Significant impacts of artificial regulation on nutrient concentrations and transport in Huanghe River

• DOI: 10.1007/s00343-024-3234-6
• Publication Date: 2024-07-23T02:01:41Z
• Authors: Fuxia Yang; Zhigang Yu; Alexander Felix B...; Hongtao Chen; Mengfan Wu; Jing Liu; Dandan Li; Qingzhen Yao; Yao Gong; Xinyu Li; Wenyan Gu
• Keywords: water-sediment regulation scheme; Huanghe (Yellow) River; nutrient flux; 0207 environmental engineering; nutrient form; ecological effect; 02 engineering and technology

Human perturbations such as dam regulation have led to significant changes in nutrient flux, structure, and spatiotemporal distribution through rivers and have greatly influenced coastal and estuarine ecological environments. Based on the data from 2001–2019, the impacts of the water-sediment regulation scheme (WSRS) in the Huanghe (Yellow) River on nutrient concentrations, forms, fluxes, and potential ecological effects on the Huanghe River estuary and Bohai Sea were analyzed. Nutrient concentrations and forms were significantly influenced by the different regulatory modes and were associated with hydrological and biogeochemical processes. The concentrations and forms of nutrients were strongly influenced by the riparian floodplains and scouring process of the downstream riverbed at the water draining stage, while they were influenced mainly by the mixing process in the Xiaolangdi Reservoir at the sediment desilting stage. Compared with those in non-WSRS years, the seasonal distributions of water discharge and nutrient fluxes in WSRS years significantly changed, with peaks occurring at least one month earlier than those in non-WSRS years. Nitrate (NO3-N), phosphate (PO4-P), and silicate (SiO3-Si) fluxes during the WSRS, which were strongly controlled by water discharge at Lijin (the nearest hydrological station to the river mouth), accounted for more than 20% of the annual fluxes; these fluxes were more than 5–9 times greater than those during the same period in non-WSRS years. WSRS exacerbated nutrient imbalances and increased Pyrrophyta/Bacillariophyta ratios by 231% in the Huanghe River estuary, resulting in chlorophyll-a peaks in the Bohai Sea shifting from spring to autumn in the 20th century to spring-summer in the 21st century.