Quantifying Intra-Catchment Streamflow Processes and Response to Climate Change within a Climatic Transitional Zone: A Case Study of Buffalo Catchment, Eastern Cape, South Africa

The complexity of streamflow processes inhibits significant information about catchment performance and its sensitivity to climate change. Little is known the severity change within coastal area monsoon–subtropical zone climatic transition. This study advances a quasi-local scale analysis simplify daily dynamics their relationship with monthly hydro-climatic series (1981–2020) using six gauging stations on Buffalo River due socio-economic significance. An integrated framework based continuous wavelet transform (CWT), coherence (WC), innovative trend (ITA), Mann–Kendall (MK), Sequential Mann–Kendall, Pettitt tests were employed. CWT showed huge declivity in intensity (7676 719), >100 mm/day frequency (15 0), wetness spell time-gap. WC obtained streamflow–rainfall co-movement 8–196-month periodicities, which characterized as anti-phase (1–4-month), lag-lead (8–32-month), in-phase (64–196-month) processes. River’s significantly decreasing rainfall trends increasing temperature depicts Streamflow–ENSO teleconnection. Contrarily, ITA MK exhibited tributaries’ low flow inferred perennial status catchment. test corroborates deductions asserts 1990 (temperature), 1996 (streamflow), 2004/2013 (rainfall) abrupt points, while SMK captured critical slump 2015–2020. Overall, proved reductionist approach model achieve hydrological process simplification resolution hotspots hydrologic extremes bimodal complex topography. remarks management policy BR provides reference for managing water resources extremes.