Vaal Basin Research Articles

Tsallis Entropy for Assessing Spatial Uncertainty Associated with Mean Annual Runoff of Quaternary Catchments of the Middle Vaal Basin in South Africa.

This study assesses mainly the uncertainty of the mean annual runoff (MAR) for quaternary catchments (QCs) considered as metastable nonextensive systems (from Tsalllis entropy) in the Middle Vaal catchment. The study is applied to the surface water resources (WR) of the South Africa 1990 (WR90), 2005 (WR2005) and 2012 (WR2012) data sets. The q-information index (from the Tsalllis entropy) is used here as a deviation indicator for the spatial evolution of uncertainty for the different QCs, using the Shannon entropy as a baseline. It enables the determination of a (virtual) convergence point, zone of positive and negative uncertainty deviation, zone of null deviation and chaotic zone for each data set. Such a determination is not possible on the basis of the Shannon entropy alone as a measure for the MAR uncertainty of QCs, i.e., when they are viewed as extensive systems. Finally, the spatial distributions for the zones of the q-uncertainty deviation (gain or loss in information) of the MAR are derived and lead to iso q-uncertainty deviation maps.

Shannon Entropy for Measuring Spatial Complexity Associated with Mean Annual Runoff of Tertiary Catchments of the Middle Vaal Basin in South Africa.

This study evaluates essentially mean annual runoff (MAR) information gain/loss for tertiary catchments (TCs) in the Middle Vaal basin. Data sets from surface water resources (WR) of South Africa 1990 (WR90), 2005 (WR2005) and 2012 (WR2012) referred in this study as hydrological phases, are used in this evaluation. The spatial complexity level or information redundancy associated with MAR of TCs is derived as well as the relative change in entropy of TCs between hydrological phases. Redundancy and relative change in entropy are shown to coincide under specific conditions. Finally, the spatial distributions of MAR iso-information transmission (i.e., gain or loss) and MAR iso-information redundancy are established for the Middle Vaal basin.

Class frequency distribution for a surface raw water quality index in the Vaal Basin

A harmonised in-stream water quality guideline was constructed to develop a water quality index for the Upper and Middle Vaal Water Management Areas, in the Vaal basin of South Africa. The study area consisted of 12 water quality monitoring points; V1, S1, B1, S4, K9, T1, R2, L1, V7, V9, V12, and V17. These points are part of a Water Board’s extensive catchment monitoring network but were re-labelled for this paper. The harmonised guideline was made up of 5 classes for NH4+, Cl-, EC, DO, pH, F-, NO3-, PO43- and SO42- against in-stream water quality objectives for ideal catchment background limits. Ideal catchment background values for Vaal Dam sub-catchment represented Class 1 (best quality water), while those for Vaal Barrage, Blesbok/Suikerbosrand Rivers and Klip River represented Classes 2, 3 and 4, respectively. Values above those of Klip River ideal catchment background represented Class 5. For each monitoring point, secondary raw data for the 9 parameters were cubic-interpolated to 2 526 days from 1 January 2003 to 30 November 2009 (7 years). The IF-THEN-ELSE function then sub-classified the data from 1 to 5 while the daily index was calculated as a median of that day’s sub-classes. Histograms were constructed in order to distribute the indices among the 5 classes of the harmonised guideline. Points V1 and S1 were ranked as best quality water (Class 1), with percentage class frequencies of 91% and 60%, respectively. L1 ranked Class 3 (34%) while V7 (54%), V9 (53%), V12 (66%) and V17 (46%) ranked poorly as Class 4. B1 (76%), S4 (53%), K9 (41%), T1 (53%) and R2 (61%) ranked as worst quality (Class 5). The harmonised in-stream water quality guideline resulted in class frequency distributions. The surface raw water quality index system managed to compare quality variation among the 12 points which were located in different sub-catchments of the study area. These results provided a basis to trade pollution among upstream-downstream users, over a timeframe of 7 years. Models could consequently be developed to reflect, for example, quality-sensitive differential tariffs, among other index uses. The indices could also be incorporated into potable water treatment cost models in order for the costs to reflect raw water quality variability.Keywords: class frequency distribution; cubic interpolation; harmonised in-stream water quality guideline; ideal catchment background; Vaal basin; water quality index

Raw water quality weight factors: Vaal basin, South Africa

Weight factors (WFs) were developed for surface raw water pollution indicator variables in Vaal River's Upper and Middle Vaal sub-basins, in South Africa. The overall objective was to formulate a quantifiable ranking system to indicate importance of pollutant variables given their established effects on human and environmental health. Multi-criteria decision analysis (MCDA) was applied to qualitative data that were obtained from South Africa's target water quality ranges as well as from literature which represented expert opinion. The human and environmental health effect choice sets were ranked from 1 to 5 on nine pollutant variable criteria: NH3/NH4+, Cl-, conductivity (EC), dissolved oxygen (DO), pH, F-, NO3-/NO2-, PO4(3-) and SO4(2-). The weighted-sum method (WSM) then assigned highest and lowest normalised weights (NWs) to F- and Cl-, respectively, for human health effects (ɛhh) alternative. Highest and lowest NWs were assigned to NH3/NH4+ and EC, respectively, for environmental health effects (ɛeh) alternative. After aggregating the ɛhh and ɛeh WFs, resultant values ranked the variables from highest to lowest as follows: F->NO3-/NO2->/NH3/NH4+>DO>pH>SO4(2-)>PO4(3-)>EC>Cl-. The results represented the importance of variables given their established effects on human and environmental health. It was concluded that WFs provided a quantifiable barometer which could signal harmful exposure to elucidate negative effects of using polluted surface raw water in the study area. The values could be incorporated into water quality models like water quality indices. The approach could be used to develop WFs for other sites, taking into account issues like the site's pollution variables of concern as well as using a ranking key constructed from established literature.

Towards a more sustainable surface raw water tariff structure in the Vaal basin : a situational analysis

With an increasingly urbanised population, further study was necessary to determine if water could be used more efficiently by applying efficient tariff structures in combination with decision support tools in the form of models. This paper highlighted challenges towards establishing a sustainable surface raw water tariff structure. Limitations of using the pollute-pays principle for setting a surface raw water tariff structure within a highly urbanised environment were noted. A tariff structure in the Upper and Middle Vaal Water management Areas which are part of the Vaal basin in South Africa was shown to promote inequity such that a downstream user paid more for using more polluted water. Recommendations specific to the Vaal basin included adopting a user-pays principle and also use of a model that incorporated variability in surface raw water quality for tariff setting and also for purposes of predicting potable water treatment costs. Key words: Polluter-pays principle, sustainable tariff structure, urbanised population, user-pays principle, Vaal basin.

Canteen Koppie at Barkly West: South Africa's first diamond mine

Canteen Koppie, a national monument of historical value, occurs next to Barkly West on the north bank of the Vaal River. Diamonds were discovered there in 1869 and it became the first alluvial diamond diggings in South Africa. The digging continued, albeit on and off in the years leading up to 1948 when the site was proclaimed a national monument. The sediments occur in a structurally controlled and glacially modified depression within the andesitic lavas of the Archaean Ventersdorp Supergroup. The fluvial gravels were deposited, and locally mixed with the colluvium, in the downstream end of a palaeo-loop of the Vaal River as a splay deposit where the channel abruptly widens as it exits this narrow loop. The gravel accumulation has been described as the 12 m to 16 m terrace package linked to the Younger Gravels of the Vaal Basin and correlated with the Pleistocene Rietputs Formation. There are two gravel facies associations and one sand facies within the splay unit. Colluvial facies are dominant particularly in the upper part and are composed of large andesite fragments which are mostly sub-angular and lacking obvious abrasion features suggesting that these are of local derivation. The gravel of the fluvial facies are crudely cross-bedded and consist of small to medium sized exotic sub-rounded pebbles that have been mixed with the local andesite boulders in the toes of the scree deposits. These facies are more prominent in the lower part of the succession. The red sand facies occurs as thin cover particularly in the distal part of the gravel units and increases in thickness in the lee of the gravel splay. The exotic clasts in the fluvial gravel are derived from the palaeo-Vaal, erosion of nearby Dwyka sediments which can still be found along the north bank of the loop, and by reworking of higher level and older gravels, remnants of which are still present on top of the hill at Canteen Koppie. The input of the coarse andesite clasts is linked to scree slope deposits fed by exfoliation of local bedrock from this hill. The upward coarsening trend of this infill reflects the gradual abandonment of the loop by the palaeo-Vaal and its inability to remove the coarse colluvium during those latter stages of its occupation of this palaeo-loop. A climatic change to more arid periods might have had some influence. Canteen Koppie has also produced an abundance of Acheulian Stone Age artefacts. These are present in both sedimentary facies suggesting that this splay deposit is at least Late Pliocene to Lower and Middle Pleistocene in age. Recent dating of the overlying sands indicates that these are at least 125 000 years old. Finally an analysis of the mining records suggests that this splay deposit might have produced between 10 000 carats and 15 000 carats of diamonds which would have expressed itself in the region of three to five carats per hundred tonnes. The oversize clasts of the scree deposits would have acted as important traps for the diamonds.

Fluid characteristics of the diamondiferous Droogeveldt Gravels, Vaal Valley, South Africa

The Late Cretaceous to early Tertiary Droogeveldt gravels, one of the more famous alluvial diamond diggings in the Vaal basin of South Africa for both grade and large stone size, were totally exploited in the earlier part of this century. The best recoveries were obtained from high elevation (1,100- to 1,130-m elev) bimodal gravels situated in narrow (2- to 20-m wide), straight-sided, bedrock depressions <1 km long, some 5 to 10 km from the current Vaal River (1,000-m elev). These gravels, forming a fining-upward profile, comprise cobble to pebble, silica-rich clasts characteristic of the current Vaal drainage basin set among now-weathered bedrock boulders derived locally from the underlying Archean Ventersdorp volcanic rocks. The gravel-filled depressions, known by the early mining community as sluits, coincide with major structural lineaments in the Ventersdorp bedrock. Although the now rare, remnant weathered profiles resemble colluvium or debris flow-type deposits, the presence of potholed and smooth, polished, but irregular bedrock footwall in the sluits as well as rounded and percussion-scarred silica clasts points to a more energetic fluvial influence. The well-jointed bedrock sidewalls of the sluits provided readily accessible boulders (oversize clasts) to these gully-like features. Thus, the exceptional diamond concentrations and large stone size in the Droogeveldt gravels are attributed to a combination of primary, fixed turbulent zones formed by the narrow bedrock gullies with attendant pothole and scour trapsites, and secondary, quasi-fixed turbulent zones associated with the locally derived boulders (oversize clasts) in a paleo-Vaal River drainage. The sluits are not eroded kimberlite dikes and the bulk of their diamonds are likely to be sourced from the Cretaceous kimberlites in the greater Kimberley area.

Revised strength factor for coal in the Vaal Basin : van der Merwe, J N J S Afr Inst Min MetallV93, N3, March 1993, P71–77

The South African coal-mining industry uses a uniform safety-factor formula for non-squat pillars, incorporating a coal-strength constant that was derived empirically by Salamon and Munro in the 1960s. The constant is 7,2 MPa. Since that time, collapses of pillars at relatively high safety factors have occurred in the Vaal Basin. Analysis of the post-1960s' collapses indicated that the strength constant for the Vaal Basin is 4,5 MPa. A crude method for the prediction of the minimum life span of pillars in the Vaal Basin is presented.

Mineralisation Problems in the PWV Complex – The Identification of Viable Solutions by Means of a Suite of Mathematical Models

The Pretoria-Witwatersrand-Vereeniging (PWV) complex, the most economically active region in southern Africa, depends for its water supply upon the Vaal river, which serves also as the sink for much of the pollution emanating from the complex. Over the past 45 years, the annual increase in water demand by the urban consumers has exceeded 7%, and the current rate of growth shows no sign of diminishing. The region is not richly endowed with waer resources and already considerable quantities of water have to be transferred into the Vaal basin from the adjacent Tugela basin. Mineral pollutant loads, both from point and from diffuse sources, have risen to intolerable levels. With the onset of the rainy season, there is a pronounced “first flush” phenomenon, whereby salts accumulated in the catchment are washed off, causing unacceptably high TDS peaks in the primary water supply source. The problem is compounded by the feed-back effect whereby effluents are recycled into supply with consequent build- up of salinity. Without some form of numerical model it would not have been reasonably possible to plan measures to improve the position. A suite of numerical models having meteorological data as basic input has been developed. The models simulate at key points in the system, for any demand horizon, monthly or daily salt concentrations associated with a wide variety of alternative management strategies. The models have been successfully calibrated and verified. Incorporated in the models are the economic parameters relating salinity in the water supply to the costs incurred by consumers in having to use water of poor quality. A method has been evolved whereby the costs and benefits to consumers resulting from various water resources and pollution control planning and management options can be objectively compared. Both present-day and probable levels of future pollution and of demand are taken into account in the evaluation of options.

BOOK REVIEWS

Book reviewed in this article: Geography and Geographers: Anglo‐American Human Geography since 1945. K. J. Johriston. Strukturierung eines Verkehrsnetzes. Christoph Leiistrionn “The Haitian Problem”: Illegal Migration to the Bahamas. Dir ww I. Mur.shdl. The History of Topographical Maps: Symbols, Pictures and Surveys. P. D. A. Harvey. Geography and the Urban Environment. Volume III, Progress in Research and Applications. D. T. Herbert iind R. J. Johnston (Eds.) The Port of New York: A History of the Rail and Terminal System from the Beginnings to Pennsylvania Station. Crrrl W. Conilit. Man and Environmental Processes. K. J. Gregory und D. E. Wulling (Eds.). A River of Diamonds: An Alluvial History of the Lower Vaal Basin, South Africa. David M. Helgren. Geomorphological Processes. E. Drrhvshire, K. J. Gregorv, and J. R. Hails. Chemical Foundations: The Alkali Industry in Britain to 1926. Kenneth Wnrren. The Development of the U.S. Urban System. Volume I. Concepts, Structure, Regional Shifts. Edgar S. Dunn, Jr. Population Growth and Urban Systems Development: A Case Study. G. A. van der Knaap. Planning Industrial Development. David F. Walker (Ed.). Center and Periphery: Spatial Variation in Politics. Jean Gottmann (Ed.). An Historical Geography of Europe, 1500–1840. N. J. G. pounds.

Rivers of diamonds. An alluvial history of the Lower Vaal Basin, South Africa. David M. Helgren. University of Chicago, Department of Geography Research Paper No. 185, 389 pp., 1979, paperback $8.00.

Rivers of diamonds. An alluvial history of the Lower Vaal Basin, South Africa. David M. Helgren. University of Chicago, Department of Geography Research Paper No. 185, 389 pp., 1979, paperback $8.00.

Evolution of landforms in South Africa

Book reviewed in this article:David M. Helgren: Rivers of Diamonds. An Alluvial History of rhe Lower Vaal Basin, South Africa

River of diamonds — an alluvial history of the Lower Vaal Basin, South Africa

River of diamonds — an alluvial history of the Lower Vaal Basin, South Africa

Late Cenozoic paleoclimates of the Gaap Escarpment, Kalahari margin, South Africa

The Gaap Escarpment is a dolomite cuesta demarcating the southeast margin of the Kalahari. Since Miocene-Pliocene times, thick masses of lime tufa have repeatedly accumulated at several points along this escarpment, and four regional sequences are described. These allow discrimination of six major depositional complexes, commonly characterized by basal cryoclastic breccias or coarse conglomerates that reflect frost shattering and torrential runoff, followed by sheets and lobes of tufa generated in an environment substantially wetter than today. A chronostratigraphy for the last 30,000 yr is provided by 14C dating, with direct or indirect correlations to the Vaal River sequence. The regional stratigraphy as well as faunal dating indicate an early Pleistocene age for Australopithecus africanus at Taung. Repeated episodes of protracted cold or wetter climate or both begin in terminal Miocene times, and the last Pleistocene cold-moist interval began after 35,000 yr B.P. and ended 14,000 yr B.P. Early and late Holocene times were mainly wetter, whereas the middle Holocene was drier than today. The paleoclimatic sequence differs from that of the southern and southwestern Cape or that of East Africa, but close parallels are evident throughout the lower Vaal Basin and the southern Kalahari. The tufa cycles provide a unique, 5,000,000-yr record of climatic variation in the Kalahari.summer-rainfall belt that can be related to complex anomalies of the general atmospheric circulation.

Acheulian settlement along the Lower Vaal river, South Africa

Artifact occurrences from the alluvial fills of the Lower Vaal Basin, South Africa, are summarized with reference to a revised stratigraphic framework for these deposits. The Older Gravels, Younger Gravels, and the Riverton Formation record the history of Cenozoic denudation in this region and demonstrate repeated climatic fluctuations both moister and drier than the semi-arid present. The settlement geography and geology of eight important Acheulian stone-tool collections from the Younger Gravels and lower Riverton Formation are described. These occurrences, known as Homestead, Larsen, Riverview VI, Newman's Pont, Canteen Koppie, Pniel, Power's Site, and Muirton, indicate Acheulian settlement on low terraces next to the main river, in channelways during low flow periods, and on low, rocky slopes adjacent to the floodplains.

The Oppermansdrif Dam Archaeological Project: Vaal Basin

The Oppermansdrif Dam Archaeological Project: Vaal Basin

Hydrologic aspects of limnology in South Africa

Because of the variability of rainfall and lack of extensive groundwater resources, concentrations of population in South Africa give rise to the need for river regulation projects. The inter-related effects on inland waters of regulation by storage and of degradation as a result of use by man are examined. Particular attention is paid to the Vaal basin, the water resources of which are currently being exploited to the direct advantage of its six million inhabitants.

The Archaeology of the Earliest Superficial Deposits in the Lower Vaal Basin Near Holpan, Windsorton District

(1967). The Archaeology of the Earliest Superficial Deposits in the Lower Vaal Basin Near Holpan, Windsorton District. South African Geographical Journal: Vol. 49, No. 1, pp. 39-56.