曾文溪流域水庫疏濬對河川水質之影響

本研究以曾文溪流域為研究對象，彙整分析行政院環境保護署2011至2017年之河川水質監測數據資料，藉此研究上游水庫疏濬清淤對曾文溪流域水質變化趨勢，水質項目選定懸浮固體，並利用盒鬚圖、WQI7水質指標、以及懸浮固體合格率等分析進行研究。由2011至2017年各水質監測站WQI7指數值結果，多數水質測站之水體水質仍與現行地面水體分類標準相符，惟2013至2017年懸浮固體濃度呈上升趨勢，而懸浮固體合格率則呈下降趨勢，推究可能受上游水庫疏濬之影響，因疏濬清淤作業多利用颱風豪雨將泥砂排入河川，進而影響河川濁度及懸浮固體濃度。統計曾文溪橋WQI7指標值，為中等水體（與現行地面水體分類之丙類水體相似）比例達62.7％，然現行地面水體分類將曾文溪橋劃定為乙類水體，故建議可針對曾文溪橋水體分類進行調整。

關鍵字

河川水質；水質指標；水庫疏濬

並列摘要

This study focuses on Zengwen Basin, and tries to analyze the water quality monitoring data of the Environmental Protection Administration Executive Yuan from 2011 to 2017. The study tries to figure out the trend of water quality changes in the dredging from the upstream reservoir in the Zengwen Basin. The study focuses on suspended solids and uses methods such as box-and-whisker plot analysis, WQI7 water quality index analysis, and qualification rate analysis. Analyzing the WQI7 index values of water quality monitoring stations from 2011 to 2017, the most water quality stations still maintain the same surface water classification standards. But from 2013 to 2017, the concentration of suspended solid has rose, and qualification rate of suspended solid has dropped, this suggests that the effect of the dredging from the upstream reservoir in the Zengwen Basin. Because dredging operations use typhoon and heavy rain to discharge muddy sand into rivers, which in turn affects river turbidity and suspended solids concentration. Statistics the WQI7 of Zengwenxi Bridge, and the proportion of Category C water bodies is 62.7%. The current classification of surface waters has designated Zengwenxi Bridge as Category B water bodies, so it is recommended to adjust the water body classification of Zengwenxi Bridge.