Reconstructing droughts and wetter periods in the Leandra area, South Africa
Hi All. It’s David Nash here from the University of Brighton. I’m a physical geographer with interests in historical rainfall variability in southern Africa, working with Angie Hart and the rest of the team on the GCRF drought project in Leandra. My job, alongside my colleague Clare Kelso from the University of Johannesburg, is to build up a historical timeline of all the droughts and wetter periods that have affected Gauteng and southern Mpumalanga provinces (our broad study area) since records began. That way we can understand the relative severity of the drought that affected the Leandra area during the summer rainy season of 2015-2016 in its full historical context.
If we were working on a project of this type for the UK, all we would need to do is contact the Met Office to obtain their relevant rainfall data. However, the availability of records is very different in southern Africa. Some places, such as Cape Town, have lengthy instrumental rainfall and temperature datasets, extending back as far as the 1840s. However, for much of South Africa, meteorological information has only been collected since the early 20th century.
Our first goal was to try to assemble all of the available instrumental rainfall data for the region to see how long a record we could reconstruct. The South African Weather Service were incredibly helpful in this respect. They provided the project with monthly rainfall data for 29 meteorological stations distributed across our study area, the earliest of which was from 1889 (for central Johannesburg). To analyse the records, we first had to check for missing data and for any possible errors in recording. We then ran various statistical analyses, to allow us to construct the graph of average rainfall variability shown below.
This graph may look complicated, but it is quite straightforward to interpret if you focus on the areas shaded in gold. These highlight the periods of severe drought that have occurred since the late 19th century. Fortunately, most of these droughts spanned only a single summer rainy season. As a result, communities were more likely to have been able to cope with the drier conditions – droughts are a fairly regular feature of life in South Africa. However, we can identify seven occasions when severe drought extended over two rainy seasons – the summers of 1891-93, 1904-06, 1912-14, 1981-83, 1991-93, 2001-03 and 2015-16. These sorts of droughts are likely to have been much more problematic for communities, as they create longer term impacts on food and water availability.
The graph also provides some important context for our study. It shows that rainfall levels during the most recent drought period ranked 118th out of 128 years of record – in other words, the summer of 2015-2016 was the 11th driest since meteorological records begin for the region. By any measure, this was a particularly severe drought for Leandra!
The second area of the project that Clare and I have been working on is the identification of droughts and wetter episodes for time periods before rainfall records begin. To do this, we have been exploring various collections of documents from the mid-to late 19th century stored in libraries and archives in Johannesburg and Pretoria. We tend to think that the British are obsessed with the weather, but from what we have read during the course of this investigation, I can confirm that this obsession is global!
We were fortunate enough to be able to access full runs of the very earliest newspapers from the study area. These include now defunct titles such as the Transvaal Advertiser (you can see me reading this on microfilm below), and the Diggers’ News, a weekly paper summarising news from the first gold mining areas in what was to become Johannesburg. We were also able to read the full runs of the Eastern Star, the forerunner of The Star, one of the most widely read newspapers in South Africa today.
Historical newspapers are a particularly rich source of information about weather variability in the past, especially where the weather had an impact on agriculture, on buildings and roads, or on communication between urban areas. Newspaper entries regularly described the general weather, particularly during the months of September and October prior to the expected start of the summer rainy season. They also provide extremely detailed accounts of extreme events such as droughts and heavy rainfall. The image below shows one entry from the Transvaal Advertiserfrom 29th March 1884, describing the general weather conditions and the state of the pasture (the veld) at the time. From these sorts of accounts, we can build up a picture of the changing weather conditions during a rainy season, assess how relative levels of rainfall varied, and can explore the impacts of climate variability upon human livelihoods.
During the course of our research in Johannesburg and Pretoria we collected over 800 individual quotations about the weather and related environmental conditions from historical newspapers. We have now entered all of the details into a dedicated database and are beginning to explore the results. The next time I blog, it will hopefully be to provide you with more detail about the patterns historical climate variability that we are able to identify.
If you want to know a more about this part of our study, feel free to e-mail me:Â [email protected]
