6 February 2018

Drought in South Africa caused by El Niño, human action and climate change

Niko Wanders

“Cape Town could run out of water in April”, “Fears grow that taps will run dry”. These are just two of the headlines that appeared in January. Satellite images confirm that the water situation in the region is serious. Drought expert dr Niko Wanders blames this on the lack of rain caused by the strong El Niño of recent years. The situation has been further exacerbated by climate change and the increased demand for water in the region. ​

The present drought in Cape Town has been caused by extremely poor rainfall in recent months, with the result that the water supplies are under enormous pressure. It is feared that, unless it rains very soon, the drinking water supply in Cape town will be seriously threatened. Of course, rain in itself will not immediately solve the problem, as the water supplies have shrunk to such an extent that it will take a long time for them to be replenished.

Figure 1: Satellite image of the reservoirs surrounding Cape Town in the month of January for the last four years. It is clear that the amount of water in the region has decreased markedly during this period (image: NASA)

Strong El Niño

“The most important cause of the lack of rain is thought to be the strong El Niño of recent years”, says drought expert Niko Wanders of Utrecht University. He shows that the amount of available water in the region around Cape Town is indeed dependent on El Niño (Figure 2). Wanders: “The stronger the El Niño signal, the less water is available in the region. This is first manifest in the form of less rain, soon followed by lower discharges in the rivers. These lower discharges also have a direct influence on water storage levels in the reservoirs. If there is a continuous shortage of water feeding the reservoirs, this will inevitably lead to water shortages and thus drought. This drought can have terrible consequences, as Cape Town is now experiencing.”

Figure 2: Correlation between the El Niño signal and discharge anomalies. The red colours indicate a high risk of drought, while blue indicates a high risk of flooding.

Effect of climate change

Unfortunately, the situation is not being helped by climate change, as the duration and intensity of drought is only set to increase in the coming years (Figure 3). Measures such as new reservoirs or better irrigation systems could help to mitigate the water scarcity, thinks Wanders.

Human influence

Human influence on drought is also an increasingly important factor, and this present drought is no exception. Across the continent of Africa, more and more water is being used for irrigation, and this puts increasing pressure on the limited water available. During times of drought this becomes increasingly evident, and it also means that existing shortages become worse. This is true in other parts of the world besides Africa, so sustainable water consumption is one of the most important factors if we want to overcome drought in the future. We need to invest in sustainable measures to ensure that water is not lost or too polluted for use as drinking water.

Figure 3: Changes in duration and intensity of drought in the 21st century. The red colours indicate an increased probability of droughts, while green indicates a probable decrease in droughts in some areas.