由於經濟與人口成長、都市化、水污染、氣候變遷等問題以及水資源供給面開發日 益困難，水資源的供需失衡問題日益嚴重，因此，如何有效率地利用水資源，實為當代 之一重要課題。本計畫即擬以濁水溪南岸（雲林地區）為例，探討水資源在民生、工業、 以及農業之用水分配以及用水效率。由於水資源在水質許可下是可以重複利用的資源， 因此要使水資源有效利用，便一定要將迴歸水納入考量。此外由於濁水溪沖積扇擁有豐 富的地下水資源，因此一直以來此地區皆以地表水與地下水聯合運用之型態利用水資 源，然而卻非永續之利用方式，因此造成地下水超抽、地層下陷等問題。本計劃將以迴 歸水與聯合運用為探討重點，在理論上建立最適化分析模型，並以雲林地區之實證資料 進行模擬，相信研究成果將具有重要的政策意涵。 Because of economic and population growth, urbanization, water pollution, climate change, and new water supplies have been very difficult to develop, water resource has become increasingly scarce in relation to the demands placed upon it. How to use water efficiently has therefore become a very important contemporary issue. This research proposes to study the water allocation and use efficiency among various water-using sectors by taking advantage of the empirical data from Yun-Lin area (which is located at the southern part of the Chou-Shui River). To achieve the goal of water use efficiency, we must take return flows into consideration as water is recyclable. In addition, because the groundwater storage at the alluvial cone of the Chou-Shui River is abundant, a conjunctive use of surface water and groundwater is the traditional type of water use in this area. However, the water is not used sustainably. The over extraction of groundwater has resulted in severe land subsidence problem. This research will build a theoretical optimization model to analyze water use efficiency, which emphasizes the characteristics of return flow and conjunctive use. Then I will use the data from Yun-Lin to do simulations with this model for different scenarios.