Evidence of increasing water scarcity due to frequent drought under SSP2-4.5 climate change scenario in the Western Cape Province, South Africa

Abstract

Prolonged droughts can create severe water scarcity that can negatively affect sustainable human-environment interactions. In the Western Cape Province (WCP), South Africa, prolonged drought episodes are aggravating water scarcity and adversely affecting agricultural production. This study aimed to explore water resources sustainability in agroecological zones (AEZs) of the WC province. To this end, historical (1991–2020) and future (2021–2050) precipitation datasets under the SSP2-4.5 climate scenario were obtained from the sixth version of Model for Interdisciplinary Research on Climate, (MIROC6). Using the Reliability (R_el.) − Resilience (R_es.) − Vulnerability (V_ul.) framework and Standardized Precipitation Index (SPI), the sustainability index (SI) was used to quantify water availability conditions in different AEZs using the geometric mean method. The Mann-Kendall (M-K) test was applied to investigate the trends at a significance level of p < 0.05. The findings show that between 2021 and 2050 under the SSP2-4.5 climate scenario drought conditions will exacerbate water scarcity in AEZs compared to the historical observations. The results indicate that in arid climates, future SI, exhibited moderate water shortage (0.60 < SI < 0.80), while in semiarid climates future SI values, exhibited mild water shortages (0.62 < SI < 0.71); while in the humid climates, future SI values projected normal to above normal water availability condition (0.52 < SI < 0.58). Overall, trend analysis indicated non-insignificant positive vulnerability trends and significant negative trends for both reliability and resilience indicator. This study provides policy interventions and can foster development pathways to attaining the Sustainable Development Goals from a water and climate action perspective.