Water Quality, Influential Factors, and Management Strategies from 2016 to 2020 in the Yangtze River Economic Belt, China

The Yangtze River economic belt (YREB), China is important to the Chinese economy and for supporting sustainable development. Clarifying the relationship between water quality indices and socioeconomic indicators could help improve aquatic environment management in the YREB and our understanding of the causes and effects of water quality variations in other large river basins. In this study, river water quality, factors affecting water quality, and management strategies, and correlations between water quality indices and socioeconomic indicators in the YREB during the 13th Five-Year Plan period (2016-2020) were assessed. The single-factor evaluation method, constant price for GDP, and correlation analyses were adopted. The results showed that: 1) water quality in the YREB improved during the 13th Five-Year Plan period. The number of aquatic environment sections meeting Grade I-III water quality standards increased by 13.1% and the number below Grade V decreased by 2.9%. 2) The values of 12 indicators in the YREB exceeded relevant standards. The indicators with highest concentreation were the total phosphorus, chemical oxygen demand, ammonia nitrogen, and permanganate index, which were relatively high in downstream regions in Anhui Province, Jiangsu Province, and Shanghai Municipality. 3) Ammonia nitrogen, chemical oxygen demand, and total phosphorus emissions per unit area and water extraction per unit area are relatively high in the three downstream regions mentioned above. 4) Increased domestic sewage discharges have increased total wastewater discharges in the YREB. 5) River water quality in the YREB strongly correlated with population, economic, and water resource indices and less strongly correlated with government investment, agriculture, meteorology, energy, and forestry indices. This confirmed the need to decrease wastewater discharges and non-point-source pollutant emissions. The aquatic environment could be improved by taking reasonable measures to control population growth, adjusting the industrial structure to accelerate industrial transformation and increase the proportion of tertiary industries, and investing in technological innovations to protect the environment.