Theme unsuitability is noted to have inhibited the accuracy of groundwater potential zones (GWPZs) mapping approach, especially in a semi-arid environment where surface water supply is inadequate. This work, therefore presents a geoscience approach for mapping high-precision GWPZs peculiar to the semi-arid area, using Buffalo catchment, Eastern Cape, South Africa, as a case study. Maps of surficial-lithology, lineament-density, drainage-density, rainfall-distribution, normalized-difference-vegetation-index, topographic-wetness-index, land use/land cover, and land-surface-temperature were produced. These were overlaid based on analytical hierarchical process weightage prioritization at a constituency ratio of 0.087. The model categorizes GWPZs into the good (187 km2), moderate (338 km2), fair (406 km2), poor (185 km2), and very poor (121 km2) zones. The model validation using borehole yield through on the coefficient of determination (R2 = 0.901) and correlation (R = 0.949) indicates a significant replication of ground situation (p value < 0.001). The analysis corroboration shows that the groundwater is mainly hosted by a fractured aquifer where the GWPZs is either good (9.3 l/s) or moderate (5.5 l/s). The overall result indicates that the model approach is reliable and can be adopted for a reliable characterization of GWPZs in any semi-arid/arid environment.
The complexity of streamflow processes inhibits significant information about catchment performance and its sensitivity to climate change. Little is known about the severity of climate change within the coastal area of the monsoon–subtropical zone of climatic transition. This study advances a quasi-local scale analysis to simplify daily streamflow dynamics and their relationship with monthly hydro-climatic series (1981–2020) using six gauging stations on the Buffalo River due to its socio-economic significance. An integrated framework based on continuous wavelet transform (CWT), wavelet coherence (WC), innovative trend analysis (ITA), Mann–Kendall (MK), Sequential Mann–Kendall, and Pettitt tests were employed. CWT showed huge declivity in daily streamflow intensity (7676 to 719), >100 mm/day streamflow frequency (15 to 0), and wetness spell time-gap. WC obtained significant streamflow–rainfall co-movement of 8–196-month periodicities, which characterized Buffalo as anti-phase (1–4-month), lag-lead (8–32-month), and in-phase (64–196-month) in processes. The Buffalo River’s sensitivity to significantly decreasing rainfall trends and increasing temperature trends depicts Streamflow–ENSO teleconnection. Contrarily, ITA and MK exhibited significantly increasing trends of tributaries’ low flow and inferred the perennial status of the catchment. The Pettitt test corroborates the deductions and asserts 1990 (temperature), 1996 (streamflow), and 2004/2013 (rainfall) as the abrupt change points, while SMK captured a critical streamflow slump in 2015–2020. Overall, the study proved the reductionist approach and model framework to achieve the hydrological process simplification and resolution of hotspots of hydrologic extremes within a bimodal climate with complex topography. This study remarks on the management policy of the BR and provides a reference for managing water resources and catchment hydro-climatic extremes.
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