This study was to investigate characteristics of Seoho watershed in Suwon city. BOD5 and SS were selected due to the one of the important factors of the water qualities. Monitoring was conducted monthly for four years during the non-rainfall time. Also, we have been monitored BOD5, CODMn, SS, TN and TP with two times sampling after the rainfalls. The highest concentrations of BOD5 and SS were observed in downstream compare with upstream and midstream during the non-rainfall time. No change was

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... bserved in BOD5 and CODMn during the non-rainfall time and after the rainfalls. The monitoring result indicated that the concentration of SS was the highest in downstream after the rainfalls. We have collected the samples two times after the rainfalls. The rainfall intensity in first sampling was two times higher than second sampling. TN and TP concentrations were increased with increasing the rainfall intensity at all stream. The ESB (Ecological Score of Benthic macroinverterbrate community) index was used to evaluate the statement of stream. ESB results were identified that the upstream is protected waters and the down and midstream is reformed waters. EBS analysis results indicated that the Seoho watershed was β-mesosaprobic at all stream.