Water Quality Evaluation and Variation Trend Analysis of Rivers Upstream of the Dahuofang Reservoir in China

Abstract

The Dahuofang Reservoir is one of the most important water sources in Liaoning Province, China, so it is critical to identify the status and evolution characteristics of its water quality. Six monitoring indicators were selected to analyze water quality differences and variation trends of each indicator in three inlet sections of the reservoir during different hydrological periods from 2003 to 2021, and an improved comprehensive pollution index method was proposed to study the pollution variation trends. The results showed three findings. (1) The water quality of the three rivers is better in high water periods than that in low water periods. (2) In terms of the spatial state of the water environment, water quality of the Hun River is the worst, the Suzi River is poor, and the She River is better. The worst indicator of the three rivers, TN (total nitrogen), has exceeded the standard for many years (Grade IV–Inferior Grade V). TP (total phosphorus) in the Hun River, which has deteriorated severely since 2013 and is positively correlated with rainfall; it is mainly influenced by pollution from agricultural activities. (3) The P value obtained by the improved method is lower than that of original method, which is mainly because TN is relatively stable, and the exceeding standard of TP is not as serious as TN. The improved method takes into account the interactions and fluctuations of indicators, so that it can reflect the pollution situation more scientifically. These results are helpful to evaluate the pollution status of surface water. It is suggested that water be transferred appropriately to improve water quality and take necessary management measures to reduce TN and TP in the Hun River.

Keywords

• comprehensive pollution index
• water quality evaluation
• trend analysis
• coefficient of variation
• Dahuofang Reservoir
• Hun River