Assessment of Meteorological Drought and Wet Conditions Using Two Drought Indices Across KwaZulu-Natal Province, South Africa

Abstract

South Africa has been experiencing a series of droughts for the last few years, limiting the availability of water supply in reservoirs and impacting many sectors of the economy. These droughts have affected even the wetter eastern provinces including KwaZulu-Natal. This paper presents the results of analyses and assessment of meteorological drought across KwaZulu-Natal (KZN) Province of South Africa using two drought indices. The main objective of the study is to understand the changes in rainfall patterns for a period of 48 years (i.e., 1970 to 2017) and identify wet and dry years. The percent of normal precipitation index (PNPI) and rainfall anomaly index (RAI) were used to explore and categorize the wet and dry periods at 18 selected rainfall gauging stations across the province. Mann–Kendall statistics and Sen’s slope were employed on the indices to further understand the trend of drought conditions. The results revealed that 1992 and 2014/15 were the most extremely dry years with 2015 being the driest year over the studied period induced by El Niño. The extremely wet periods were 1987, 1996, and 2000 which have been associated with cyclonic events. Droughts have become more frequent and intense, while wet conditions are less frequent. The drought condition was observed not to be peculiar to one region and to vary from year-to-year. These variations have been associated with global climate drivers including El Niño-southern oscillation (ENSO) and sea surface temperature (SST) conditions. The northern region around Magudu, Hlobane, Vryheid and Dundee were relatively the most affected during periods of extreme drought conditions. Comparative analysis showed that RAI is more robust than PNPI in understanding drought conditions. Thus, it can be applied effectively in Southern Africa in analyzing dry and wet conditions.