Mountain catchments are dynamic sedimentary systems where climate variability significantly affects geomorphic processes and sediment connectivity. This study investigates the processes of sediment generation and transfer in the Volcan River basin in central Chile's semi-arid Andes, a region impacted by a prolonged megadrought since 2010. We combined geomorphological mapping, sediment connectivity modelling using the Index of Connectivity (IC), and sediment geochemistry analysis of suspended sediments collected during springsummer season of 2022-2023. Geomorphological mapping identified seven distinct morphogenetic environments (morphostructural, volcanic, glacial, fluvial, denudational, glacial ice and anthropogenic), each contributing variably to sediment transfer. IC analysis revealed spatial heterogeneity in sediment connectivity, with higher values in fluvial and denudational domains and lower values in glacial and volcanic areas. Geochemical analysis of rare earth elements (REE) in suspended sediments indicated that Cenozoic volcanic formations, especially from subglacial sources, are the primary sediment contributors under current hydrological conditions, with Mesozoic units contributing episodically during high-magnitude events like debris flows. Under this scheme, surficial glacial and volcanic morphogenetic domains act as sediment buffers due to their distance to the main fluvial channels as well as morphology that promotes sediment accumulation. In contrast, high melt rates of the glaciers in the valley enhance subglacial connectivity to the fluvial network in the context of the megadrought, while mass wasting events act as sources for short-term sediment pulses during high runoff events. These findings highlight how sediment coupling and provenance in mountain basins are modulated by both the current megadrought and extreme hydrometeorological events. The results provide insights for hazard assessment and sediment management in mountainous regions experiencing climatic stress.