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Article

Hydrological Drought Assessment Based on the Standardized Streamflow Index: A Case Study of the Three Cape Provinces of South Africa

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South African Weather Service, Private Bag X097, Pretoria 0001, South Africa
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Department of Geography, Geoinformatics and Meteorology, University of Pretoria, Private Bag X020, Hatfield, Pretoria 0028, South Africa
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Department of Information Technology, Central University of Technology, Free State, Private Bag X200539, Bloemfontein 9300, South Africa
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Centre for Transformative Agricultural and Food Systems, School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Pietermaritzburg 3209, South Africa
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School of Geography and Environmental Science, University of KwaZulu-Natal, Durban 4041, South Africa
*
Authors to whom correspondence should be addressed.
Academic Editor: Alina Barbulescu
Water 2021, 13(24), 3498; https://doi.org/10.3390/w13243498
Received: 9 November 2021 / Revised: 2 December 2021 / Accepted: 4 December 2021 / Published: 8 December 2021
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. View Full-Text
Keywords: hydrological drought; water resources; mitigation; streamflow; return levels; trends; GEV distribution hydrological drought; water resources; mitigation; streamflow; return levels; trends; GEV distribution
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MDPI and ACS Style

Botai, C.M.; Botai, J.O.; de Wit, J.P.; Ncongwane, K.P.; Murambadoro, M.; Barasa, P.M.; Adeola, A.M. Hydrological Drought Assessment Based on the Standardized Streamflow Index: A Case Study of the Three Cape Provinces of South Africa. Water 2021, 13, 3498. https://doi.org/10.3390/w13243498

AMA Style

Botai CM, Botai JO, de Wit JP, Ncongwane KP, Murambadoro M, Barasa PM, Adeola AM. Hydrological Drought Assessment Based on the Standardized Streamflow Index: A Case Study of the Three Cape Provinces of South Africa. Water. 2021; 13(24):3498. https://doi.org/10.3390/w13243498

Chicago/Turabian Style

Botai, Christina M., Joel O. Botai, Jaco P. de Wit, Katlego P. Ncongwane, Miriam Murambadoro, Paul M. Barasa, and Abiodun M. Adeola. 2021. "Hydrological Drought Assessment Based on the Standardized Streamflow Index: A Case Study of the Three Cape Provinces of South Africa" Water 13, no. 24: 3498. https://doi.org/10.3390/w13243498

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