水里溪上游集水區地景型態與溪流水質關係之研究

Abstract

本研究目的為探討地景型態與溪流水質關係，希望能提供資訊來協助集水區尺度的土地管理。本研究於水里溪上游五個集水區對14個水質變數進行歷時14個月之溪流水質監測。首先利用不同的統計方法呈現水質變數於空間上的變化及對水質資料進行縮減及資訊萃取，此外，以五個集水區之土地利用比例及地景生態指標分別與溪流水質變數進行相關分析，並探討濱水帶與整個集水區之土地利用情形何者對溪流水質影響較大。結果顯示，WC-4及WC-5取樣點有較高的SO42-濃度，可能為地質條件差異造成；因素分析萃取出五個因素，此結果顯示沒有單一且特別明顯的因素可以解釋14個水質變數的變異情形；集群分析可將集水區分為三群，月份則可區分為二群；溪水中NO3-濃度與檳榔園比例於濱水帶25公尺內呈顯著正相關；地景破碎會使溪流量增加，且檳榔園比例較多使溪流量變動較大，而森林具有調節流量功能；森林及草地區塊面積較大及完整，溪流水中Cl-及NO3-濃度較低。因此，未來國內集水區水質研究可運用多變量分析途徑來協助集水區水質的特徵化及水質監測計畫設計的最佳化，此外，地景生態指標為一項有利的工具，可用來監測溪流水化學改變。The purpose of this thesis was to investigate the relationships that existed between landscape patterns and stream water quality, in the hopes of providing information to help land management at a watershed-level. Fourteen water quality parameters have been monitored on five sampling sites within fourteen months in upstream watershed of the Shui-Li creek. First, different statistical techniques were applied to interpret the spatial variation of, and to reduce the information of stream water quality. In addition, correlation analysis was performed to identify the relationships between land use compositions, landscape metrics and stream water quality variables. Moreover, this study addressed the issue of whether land use near streams influence steam water quality more than land use over the entire watershed. The result of data analysis indicates that there are higher SO42- concentrations at the sampling sites of WC-4 and WC-5, which maybe result from the difference of geological conditions. Factor analysis shows that stream water quality data consists of five components, but there is no one that can explain the great amount of variation in the fourteen parameters. Cluster analysis suggests that monitoring sites and frequencies can be consolidated. NO3- concentrations was positively correlated with the land use of betel palm plantation within 25m buffer. The stream discharge will rise as a landscape tends to fragment. The variation of stream discharge would increase at a watershed where the proportion of betel palm plantation is large. However, forested land has the agent of regulating stream discharge. As patch area of forested land and grassland are larger and more compact, Cl- and NO3- concentrations become lower, respectively. In short, the findings of this study can be drawn: one is that study of stream water quality can use multivariate analysis to identify the characteristics of water quality and optimize the design of monitoring programs within Taiwan watersheds in the future. The other, landscape metrics are useful to monitor the change of in-stream water chemistry.