Table 5.

Impact of each factor on the identification of CSAs (in %). The value represents the ratio of the same basins identified as CSAs before and after the elimination of each factor and the range of the value refers to the results based on BOD, TP, and TNP

Rank	−Factor 1a	−Factor 2	−Factor 3	−Factor 4	−Factor 5	−Factor 6	−Factor 7	−Factor 8	−Factor 9
Total (top 30%)	89.8–94.9	98.3–100.0	88.1–93.2	89.8–91.5	84.7–88.1	89.8–93.2	88.1	94.9–96.6	74.6–84.7
Level 1	90.0–95.0	95.0–100.0	90.0–95.0	85.0–90.0	90.0–95.0	85.0–90.0	90.0–95.0	90.0–95.0	80.0–85.0
Level 2	68.4–84.2	89.5–100.0	68.4–84.2	57.9–73.7	73.7–78.9	68.4–73.7	57.9–78.9	84.2	26.3–36.8
Level 3	55.0–65.0	95.0	55.0–65.0	50.0–60.0	45.0–60.0	55.0–60.0	35.0–55.0	75.0–90.0	10.0–20.0

^a“−” indicates the elimination of the factor, with (1) NPS pollution load per unit area, (2) residential/industrial NPS pollution load per unit area, (3) mean water quality, (4) excess percentage of water quality standards, (5) water quality index, (6) impervious area, (7) soil slope, (8) topsoil type, and (9) rainfall