EFFECTS OF RAINFALL CHARACTERISTICS ON RIVER WATER QUALITY IN DIFFERENT WATER PERIODS: A CASE STUDY OF NANCHANG SECTION IN THE GANJIANG RIVER

In this paper, we analyzed the rainfall characteristics of different water periods in Nanchang section of the Ganjiang River by Mann-Kendall test and correlation analysis, and investigated the influence of rainfall characteristics on the water quality of this section, taking the Zhoufang national examination section in Nanchang section as the object. The results showed that: 1) COD and ammonia nitrogen concentrations at this section of Nanchang section basically met the surface water category Ⅲ standard in all hourly periods throughout the year, but TP concentrations mainly exceeded the surface water category Ⅲ standard during the high water period, followed by the dry water period, and TN concentrations exceeded the surface water category Ⅲ standard except in 2019-08 to 2020-02; 2) the intra-day time-averaged coefficients of variation of TN and TP at the cross sections were small (<15%), while the intra-day time-averaged coefficients of variation of COD, ammonia nitrogen and turbidity were greater than 15%; 3) the concentration of ammonia nitrogen tended to peak in the first month of the year when rainfall was higher, and TP and flow were significantly correlated (R²=0.728, P<0.01); 4) in the high water period and flood period, the section water quality exceeding the standard mostly occurred after strong rainfall; when the dry period occurred after strong rainfall, water quality parameters with rainfall had a significant increase.