雨量轉換成河川流量的比例決定了直接可利用水資源量，然而卻鮮少研究全面性地針對全臺灣的集水區瞭解其雨量─流量關係，河川流量是區域發展的核心資源，其量化為評估區域水資源永續利用之必要步驟。本研究利用TCCIP公告的全臺灣雨量網格資料及水利署與臺灣電力公司所提供的流量資料，選定107個集水區分析其自1960年至2017年間平均年雨量、年流量、年逕流係數、年實際蒸發散的空間分佈及歷年之變化趨勢，並建立107個集水區年時間尺度之雨量─流量線性關係式（年流量＝a×年雨量＋b），做為河川流量水資源估計的基礎工具。結果顯示，全臺灣各集水區年流量在空間及時間上無顯著變化趨勢，然對應流量資料之年雨量卻普遍呈上升趨勢，儘管未達統計顯著卻導致共有21個集水區的逕流係數達顯著下降的趨勢並主要集中在北區與南區，而逕流係數顯著上升的區域則集中於中區及東區；所有集水區的雨量與流量均呈現非常好的線性關係且達到顯著，R^2值大於0.7的測站數高達71個；集水區間a、b值的差異及實際蒸發散的估計無空間分佈特性，且有25集水區的年流量大於年雨量，其原因待查。但不管其發生的原因為何，發生的原因均持續地且系統性地影響著雨流關係，顯示良好的雨量關係式仍有很高的應用價值。
Runoff or streamflow, rather than rainfall, is a directly abstracted water resource. Rainfall-runoff relationship informs the amount of rainfall being converted to runoff, which has been rarely documented for the island-wide watersheds in Taiwan. Runoff determines the regional development of Taiwan. Therefore, quantification of runoff is crucial for the evaluation of sustainable water resource use. In this study, gridded rainfall data, produced by Taiwan Climate Change Projection and Information Platform Project (TCCIP), and runoff data, provided by Water Resources Agency and Taipower Company, from 1960 to 2017 were used to understand the spatial patterns and trends of annual rainfall, runoff, runoff coefficient and actual evapotranspiration for the 107 watersheds. Rainfall-runoff relationships, i.e. annual runoff = a × annual rainfall + b, for the 107 watersheds were also constructed. The results show that there were no spatial and temporal trends for the annual runoff but there was overall an increasing trend for the annual rainfall, leading to a significantly decreasing trend in runoff coefficient at 21 watersheds, mainly in Northern and Southern Taiwan. Every watershed had a very good rainfall-runoff relationship, and there were 71 watersheds where their relationships possessed R^2 values greater than 0.7. No distinct spatial patterns were found for coefficients a and b and actual evapotranspiration. There were 25 watersheds where annual runoffs were larger than annual rainfall forunknown reasons. Nevertheless, it is speculated that the reasons consistently influence the rainfall-runoff relationships, making them applicable to water resource management.
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