Parameters Middle reaches Environmental guidelines a M1 M2 M3 M4 Mean Std. Mean Std. Mean Std. Mean Std. Ⅰ Ⅱ Ⅲ Ⅳ Ⅴ DO 8.62 1.14 6.55 1.39 4.5 1.49 5 1.7 ≥7.5 6 5 3 2 CODmn 1.51 0.72 3.27 1.58 6.94 5.15 5.37 2.09 ≤2 4 6 10 15 NH3-N 0.26 0.19 0.75 0.48 0.98 1.03 2.17 1.93 ≤0.15 0.5 1 1.5 2 TP 0.17 0.19 0.25 0.18 0.27 0.14 0.28 0.19 ≤0.02 0.1 0.2 0.3 0.4 Parameters Lower reaches Tributary Environmental guidelines a M5 M6 M7 M8 Mean Std. Mean Std. Mean Std. Mean Std. Ⅰ Ⅱ Ⅲ Ⅳ Ⅴ DO 8.17 1.12 8.38 1.02 8.48 1.06 8.79 1.12 ≥7.5 6 5 3 2 CODmn 3.06 1.13 3.79 1.98 3.55 1.58 2.41 0.92 ≤2 4 6 10 15 NH3-N 0.41 0.2 0.11 0.09 0.16 0.12 0.3 0.16 ≤0.15 0.5 1 1.5 2 TP 0.12 0.04 0.14 0.06 0.15 0.06 0.07 0.04 ≤0.02 0.1 0.2 0.3 0.4

Table 2: Statistics descriptive of selected water quality parameters in the middle and lower reaches of the Min Jiang during 2003-2012.