Exploring variability of drought events for the western region of South Africa

Abstract

The occurrence of drought in South Africa is inevitable, as it is a naturally occurring phenomenon. What makes this phenomenon extreme is its creeping nature, which could unravel into prolonged, socio-economic drought. Socio-economic drought imposes the greatest threat to agriculture and the economy. Examples of this type of drought recently (at the time of this study) occurred in the Northern Cape, Western Cape, North West, Free State, and Eastern Cape provinces. Most of these provinces were declared disaster regions because of prolonged drought and/or underwent socio-economic impacts. Parts of these provinces are located in the western region of South Africa, which is the area of interest in this study due to its dry nature. The standardised precipitation evapotranspiration index (SPEI) was used to analyse the potential changes in the drought frequency, duration, and intensity of district municipalities. Those findings were linked to potential changes in vegetation, by examining the normalized difference vegetation index (NDVI) trends. The SPEI was then used to examine future drought events from 2050-2100 using Coupled Model Intercomparison Project (CMIP6) data, which was compared to the data from 1962-2022. The 1962-2022 findings showed that the frequency, duration, and intensity of drought had worsened in all district municipalities in the second half of the study period. During the extensive drought period of 2012-2022, a decrease in the NDVI values is present. Yet, the NDVI trends showed an overall increase in all five provinces, meaning that the worsened drought conditions, observed in the SPEI, did not reflect on the NDVI to the same degree. Only 4/17 district municipalities are predicted to have worsened drought conditions in 2050-2100 in comparison to the 1962-2022 results. Overall, this study provides insight into the intensities, frequencies, and duration of past and future drought events in the district municipalities. This information can enable stakeholders, policymakers, mayors, etc. of the district municipalities to proactively prepare for worsening drought conditions.