Human regulation reshapes nitrogen and phosphorus transport in the highly managed Yellow River Basin

Study region Yellow River Basin (YRB), China. Study focus This study quantified how large-scale human regulation reshaped total nitrogen (TN) and total phosphorus (TP) transport in one of the world’s most engineered river systems. Using a basin-wide dataset (2016–2022) of discharge, sediment load, TN/TP concentrations, water allocation, and Water–Sediment Regulation Scheme (WSRS) records, we quantified TN and TP fluxes along the mainstem and 11 major tributaries and assessed the impacts of allocation and WSRS on annual loads and seasonal regimes. New hydrogeological insights from the region Export to the Bohai Sea (Lijin) was 103,626–117,122 t yr⁻¹ for TN and 567–2365 t yr⁻¹ for TP. Tributary inputs were dominated by the Wei River, Huangshui River, and Fen River. Water diversion removed 73.9% of TN and 89.7% of TP relative to downstream export, indicating that human water consumption largely controls the basin’s nutrient balance. In contrast, WSRS redistributed nutrient transport temporally by generating short-term pulses and preferentially enhancing TP export through sediment mobilization. These pulsed P inputs may temporarily alleviate P limitation but do not offset the persistent N enrichment in the Bohai Sea, potentially increasing eutrophication risks. Overall, human regulation overrides natural controls on nutrient transport in the YRB, underscoring the need to incorporate regulated flow and sediment regimes into integrated river–sea nutrient management.