Changes in China’s river water quality since 1980: management implications from sustainable development

Human activities and climate change threaten water quality in China’s rivers. Using a 16-year (2003–2018) monitoring dataset and stacking machine-learning models, the authors simulated monthly concentrations of total nitrogen (TN), ammonia-nitrogen (NH4-N), total phosphorus (TP), and permanganate chemical oxygen demand (CODmn) for 613 sub-watersheds across 10 major river basins for 1980–2050. Results show marked water quality improvements for TP, NH4-N, and CODmn, but not for TN, likely due to the absence of a TN control target and assessment system. Quantitative attribution indicates anthropogenic factors are the primary controls on TN, TP, and NH4-N relative to climatic and geographical drivers, while CODmn varies by basin. Integrating all SDGs relevant to water quality, the study argues that water resources, environment, aquatic ecology, and water security must be managed collectively to improve ecological status.