Abstract
Global impacts of drought conditions pose a major challenge towards the achievement of the 2030 Sustainable Development Goals. As a result, a clarion call for nations to take actions aimed at mitigating the adverse negative effects, managing key natural resources and strengthening socioeconomic development can never be overemphasized. The present study evaluated hydrological drought conditions in three Cape provinces (Eastern, Western and Northern Cape) of South Africa, based on the Standardized Streamflow Index (SSI) calculated at 3- and 6-month accumulation periods from streamflow data spanning over the 3.5 decades. The SSI features were quantified by assessing the corresponding annual trends computed by using the Modified Mann–Kendall test. Drought conditions were also characterized in terms of the duration and severity across the three Cape provinces. The return levels of drought duration (DD) and drought severity (DS) associated with 2-, 5-, 10-, 20- and 50-year periods were estimated based on the generalized extreme value (GEV) distribution. The results indicate that hydrological drought conditions have become more frequent and yet exhibit spatial contrasts throughout the study region during the analyzed period. To this end, there is compelling evidence that DD and DS have increased over time in the three Cape provinces. Return levels analysis across the studied periods also indicate that DD and DS are expected to be predominant across the three Cape provinces, becoming more prolonged and severe during the extended periods (e.g., 20- and 50-year). The results of the present study (a) contribute to the scientific discourse of drought monitoring, forecasting and prediction and (b) provide practical insights on the nature of drought occurrences in the region. Consequently, the study provides the basis for policy- and decision-making in support of preparedness for and adaptation to the drought risks in the water-linked sectors and robust water resource management. Based on the results reported in this study, it is recommended that water agencies and the government should be more proactive in searching for better strategies to improve water resources management and drought mitigation in the region.
Highlights
Drought is a naturally recurring hazard associated with a decrease in water availability over time within a region
The Standardized Streamflow Index (SSI) computed from 3.5 decades of streamflow data was used to evaluate hydrological drought conditions in the southwestern and southeastern parts of South Africa, covering the WC, NC and episodes include the 1991–1996 (EC) provinces
Hydrological drought analysis based on the SSI for 3- and 6-months accumulation periods indicate that most of the study regions experienced pronounced, yet localized drought conditions during the studied period
Summary
Drought is a naturally recurring hazard associated with a decrease in water availability over time within a region. Such conditions are often attributed to anomalous weather conditions associated with the decreasing intensity or a deficiency of precipitation; the changes in the onset and cessation of precipitation; and in climatological parameters, such as temperature, relative humidity and evapotranspiration [1,2,3]. The southwestern and southeastern regions of the country, the Western, Eastern and Northern Cape provinces, have been experiencing diverse impacts of drought, resulting from the common classified categories (e.g., meteorological, agricultural, hydrological and socioeconomic) conditions [8,9]. Severe drought in the Northern Cape province has affected farming activities and cost the provincial government millions of Rands in drought-related funding relief to mitigate the inherent effects
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