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SA now experiencing half-year summers

12 October 2020 | Story Leonie Bolleurs | Photo Supplied

Although several international studies have used temperature metrics to statistically classify their seasonal divisions, a study in which Adriaan van der Walt was involved, would be the first known publication in a South African context using temperature as classification metric.

Gone are the days when we as South Africans would experience a three-month spring season, easing into summer, and then cooling off for three months before we hit winter.

Adriaan van der Walt, Lecturer in the Department of Geography at the University of the Free State (UFS), focuses his research on biometeorology (a specialist discipline exploring the role and climate change in physical and human environments) as well as climatology and geographic information systems.

He recently published an article: ‘Statistical classification of South African seasonal divisions on the basis of daily temperature data’ in the South African Journal of Science.

In this study, which Van der Walt undertook with Jennifer Fitchett, a colleague from the University of the Witwatersrand, data on daily maximum and minimum temperatures was collected from 35 meteorological stations of the South African Weather Service, covering the period between 1980 and 2015.

They went to great lengths to ensure that they had a complete set of data before presenting it to demonstrate seasonal brackets.

First for South Africa

Their statistical seasonal brackets indicate that South Africans now experience longer summers (from October to March), autumn in April and May, winter from June to August, and spring in September.

Although considerable work has been done using rainfall to determine seasonality in Southern Africa, Van der Walt believes that these methods did not work well as there are too many inconsistencies in this approach, as identified by Roffe et al. (2019, South African Geographical Journal). To make matters more complicated – as a semi-arid region, and with desert conditions along the west coast – some regions do not have enough rainfall to use as a classifier.

Temperature, on the other hand, worked well in this study. “Temperature, by contrast, is a continuous variable, and in Southern Africa has sufficient seasonal variation to allow for successful classification,” says Van der Walt.

He continues: “Although several international studies used temperature metrics to statistically classify their seasonal divisions, this study would be the first known publication in a South African context using temperature as classification metric.”

Van der Walt says what we understand as seasons largely relates to phenology – the appearance of blossoms in spring, the colouration and fall of leaves in autumn, and the migration of birds as a few examples. “These phenological shifts are more sensitive to temperature than other climatic variables.”

Seasonal brackets

According to Van der Walt, they believe that a clearly defined and communicated method should be used in defining seasons, rather than just assigning months to seasons.

“One of the most important arguments of our work is that one needs to critically consider breaks in seasons, rather than arbitrarily placing months into seasons, and so we welcome any alternate approaches,” he says.

A number of sectors apply the temperature-based division to their benefit. “For example, in the tourism sector it is becoming increasingly important to align advertising with the season most climatically suitable for tourism,” says Van der Walt.

Temperature-based division is also used to develop adaptive strategies to monitor seasonal changes in temperature under climate change. However, Van der Walt points out that each sector will have its own way of defining seasons. “Seasonal boundaries should nevertheless be clearly communicated with the logic behind them,” he says.

News Archive

Bloemfontein's quality of tap water compares very favourably with bottled water

2009-08-04

The quality of the drinking water of five suburbs in Bloemfontein is at least as good as or better than bottled water. This is the result of a standard and chemical bacterial analysis done by the University of the Free State’s (UFS) Centre for Environmental Management in collaboration with the Institute for Groundwater Studies (IGS).

Five samples were taken from tap water sources in the suburbs of Universitas, Brandwag, Bain’s Vlei, Langenhoven Park and Bayswater and 15 samples were taken of different brands of still and unflavoured bottled water. The samples were analysed at the laboratory of the IGS, while the interpretation of the analysis was done by the Centre for Environmental Management.

“We wanted to evaluate the difference in quality for human consumption between tap water and that of the different brands of bottled water,” said Prof. Maitland Seaman, Head of the Centre for Environmental Management.

“With the exception of two samples produced by multinational companies at their plants in South Africa, the different brands of bottled water used for the study were produced by South African companies, including a local small-scale Bloemfontein producer,” said Prof. Seaman.

According to the labels, the sources of the water vary from pure spring water, to partial reverse osmosis (as an aid to standardise salt, i.e. mineral, content), to only reverse osmosis (to remove salts). (Reverse osmosis is a process in which water is forced under pressure through a pipe with minute pores through which water passes but no – or very low concentrations of – salts pass.)

According to Prof. Seaman, the analysis revealed some interesting findings, such as:

• It is generally accepted that drinking water should have an acceptable level of salt content, as the body needs salts. Most mineral contents were relatively higher in the tap water samples than the bottled water samples and were very much within the acceptable range of drinkable water quality. One of the bottled samples, however, had a very low mineral content, as the water was produced by reverse osmosis, as stated on the bottle. While reverse osmosis is used by various producers, most producers use it as an aid, not as a single method to remove nearly all the salts. Drinking only such water over a prolonged period may probably have a negative effect on the human physiology.

• The pH values of the tap water samples (8,12–8,40) were found to be slightly higher (slightly alkaline), like in all south-eastern Free State rivers (from where the water is sourced) than the pH of most of the bottled water samples, most of which are sourced and/or treated in other areas. Two brands of bottled water were found to have relatively low pH levels (both 4,5, i.e. acidic) as indicated on their bottles and as confirmed by the IGS analysis. The health implication of this range of pH is not significant.

• The analysis showed differences in the mineral content given on the labels of most of the water bottles compared to that found by IGS analysis. The possibility of seasonal fluctuation in content, depending on various factors, is expected and most of the bottling companies also indicate this on their labels. What was a rather interesting finding was that two pairs of bottled water brands claimed exactly the same mineral content but appeared under different brand names and were also priced differently. In each case, one of the pair was a well-known house brand, and the other obviously the original producer. In one of these paired cases, the house brand stated that the water was spring water, while the other (identical) “original” brand stated that it was spring water treated by reverse osmosis and oxygen-enriched.

• Nitrate (NO3) levels were uniformly low except in one bottled sample, suggesting a low (non-threatening) level of organic pollution in the source water. Otherwise, none of the water showed any sign of pollution.

• The bacterial analysis confirmed the absence of any traces of coliforms or E.coli in any of the samples, as was also indicated by the bottling companies. This is very reassuring. What is not known is how all these waters were sterilised, which could be anything from irradiation to chlorine or ozone treatment.

• The price of the different brands of bottled water, each containing 500 ml of still water, ranged between R3,99 and R8,99, with R5,03 being the average price. A comparison between the least expensive and the most expensive bottles of water indicated no significant difference in quality. In fact, discrepancies were observed in the most expensive bottle in that the amount of Calcium (Ca) claimed to be present in it was found to be significantly different from what the analysis indicated (29,6 mg/l versus 0,92 mg/l). The alkalinity (CaCO3 mg/l) indicated on the bottle was also found to differ considerably (83 mg/l versus 9,4 mg/l). The concentration of Total Dissolved Salts (TDS) was not given on the product.

“The preference for bottled water as compared to Bloemfontein’s tap water from a qualitative perspective as well as the price discrepancy is unjustifiable. The environmental footprint of bottled water is also large. Sourcing, treating, bottling, packaging and transporting, to mention but a few of the steps involved in the processing of bottled water, entail a huge carbon footprint, as well as a large water footprint, because it also requires water for treating and rinsing to process bottled water,” said Prof. Seaman.

Media Release
Lacea Loader
Deputy Director: Media Liaison
Tel: 051 401 2584
Cell: 083 645 2454
E-mail: loaderl.stg@ufs.ac.za
3 August 2009

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