Trend Analysis and Assessment of Surface Water Quality in the Yangzhou Reach of Jinghang Canal

Eight organic and chemical variables were analyzed in surface water samples collected every season over a period of twenty two years. They were determined from seven sampling stations located along the Yangzhou reach of JingHang Canal. The assessment was performed using membership function of twice-slope classification. The results illustrated that: in the past twenty-two years, the water quality of Yangzhou reach of JiangHang Canal stayed mainly between Class III and Class IV. Among the main pollutants, the concentrations of both COD Mn and BOD 5 were decreasing. They were below Class III after 2000. The concentrations of volatile hydroxybenzene and petroleum were remarkably high during 1998 to 2000. In the whole period, they fluctuated in a large degree; the trend of ammonia nitrogen(NH 3 -N) was relatively smooth, oscillating between Class III and Class IV; other variables were in low concentration and did not fluctuate significantly.