The Spatiotemporal Variations and Potential Causes of Water Quality of Headwaters of Dongjiang River, Southeastern China

Abstract

Due to the steep slope and short concentration time of flow in mountainous areas, the water environment of headwaters is easily disturbed by human activities. The spatial-temporal variation of the water environment is a key issue for the implementation of river restoration. This study aims to explore the spatial-temporal characteristics of water quality and its pollution sources of the headwaters of the Dongjiang River. Water quality monitoring data over the past 6 years were collected and analyzed using principal component analysis, equal standard pollution load, and multivariate statistical analysis. The results show that the water quality presents significant spatial heterogeneity, where the water quality in the middle and lower reaches is poor. The concentrations of ammonia nitrogen and total phosphorus in the middle and lower reaches were 18.3 and 9.5 times higher than those in the upper reaches, respectively. The water quality has tended to improve recently because of ecological compensation and environmental management. Correlation analysis shows that there were significant positive relationships among major pollutants. Critical source areas were identified, which implies that the most polluted area is located in the middle reaches. Studies have also shown that the water pollution mainly comes from livestock and poultry breeding, industrial sewage discharge, and cultivated land. Controlling the scale of construction land and adjusting the industrial structure is one of the main measures for eradicating water environment problems in headwaters in mountainous areas.