Spatial Separation of Water and Sediment Sources and Its Anthropogenic Amplification: Process Shifts in the Upper Yellow River

ABSTRACT In intensively managed river basins, anthropogenic activities are increasingly overriding natural climatic drivers in controlling water and sediment fluxes, leading to fundamental shifts in hydrological processes. Focusing on the heavily engineered Upper Yellow River, this study analyses 6 decades (1960–2022) of data to quantify how anthropogenic interventions have reconfigured these fluxes. We identified two pivotal transition years (1968, 1986) linked to major reservoir impoundments, after which anthropogenic activities accounted for 74.7%–90.7% of the runoff decline and 85.8%–93.4% of the drastic sediment loss. This dominance was achieved primarily through large reservoirs, which trapped sediment and homogenised flow regimes, and widespread soil conservation structures (e.g., check dams), which disconnected hillslope sediment sources from channels. These interventions not only reduced fluxes but also amplified a pre‐existing natural pattern: Three headwater tributaries contributed > 90% of the runoff but < 42% of the sediment, whereas four mid‐basin tributaries supplied 85%–90% of the sediment load. Based on sub‐basin responses, we further classified sediment regimes into three process‐based types: Interception‐dominated, supply‐enhanced and competition‐modulated. By quantitatively linking human actions to specific alterations in key hydrological and geomorphic processes, including sediment connectivity and water partitioning, this work provides a diagnostic framework for understanding how anthropogenic engineering cascades through hydrological systems, with critical implications for water resources and the interactions between surface and groundwater.