A spatiotemporal analysis of water quality characteristics in the first-levetributaries in Nanchong Section of Jialing River

Abstract

In this study, the monitoring data of 23 parameters in 25 monitoring sections of the first-level tributaries of Jialing River in Nanchong City during the 13th Five-Year Plan period (2016–2020) were taken as the research object to analyze water environment quality. Results showed that the water quality is gradually improving in this area, and the main pollutant indexes are chemical oxygen demand, total phosphorus, ammonia nitrogen, permanganate index, 5-day biochemical oxygen demand, and dissolved oxygen. Cluster analysis divided the 12 months into two periods and the 25 monitoring sites into three groups based on similarity of water quality characteristics. The water quality of rainy seasons (July–December) was better than that of dry seasons (January–June). Groups 1, 2, and 3 were mainly located in the urban–rural fringe area, mountain area, and urban industrial park, respectively, representing moderate pollution, low pollution, and high pollution areas. Discriminant analysis (DA) presented good results with great discriminatory ability for both temporal and spatial analyses and provided an important data reduction. DA only used nine parameters for temporal analysis, affording approximately 91.7% correct assignations, and 18 parameters for spatial analy-sis, affording 96% correct assignations. Multivariate statistical analysis showed that the four major pollution sources in the basin are industrial wastewater, agricultural runoff, domestic sewage, and livestock pollution. The research results are relevant to the prevention and control of water pollution in the Jialing River Basin of the Yangtze River Economic Belt. The achievement of Nanchong City and the summary of the experience of winning the battle of pollution prevention and control in China take the lead in implementing the municipal river chief system in Sichuan Province.