infeksie vir visse. Betekenisvolle verskille was waargeneem wanneer enkel monster T-toets vergelykings gemaak is, terwyl ANOVA betekenisvolle verskille tussen groepe en seisoene gewys het. Bioakkumulasie van metale in lintwurms het in selenium, kwik en lood gedurende herfs, en in koper, sink, selenium, cadmium, antimoon, tallium en kwik in winter, en in litium, sink, selenium, cadmium en antimoon in lente en in sink gedurende somer voorgekom. Die hoogste gemiddelde waarde was waargeneem in sediment, gevolg deur water, lintwurms en gasheerweefsel. Die algehele akkumulasie verwantskap is sediment > water > lintwurms > lewer > werwelkolom > spier. / Prof. Annemarie Avenant-Oldewage

Per- and polyfluoroalkyl substances (PFASs) are a group of toxic and persistent organic compounds. Their properties make them extremely resistant and they have been shown to have bioaccumulation and toxic properties in the environment and also to biomagnify in both aquatic and terrestrial food webs. This study has analysed different PFASs in African Darter (Anhinga rufa) eggs from five sites along Vaal River; Orange River, South Africa. Sixteen of 23 analysed PFASs were detected and quantified, and the homologue profiles were studied from all five sites. Total perfluorooctane sulfonic acid (PFOS) (all structural isomers) was the predominated compound of all PFASs, accounting for 88-98% for all sites, with a median concentration range of 58 ng/g ww to 2473 ng/g ww. The second highest concentration was found for perfluorodecanoic acid (PFDA) (1.9-42 ng/g ww), followed by perfluorononanoic acid (PFNA) (1.1-14 ng/g ww) and perfluorohexane sulfonate (PFHxS) (0.68-6.0 ng/g ww). The results showed significantly that the three up-stream sites (Welverdiend, Schoemansdrift and Orkney East) had similar patterns and that eggs from Schoemansdrift had the highest levels of PFASs. This may indicate the same source of origin for these three sites and that Schoemansdrift are closest to the contamination source. The three sites (Welverdiend, Schoemansdrift and Orkney East) with similar pattern is closest to Gauteng, which can be where the emission source is located, because it is an industrial area. Perfluoroalkyl carboxylic acids (PFCAs) and PFOS might originate from different sources and the source for PFCAs could be degradation of fluorotelomer-based precursors. Structural isomer profiles of PFOS showed similar results as the PFAS homologue patterns, which give further indication of the source of origin. The contribution of linear PFOS (L-PFOS) to the total amount of PFOS was between the range of 94 and 97%. Bloemhof had the highest concentration of branched isomers among all sites. The L-PFOS concentrations in Bloemhof were also significantly differ from Schoemansdrift. This indicate two different sources between Bloemhof and the three up-steam sites, or an effect of environmental fractionation.

This study is a component of a research project on the economic costs of eutrophication in the Vaal River system. Its objective is to investigate the relationship between raw water quality and the chemical costs of producing potable water at two water treatment plants: Zuikerbosch Station #2 (owned by Rand Water) in the Upper Vaal Water Management Area (UVWMA), and Balkfontein (owned by Sedibeng Water) in the Middle Vaal Water Management Area (MVWMA). Time series data on raw water quality and chemical dosages used to treat raw water were obtained for Zuikerbosch Station #2 (hereafter referred to as Zuikerbosch) for the period November 2004 – October 2006 and for Balkfontein for the period January 2004 to December 2006. Descriptive statistics reveal that raw water in the Vaal River is of a poorer quality at Balkfontein compared to that at Zuikerbosch. Furthermore, the actual real chemical water treatment costs (measured in 2006 ZAR) averaged R89.90 per megalitre at Zuikerbosch and R126.31 at Balkfontein, indicating that the chemical water treatment costs of producing potable water tend to increase as raw water quality declines. Collinearity among water quality (WQ) variables at both water treatment plants was analysed using Principal Component Analysis (PCA). The dimensions of water quality identified in the analysis are similar to those reported in Pieterse and van Vuuren’s (1997) study of the Vaal River. For both water treatment plants, Ordinary Least Squares (OLS) regression was used to identify the relationship between real chemical costs of water treatment and the dimensions of water quality identified through the respective Principal Components Analyses. The estimated regression models account for over 50.2% and 34.7% of variation in real chemical water treatment costs at Zuikerbosch and Balkfontein, respectively. The coefficient estimated for PC1 at Zuikerbosch is statistically significant at the 1% level of probability with high negative loadings of total alkalinity and turbidity. Increases in the levels of total alkalinity and turbidity in raw water treated at Zuikerbosch is negatively related to the chemical costs of water treatment. An increased total alkalinity level was found to reduce the chemical costs of treating potable water. PC2 is statistically the most important variable in the estimated explanatory model for Balkfontein. The estimated regression coefficient for PC2 is statistically significant at the 5% level of probability. The estimated relationship between chemical water treatment costs and PC2 shows that there is a positive relationship between the raw water temperature and chemical water treatment costs. However, increases in the levels of chlorophyll and pH in raw water treated at Balkfontein is negatively related to the chemical costs of water treatment. Total hardness, magnesium, calcium, sulphate, conductivity, and chloride, being the highest positive loadings in PC1, relate negatively to the chemical cost of treating water. For predictive rather than explanatory purposes, a partial adjustment regression model was estimated for each of the two water treatment plants. Using this model, real chemical water treatment costs were specified as a function of real chemical water treatment costs in the previous time period, and of raw water quality variables in the current period. The R2 statistics for the two regression models were 61.4% using the data for Zuikerbosch and 59.9% using the data for Balkfontein, suggesting that both models have reasonable levels of predictive power. The chemical cost of water treatment for Zuikerbosch and Balkfontein are predicted at R96.25 and R90.74 per megalitre per day respectively. If raw water nitrate in the UVWMA increases by 1% per megalitre a day while other factors remain constant, chemical water treatment costs at Zuikerbosch can be expected to increase by 0.297% per megalitre and the cost accompanied this change is (R0.285*1998ML*365days) R207,841.95 provided that Zuikerbosch treats an average of 1998 megalitres per day. Likewise, if Zuikerbosch maintains its daily average operating capacity and is able to maintain an optimal level of total alkalinity in UVWMA, the estimated saving on chemical water treatment cost will be R150.063.78 per annum. At Balkfontein, chemical water treatment cost is expected to increase on average by 0.346% per megalitre per day for a 1% per megalitre per day increase in the level of chlorophyll-a, and the cost accompanied this change is R41,128.20 per annum. The prediction also shows a 2.077% per megalitre per day increase chemical water treatment cost for a 1% increase in turbidity and this accompanied with a chemical water treatment cost of R 249,003 per annum, provided that Balkfontein operates at its full capacity (i.e., 360 megalitres per day). / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: South Africa‟s hydrological and geographical characteristics, coupled with the location of a large part of its mineral endowment, required the development of the complex Vaal River Supply System, including inter-basin water transfer (IBT) projects which have been in operation for over twenty-five years. This research compares the actual water transfers of two such IBTs with their original, appraisal stage, predictions. Transfers are shown to be significantly less and also more variable than predicted. Further research reveals that the state of the receiving system has a large bearing on year-to-year decisions regarding transfers. Past appraisals, following what is called the Incremental Approach, do not adequately consider the likely future inter-basin transfer operating regime. Examination of six case studies, four South African, one Chinese and one Australian, shows that the Incremental Approach is still in general use – despite tools available for an improved approach. A new approach is proposed to upgrade estimations of variable costs associated with water transfers – often substantial life-cycle cost components of IBTs. The generally used unit reference value (URV) measure for appraising and ranking water resource projects in South Africa is also rooted in the economic theory of cost-effectiveness. This shows that the current approach is conceptually flawed; it fails to distinguish between water transfers and effectiveness outputs. The determination of the URV equation is expanded and improved. The upgraded appraisal approach, inclusive of the improved URV methodology, is named the Comprehensive Approach. A step-wise demonstration of the Comprehensive Approach is provided. Uncertainty regarding future water transfers and associated variable costs are provided for by stochastic simulation modelling. Decision analysis theory is applied to obtain the appropriate input value of variable costs. It is shown that the Comprehensive Approach can lead to an outcome significantly different from the Incremental Approach. The research provides new insights, placing water resource planning practitioners in a better position to recommend appropriate IBTs in future. These insights can also be transferred to the design of institutional and financial models related to IBTs, as well as the configuration and operation of supply systems including sea-water desalination projects. / AFRIKAANSE OPSOMMING: Suid-Afrika se hidrologiese en geografiese eienskappe, gekoppel aan die ligging van 'n groot deel van sy minerale bates, het gelei tot die ontwikkeling van die komplekse Vaalrivier Voorsieningstelsel, insluitend tussen-bekken oordragskemas waarvan sommige al vir meer as vyf-en-twintig jaar in werking is. Hierdie navorsing vergelyk die werklike wateroordragte van twee sulke oordragskemas met die oorspronklike vooruitskattings tydens die beplanning-stadium. Daar word getoon dat oordragte noemenswaardig minder en ook meer onreëlmatig was as wat voorspel is. Verdere ondersoek toon dat die stand van die stelsel, aan die ontvangskant, die besluitneming rakende die jaar-tot-jaar oordrag beïnvloed het. Historiese evaluerings het 'n “Inkrementele Benadering” (soos hier genoem) gevolg, wat nie voldoende die toekomstige bedryfsomgewing ten opsigte van tussen-bekken oordragte inagneem nie. Ondersoek van ses gevalstudies, vier Suid-Afrikaans, een Sjinees en een Australies, toon dat die Inkrementele Benadering nog algemeen in gebruik is, ten spyte daarvan dat hulpmiddels vir 'n verbeterde benadering beskikbaar is. 'n Nuwe benadering word voorgestel vir die verbetering van vooruitskattings van veranderlike koste wat met wateroordragte geassosieer word – dikwels 'n aansienlike gedeelte van die lewenssiklus-koste van sodanige skemas. Die Eenheidverwysingswaarde (EVW) maatstaf, wat algemeen in Suid-Afrika gebruik word om waterbronprojekte te beoordeel en in rangorde te plaas, word ook geanker in die ekonomiese teorie van koste-effektiwiteit. Daarmee word getoon dat die huidige gebruik van die EVW konsepsioneel gebrekkig is; dit tref nie 'n onderskeid tussen wateroordragte en effektiwiteitsuitsette nie. Die bepaling van die EVW vergelyking is verbreed en verbeter. Die opgegradeerde benadering, met insluiting van die verbeterde EVW metodiek, word die Omvattende Benadering genoem. 'n Stapsgewyse uiteensetting van die Omvattende Benadering word voorsien. Onsekerhede ten opsigte van wateroordragte en geassosieerde veranderlike koste word deur middel van stogastiese modellering aangespreek. Besluitnemingontledingsteorie word ingespan om die toepaslike insetwaarde van die veranderlike koste te bepaal. Daar word getoon dat die Omvattende Benadering tot 'n resultaat kan lei wat aansienlik verskil van wat met die Inkrementele Benadering verkry word. Die navorsing verskaf nuwe insigte wat die waterbronbeplanner in 'n beter posisie sal plaas om gepaste tussen-bekken oordragskemas voor te stel. Hierdie insigte kan ook oorgedra word na die ontwerp van institusionele en finansiële modelle rakende oordragskemas, asook die uitleg en bedryf van voorsieningstelsels, insluitend seewater-ontsoutingsaanlegte.

The settlement history of the Vredefort Dome can be described as a process of cultural development. The Vaal River hydrosphere, which was for many years a prestigious settlement site, initially attracted large scale game and later livestock farmers. The drifts were a central part of a network of early strategic communication routes and outspans. From 1838, pioneer settlement, farm occupation and agricultural development followed, and the area eventually entered an agriculture-mining era. Gold-mining stimulated the regional economy and also played a significant role in the development of towns in the area. The Vaal River did not play a significant role from a mining perspective, but featured more prominently in the development of villages and, in a sense, served as a political boundary. The location of the water source often determined where people settled permanently. It also decided the position of the house and yard. From the outset, riparian dwellers attempted to manipulate the flow of the river by creating dams and utilising water for irrigation and domestic purposes. Drought conditions also left historical traces; water management projects upstream transformed the Vaal River into a steadily flowing stream, which led to the economic and cultural segregation of north and south. Man's fear associated with drought (too little water), floods (too much water), meteorology (the necessity of water), and the role of the supernatural (divining water) and superstition (the water snake stories) were expressed in the interaction between people and this water environment. A wide variety of people with distinct cultures lived alongside each other in the area. Western and African cultural goods, as well as customs and beliefs, were mutually adopted by these different cultural groups as a result of this contact. The way land has been used in the Dome area has evolved over the years. The culling of game made way for the permanent establishment of the livestocktravelling farmer. Hereafter prolonged drought conditions destroyed pastures and, consequently, large areas of land were ploughed for agricultural use. Agriculture, which is more labour intensive and needs more water for irrigation, was replaced by game farming, which is less labour intensive and requires less water This world heritage site has drawn global interest and ecotourism has attracted visitors to the Vaal River area. The riparian dwellers, however, remain victims of up-stream industrial and sewage pollution; in future, they are likely to fall prey to acid mine water pollution, with disastrous consequences. / PhD (History), North-West University, Vaal Triangle Campus, 2013

The settlement history of the Vredefort Dome can be described as a process of cultural development. The Vaal River hydrosphere, which was for many years a prestigious settlement site, initially attracted large scale game and later livestock farmers. The drifts were a central part of a network of early strategic communication routes and outspans. From 1838, pioneer settlement, farm occupation and agricultural development followed, and the area eventually entered an agriculture-mining era. Gold-mining stimulated the regional economy and also played a significant role in the development of towns in the area. The Vaal River did not play a significant role from a mining perspective, but featured more prominently in the development of villages and, in a sense, served as a political boundary. The location of the water source often determined where people settled permanently. It also decided the position of the house and yard. From the outset, riparian dwellers attempted to manipulate the flow of the river by creating dams and utilising water for irrigation and domestic purposes. Drought conditions also left historical traces; water management projects upstream transformed the Vaal River into a steadily flowing stream, which led to the economic and cultural segregation of north and south. Man's fear associated with drought (too little water), floods (too much water), meteorology (the necessity of water), and the role of the supernatural (divining water) and superstition (the water snake stories) were expressed in the interaction between people and this water environment. A wide variety of people with distinct cultures lived alongside each other in the area. Western and African cultural goods, as well as customs and beliefs, were mutually adopted by these different cultural groups as a result of this contact. The way land has been used in the Dome area has evolved over the years. The culling of game made way for the permanent establishment of the livestocktravelling farmer. Hereafter prolonged drought conditions destroyed pastures and, consequently, large areas of land were ploughed for agricultural use. Agriculture, which is more labour intensive and needs more water for irrigation, was replaced by game farming, which is less labour intensive and requires less water This world heritage site has drawn global interest and ecotourism has attracted visitors to the Vaal River area. The riparian dwellers, however, remain victims of up-stream industrial and sewage pollution; in future, they are likely to fall prey to acid mine water pollution, with disastrous consequences. / PhD (History), North-West University, Vaal Triangle Campus, 2013

Magister Philosophiae (Integrated Water Resource Management) / Rare-infrequent magnitude floods of shorter duration events are significant natural hazards and play a key role in shaping river channel and island geomorphology. For a given river or channel, there is a relationship between the magnitude of a flood, frequency of a flood and duration of a flood, once a flood exceeds a reach-averaged erosional threshold geomorphic change can begin to occur. Expansion of conceptual models for the response of mixed bedrock alluvial influenced dryland rivers to such floods is of increasing scientific importance. The Vaal River near Parys in the Free State Province is characterised by a variable degree of mixed bedrock-alluvial anabranching channels which divide and re-join around the islands. In this study the historical aerial images and flow data from 1938 to 2016 were used to determine the effects of flood dynamics on island geomorphology in a large mixed bedrock-alluvial anabranching river: Vaal River near Parys. The historical aerial images and flow data reveals some minor island geomorphological changes during flood of rare magnitude, infrequent and shorter duration. The highest flood in the record was the one which was found having a recurrence interval of 20-50 years. The changes observed in the mixed bedrock-alluvial anabranching river in the Vaal River near Parys, indicate some minor decrease in the island bar area during flood of rare magnitudes, infrequent and shorter duration with recurrence interval of 20-50 years. The findings in this study area also reveals that the island bars in the area of study shows some degree of stability, however for the past 78 years the islands bar have not change the position. The impact of flood dynamics on island geomorphology in a large, mixed bedrock-alluvial anabranching river is not yet researched in the area of study (Vaal River), these findings will contribute to enhanced analysis of the Vaal River, relatively the impacts of extreme floods in island and channel geomorphology.