The causes of Cape Town’s water crisis are hotly contested. There is a drought, of course. But there are also other reasons brought up in the public discourse, particularly on social media, such as population and water demand growth, unreported agricultural use, invasive species sucking out water in catchments, poor planning and mismanagement of water supply system, and lack of foresight in development of new water sources. Are these significant contributors to the shortage? It’s very difficult to say without dedicated, comprehensive analyses. But facts are few, opinions plenty.
Few people question whether there is a drought: what is questioned is its severity. This has important implications. If the drought has been mild, then it should not have resulted in a major water crisis. If it has been severe, then it has just been a bad ticket on the climate lottery, and all the other factors would be at most aggravating factors but not the main cause. The issue is obviously socially tense, creating wedges between authorities and citizens, between those who institute water restrictions and those who have to bear the brunt of them.
In this article I look at the most up-to-date rainfall data to assess how severe the current drought is. I have tried to answer that question before. But that article was based on very limited data, and was carried out well before 2017’s rainy season had finished. Now I have a more comprehensive dataset, which provides an opportunity to perform a more robust assessment.
There are a number of stations that measure rainfall in the vicinity of the Western Cape Water Supply System (WCWSS) dams. Data for them are available from the Department of Water and Sanitation (DWS) website.
Not all stations in this dataset have good records; there are numerous gaps. It appears that nine stations have data available for recent years, but four are located in the region of the WCWSS dams, and have no significant gaps or systematic errors from 1981 through 2017. Those stations are: Vogel Vallij, Zacharashoek, Theewaterskloof and Kogel Baai.