高屏地區的水資源與水污染問題，長久以來備受關注。本研究以水質指數與水污染指數對高屏溪流域地區環境中的水質與水污染變化趨勢進行探討。研究成果顯示高屏溪的水質受到汙染源的控制，與研究區內的人口、染整工業、養豬事業等有空間上分布的關連，亦即污染的時間與空間變化影響水質。 在水污染方面，高屏溪流域水污染指數的趨勢，上游與中游近年來水質轉好。而下游高屏溪主流的部分，其污染指數都保持在中度污染以上，甚至繼續攀高，顯示下游平原地區污染源的嚴重性。此外，在豐水期與枯水期河川水污染狀況比較，在旗尾橋等五個支流測站，呈現豐水期河川污染程度較高的異常狀況，主要由於豐水期的高河川流量使懸浮固體濃度增加，所以RPI值隨之上升。 在水質方面，以水質指數（WQI）為標準，也呈現上下游明顯的差異化。中上游集水區WQI保持在50以上，且水質維持持平或變好。下游的小支流牛稠溪與武洛溪受到養豬廢水的影響，WQI值在40以下，屬於水質劣等的狀況。而主流的高屏大橋與雙園大橋測站由於水量較大，WQI平均值保持在50-60之間，顯示水質屬於中等的情形。在豐水期與枯水期WQI指標比較方面，只有大津橋與南華大橋WQI指標呈現在豐水期較高的異常狀況。

Water resources are a vital element and main issue for the development of southwest Taiwan. This paper concludes that the distribution of pig farms, human population and industries has a significant impact on water quality. The data shows that a reduction of pig population can reduce stream pollution and improve water quality. In this research, the RPI data shows that water quality in up stream area is getting better while the down stream section, including the tributaries, is getting worse. Besides, there is also some difference between the high and low water level period. Generally speaking, the RPI is lower during the high water level period because of dilution. But there are 5 stations that do not show this trend because of the increase in suspended solids during the high water level period. In water quality, the study shows obvious difference between up and down stream sections. WQI in up stream areas is over 50 and it is getting better while it is lower than 40 and getting worse in the nearby tributaries of the down stream section. It is mainly affected by the output of pig farming. The WQI is about 50 to 60 at the Kao-Ping Bridge and Shuan-Yuan Bridge stations because of higher discharge. Moreover, there is some difference between high and low water level periods. Generally speaking, the WQI is higher during high water level periods because of dilution. Only two stations do not show this trend due to the increase of suspended solids in higher discharge.