Assessment of Climate-Induced Drought Dynamics in the Semi-Arid Nzhelele River Catchment, Limpopo, South Africa

Climate-induced drought increasingly threatens water security in semi-arid regions, as rising temperatures become the primary driver of hydro-climatic variability. This study assessed long-term drought dynamics in the Nzhelele River Catchment (NRC), through Mann–Kendall (MK) trend analysis, Sen’s slope estimation, and the Standardized Precipitation Evapotranspiration Index (SPEI) for the period from October 1994 to September 2024. Aggregated in situ weather station data and 0.25° × 0.25° gridded climate node (GCN) datasets were used to quantify trends in mean annual temperature, potential evapotranspiration (PET), and precipitation. The results revealed a statistically significant warming trend of 0.037 °C/yr. and an increase in PET at an average of 6.343 mm/yr., while precipitation showed a weak, non-significant decline (–0.568 mm/yr.). SPEI analysis identified recurrent severe droughts between 2003 and 2009; 2010–2013; 2014–2016; and 2018–2020, with the 2014–2016 period as the most extreme climatic stress. Gridded SPEI aligns closely with station-derived SPEI across all accumulation scales (R2 = 0.76–0.87; p-value < 0.001), supporting the use of ERA5-based climate products for drought monitoring in data-scarce regions. Due to the limited number of in situ stations and spatial averaging inherent in gridded datasets, the results provide an approximate representation of hydro-climatic conditions across the catchment. Overall, the findings indicate a shift toward temperature-driven drought regimes, growing climate risks to water availability, and the need for climate-resilient water resource planning.