氣候變遷是人類社會在21世紀的最大挑戰，是追求永續發展不可避免的影響因素。在企圖減少溫室氣體排放，以減緩氣候變遷速度同時，面對仍然變動的氣候，進行合理的調適工作逐漸受到各國的重視。然而，規劃合理可行的調適策略，必須先了解未來氣候變遷趨勢與經濟社會的變動。跨政府氣候變遷研究小組(IPCC)針對未來可能的全球經濟社會變動趨勢，研擬出四種基本情境(A1, A2, B1, B2)，用來預測氣候變遷。本研究則利用IPCC情境，推估台灣在四種情境下的社會經濟變化，並進一步預測滿足四種社會經濟情境下的用水需求。結果發現，比較2006年與情境下2100年的用水量，2100年總用水量將多出30.5%~72.4%，其中A2情境的人口增加最多，其民生用水與農業用水分別增加60.1%與80.3%。本研究從上而下(top-down)的方式進行分析，加上計算過程的參數限制，最終量化數值可能具有高度不確定性，但研究結果顯示不管何種情境，若各用水採取與目前相同的用水效率，本世紀末用水需求量可能多出三分之一在總可用水量不變下，台灣未來缺水情況應提早重視並獲得控制。
Adapt to climate change and seek to a climate resilience society is an important issue for national sustainability development. However, to design a rational adaptation policy needs the comprehensive understandings of the future climate change and future socioeconomic change, which are difficult to be determined. In this study, the Taiwan water demand is projected based on IPCC (Intergovernmental Panel on Climate Change) SRES (Special Report on Emissions Scenarios) in order to inform further adaptation policy-making. The total water demand is divided into three water use, i.e., domestic water use, agricultural water use, and industrial water use. The results show that the water demand quantity in 2100 is more than 30.5% to 72.4%, compared the 2006 level. Especially, the increment of domestic water use and agricultural water use in A2 scenario is high to 60.1% and 80.3%, respectively. The top-down approach might include highly uncertainty due to the limitations in calculations. However, at the present speed of water use, more than one third water than the current level might be exceeded in the end of this century no matter which scenario is applied. The warning message should be taken considerately and to adapt the possible water shortage problem.
