|摘要: ||河川污染指標(River pollution index, RPI)與水質指標(Water quality index, WQI)可表達河川水體水質良窳，環保署應用RPI於河川水質管理，RPI水質參數包含SS、BOD、DO與NH3-N。本研究目的:(1)檢討RPI與水質項目之相關性、(2)檢討RPI與WQI之相關性、及(3)評估WQI取代RPI於河川水質管理。水質資料以環保署2007-2011年全國流域水質監測資料為統計對象。研究結果顯示RPI無法表示水質濃度差異，RPI值隨BOD、NH3-N濃度增加而增大，其相關性之相關係數R2= 0.82-0.86，與SS相關性相當低(R2= 0.04)無法區別河川水質SS大於100 mg/L之差異，故RPI值不適用於高SS濃度之河川。RPI與WQI4、WQI7相關性之R2值皆為0.91，且WQI4與WQI7之相關性R2為0.99，統計學F值檢定顯示兩者皆可取代RPI。WQI4因參數較少，僅有DO、BOD、NH3-N、及SS等四項參數，使判別水質狀態時，易受水質參數變化而影響。以淡水河流域為對象，WQI4判斷屬優良與良好水體比率為48.6%，高於WQI7之比率41.4%，此乃因WQI4水質參數較WQI7少所致。此外，以RPI與WQI7計算淡水河流域各測站2007年至2011年水質改善率，以大溪橋與三鶯大橋為例，RPI值水質改善率為50-55%，高於WQI7水質改善率為10-20%，此乃因RPI值範圍太小(1-10)，相對地WQI7值範圍較大(0-100)，意味WQI7值較RPI值適用於評估河川水質改善成效，且WQI7以河川水體分類水質標準為判定依據。故建議環保署以WQI7取代RPI應用於河川水質管理，以評估河川水質良窳與改善成效。|
The water quality index (WQI) can be applied to river water quality management. The Taiwan EPA uses river pollution index (RPI) to evaluate the performance of river pollution control. The RPI’s water quality parameter includes SS, BOD, DO and NH3-N. The purposes of this study were: (1) to investigate the correlation between RPI and water quality parameters, (2) to examine the correlation between RPI and WQI, and (3) to evaluate the replacement of RPI with WQI7 in river water quality management. The data of river water quality, which was monitored during 2007-2011, was collected from Taiwan EPA. The results show that RPI value increased with increasing both concentration of BOD and NH3-N, and the correlation coefficient values (R2) between RPI value and BOD, NH3-N ranged from 0.82 to 0.86. By contrast, the R2 value of 0.04 was very low between RPI and SS, implying that RPI was unsuitable for SS concentration higher than 100 mg/L. WQI4 has the same water quality parameters with RPI, while WQI7 has three additional parameters as pH, total phosphorus (TP) and coliform groups. Both R2 values between RPI and WQI4, WQI7 are 0.91, and statistics F-value test shows that both WQI4 and WQI7 could replace RPI. The amount of 48.6% of river water quality could be classified as excellent and good grade by WQI4 and it became lower as 41.4% by WQI7. This is due to water quality parameters of WQI4 less than that of WQI7. In addition, this study calculated the change of RPI and WQI7 values at Tamsui River Basin’s monitoring stations water quality between 2007 and 2011 to evaluate the improvement ratio of river water quality. The results show the improvement ratio by RPI value was 50-55% higher than that of 10-20% by WQI7 value. This is because that the value range of RPI (1-10) is smaller than that of WQI7 (0-100). It implies that WQI7 was more suitable than RPI for evaluating river water quality improvement ratio. Moreover, WQI7 is based on the surface classification and water quality standards. Therefore, it could conclude that EPA can replace RPI with WQI7 to manage river water quality and evaluate improvement ratio of river water quality.