William John Burchell, multi-skilled polymath

Two hundred and ten years ago, 29-year-old William John Burchell stepped on to the wooden jetty near Cape Town's Castle and immediately started planning his journey of scientific exploration of southern Africa. This would take four years, mostly by ox-wagon, and cover 7000km. On 19 June 1811, he departed Cape Town '’with a mind free from prejudice'’ and “solely for the purpose of acquiring knowledge” …He travelled to about 150 km north of Kuruman, explored the Ky-Gariep (Vaal) River and returned to Cape Town via Graaff-Reinet, the mouth of the Great Fish River, Uitenhage, Mossel Bay and Swellendam...

Quantifying the erosion of the world’s largest impact crater using cosmogenic nuclides: the Vredefort Dome, South Africa.

<p>The world’s largest meteorite impact crater, the Vredefort Dome, has been the subject of extensive studies relating to its age, geology and geomorphology. However, there are no studies pertaining to the rate at which the rocks in the crater remnant are eroding, which can provide insight into the development of the landform over time. This study used the cosmogenic nuclides <sup>10</sup>Be and <sup>26</sup>Al, extracted from purified quartz samples, to investigate erosion rates along the Vaal River as it traverses the impact crater. The Vaal River flows in mixed bedrock-alluvial terrain through the dome, crossing two different bedrock lithologies. The river is multi-channelled (anabranching) atop the granitoids exposed in the core of the dome, then downstream flows as a single channel through a narrow canyon cut into the quartzites that form the rim of the dome. We collected 14 samples from the two rock types to assess lithologic controls on erosion rate and determine landscape erosion history. Results from the analysis of both isotopes were in close agreement; here, we report outcrop erosion rates based on the <sup>10</sup>Be. The average <sup>10</sup>Be-determined erosion rates (± 1 SD)<strong> </strong>along the active river channel for the quartzite (n = 4) and granitoid (n = 6) regions are 1.90 ± 0.12 and 2.19 ± 0.14 m/Ma respectively.  Additional samples from older, now elevated (>5 m) strath terraces developed atop quartzite (n = 4) indicate slightly lower average apparent erosion rates of 1.65 (± 0.09) m/Ma.  The data demonstrate that the erosion rates along the active river channel are similar between the two lithologies despite differences in rock hardness.  The resistant, slowing eroding quartzites serve as the local base level for the river upstream, promoting the development of anabranching, which disperses bedrock erosion over a wider area of the crater. We infer that both bedrock hardness and channel characteristics are important controls on erosion rates along the river.  Collectively, the dataset further illustrates the low bedrock erosion rates that prevail across large areas of the southern African interior.</p>

Impact of Alluvial Diamond Mining on Macroinvertebrate Community Structure in the Lower Vaal River, Northern Cape Province in South Africa

The study aimed to assess the impact of alluvial diamond mining on macroinvertebrate community composition at four selected sites in lower Vaal River in 2016 with the application of the South African Scoring System 5 (SASS5). Macroinvertebrates and physico-chemical water parameters such as pH, turbidity, electrical conductivity and dissolved oxygen were measured seasonally. Turbidity levels were high 5.98.0±0.63 NTU but never exceeded the water quality guidelines of aquaculture, whilst pH values did not vary much and were generally alkaline throughout the study. The macroinvertebrate community structure varied at all sites during the study period. Site 4 was the most impacted site dominated by the more tolerant macroinvertebrates such as Simuliidae, Baetidae and Gyrinidae. The study concludes that although alluvial diamond mining had a negative impact on macroinvertebrate community in the short-term period, they appeared to re-establish quickly once the mining operations stopped.

Integrated assessment of the influence of climate change on current and future intra-annual water availability in the Vaal River catchment

Increasing water demand due to population growth, economic expansion and the need for development puts a strain on the supply capacity of the Vaal River catchment in South Africa. Climate change presents additional challenges in the catchment which supports the country's economic hub, more than 30% of its population and over 70% of its maize production. This study evaluates the influence of climate change on current and future intra-annual water availability and demand using a multi-tiered approach where climate scenarios, hydrological modelling and socio-economic considerations were applied. Results shows exacerbated water supply challenges for the future. Temperature increases of between 0.07 and 5 °C and precipitation reductions ranging from 0.4 to 30% for Representative Concentration Pathways (RCPs) 4.5 and 8.5, respectively, are also predicted by the end of the century. The highest monthly average streamflow reductions (8–10%) are predicted for the summer months beyond 2040. Water Evaluation and Planning (WEAP) simulations project an increase in future water requirements, gaps in future water assurance and highlight limitations in existing management strategies. The study recommends a combination of adaptation plans, climatic/non-climatic stressor monitoring, wastewater-reuse, conservation, demand management and inter-basin transfers to reduce future uncertainty in monthly water sustainability.

Investigating Industrial Effluent Impact on Municipal Wastewater Treatment Plant in Vaal, South Africa

Industrial effluents with high concentrations of toxic heavy metals are of great concern because of their persistence and non-degradability. However, poor operation and maintenance of wastewater treatment infrastructure is a great concern in South Africa. In this study, physico-chemical parameters and heavy metals (HMs) concentration of wastewater from five different industries, Leeuwkuil wastewater treatment plant (WWTP) inflow and effluent, and Vaal River water samples were monitored between January and September 2017, to investigate the correlation between heavy metal pollution and the location of industries and ascertain the effectiveness of the municipal WWTP. Physico-chemical variables such as pH, biological oxygen demand (BOD), dissolved oxygen (DO), chemical oxygen demand (COD), total dissolved solids (TDS) and electrical conductivity (EC) exhibited both temporal and spatial variations with the values significantly higher in the industrial samples. Inductively coupled plasma optical emission spectrometry (ICP-OES) results also showed that aluminium (Al), copper (Cu), lead (Pb) and zinc (Zn) were significantly higher in industrial effluents (p < 0.05), with only Zn and Al exhibiting significant seasonal variability. Statistical correlation analysis revealed a poor correlation between physicochemical parameters and the HMs compositional quality of wastewater. However, toxic HMs (Zn, Cu and Pb) concentrations in treated wastewater from WWTP were above the permissible limits. Although the WWTP was effective in maintaining most of the wastewater parameters within South African Green drop Standards, the higher Cu, Zn, Pb and COD in its final effluent is a concern in terms of Vaal river health and biological diversity. Therefore, we recommend continuous monitoring and maintenance of the WWTPs infrastructure in the study area.