Insights into spatiotemporal variations of the water quality in Taihu Lake Basin, China

Taihu Lake Basin is highly developed but suffers from perennial water shortages due to pollution. Most studies have been limited to examining the water quality in specific areas, but few have investigated the entire basin. This study was based on official water quality data obtained from 565 sites in the monitoring network, thereby covering the entire basin. The water quality spatiotemporal variations were explored by statistical analysis, and the precise spatial distribution of the main pollutants was analyzed by heat maps. Only 29.09% of the water quality assessment results showed “drinkable,” whereas 28.63% showed “moderate” and “severe” pollution. The “severe” proportion had a significant declining trend (R2 = 0.933) and was affected by the variations of nitrogen that was related to rainfall and anthropogenic activities. The water quality spatial variation was most likely related to anthropogenic influence and land use. The water quality in the developed and densely populated urban areas was poor, especially in downtown Shanghai. NH3-N, TN, TP, BOD5, COD, CODMn, and DO were the main pollutants that affected the water quality. NH3-N and TN were major reduction targets. NH3-N was the main pollutant that deteriorated the water quality in most densely populated urban areas. Many lakes and reservoirs were highly polluted with TN. Controlling domestic sewage may be effective to improve the water quality. This study makes up for the limited research on the water quality spatiotemporal variations in the entire Taihu Lake Basin and provides beneficial information and suggestions for decision-making regarding the water management.