The researchers studied water quality in China's largest river, the Yangtze River, and found that it is influenced by factors like land use, hydrology, and climate. They used different methods to analyze the water quality and found that the wet season had higher levels of pollutants compared to the dry season. The upper reach sites near the Three Gorges Dam had better water quality. The main drivers of water quality were land use, water flow, and climate. Decision-makers should consider both human activities and natural factors to protect water quality in large rivers.