Evaluation of Spatio-Temporal Variation of Water Quality in Qingyi River Basin Based on Multivariate Statistical Method (K–W Test and Pearson Correlation Analysis) and Improved WQI

Abstract

The Qingyi River Basin is one of the most important water resources in Ya'an City, Sichuan Province, which is related to the social and economic development of Ya'an City and the life of residents. In this study, multivariate statistical method (K–W test and Pearson correlation analysis) and graphical analysis were used to evaluate the temporal and spatial characteristics of water quality in Qingyi River. Based on the evaluation results, seven parameters including I_mn, COD_cr, BOD₅, DO, TP, NH₃-N, As, and F⁻ were determined to construct the improved WQI model. The results showed that there were significant spatial differences in I_mn, TP, Cu, As, and EC. In general, the water quality of S1 section is the best, and the water quality of S6 section is the worst. The main pollutants in the basin were TP and NH₃-N, which met the Class II water quality standards, and the other parameters were Class I water quality standards. The change of annual WQI value showed a trend of increasing, decreasing, and then increasing, which met the Class I water quality standard. This study has improved the parameter selection in WQI calculation, which can fully explain the overall change of water quality and potential pollution, and is conducive to the efficient evaluation of water quality with relatively low analysis cost. The research results can provide references and suggestions for the local government and are of great significance for the sustainable development of the water quality of the Qingyi River.