Temporal and Spatial Variation Characteristics of Water Quality in the Lower Reaches of Danshui River in Guangdong

Abstract

【Objective】Taking the lower reaches of Danshui River, a major regulated river in Guangdong Province, as the research object, the temporal and spatial dynamic changes of pollutants in its main tributaries were investigated.【Method】Through the method of remote sensing image interpretation combined with field investigation, monitoring points were arranged for different land use function areas in tributary basins of the lower reaches of the Danshui River in Guangdong Province, and monthly field monitoring of water quality in cross sections was carried out. Single factor evaluation method, comprehensive pollution index method and anomaly coefficient method were used to evaluate and analyze the spatio-temporal variation characteristics of water quality.【Result】In the main tributaries of the lower reaches of the Danshui River, except for Maxi River, the monitoring indexes of the catchment sections of other tributaries were significantly higher than those of the source water quality, and TN was the main pollution factor. During the study period, the NH4+-N compliance rate increased from 69.70% to 79.17%, and the COD compliance rate increased from 68.94% to 70.08%.In terms of annual variation, the fluctuation of the comprehensive pollution index of the Maxi River was the most stable, and the fluctuation of the Dali River was more severe, which was obviously higher in January, April, November and December compared with other months. The contribution rate of NH4+-N in the Dali River accounted for 15%-37%, and the TN was an important water pollutant in the Dali River. The TN pollution index in dry period was significantly higher than that in wet period, however, the TP pollution index was slightly lower than that in wet period. In general, the comprehensive pollution index of each tributary in the dry period was higher than that in the wet period. Spatially, the water quality of the west bank tributaries of the Danshui River was better than that of the east bank. Industrial zone, urban living area and rural residential area had a great impact on the TN, NH4+-N and TP flowing through the river section, respectively.【Conclusion】In the lower reaches of the Danshui River, the water quality of the Maxi River on the west bank is generally better, while that of the Dakeng River, the Shatian River and the Dali River on the east bank is relatively poor. The pollution indexes of various tributaries have no obvious change rules during the year, and the pollution indexes of the river reaches near industrial, urban and rural residential areas are higher than those of other river reaches.

Keywords

• the danshui river
• water quality assessment
• spatiotemporal characteristic
• anomaly coefficient
• comprehensive pollution index