氣候變遷造成極端之下，各國對於水資源短缺的議題越來越重視。在台灣，南北雨量分配不均，因此，瞭解水貿易對於水資源的永續管理至關重要。虛擬水透過商品貿易從生產場所送到消費場所。過去有關虛擬水貿易的文獻皆探討國與國之間的驅動因子，鮮少探討城市之間的驅動因子。本論文使用三種計量模型檢測台灣 2013-2017 年 19 個縣市間不同社經因子與天然稟賦效果是否影響水貿易並以毛豬業為例。另外，本研究利用零膨脹卜瓦松模型 (Zero-Inflated Poisson model, ZIP) 與固定效果卜瓦松模型(Fixed Effect Poisson Model)解決縣市間存在零貿易問題。固定效果卜瓦松模型的實證結果顯示，位於消費市場之毛豬拍賣價格每百公斤增加 1%，水貿易增加 1.83%。生產縣的畜牧用地每增加 1%，水貿易增加 1.46%。當溫度上升 1%，水貿易減少 0.22%。當生產和消費縣市之間的降雨量存在差異越大時，會增加城市之間的虛擬水貿易量。本研究進一步將 19 縣市劃分為六大都市與非六大都市，研究結果發現當生產縣市每增加 1%的畜牧用地，六都和 13 縣市分別增加 1.26%與 1.57%的水貿易。當消費縣市聚焦於六都時，實證結果顯示當生產縣市每百公斤的豬肉拍賣價格上漲 1％時，六都減少 1.76％的水貿易。亦即當豬隻拍賣價格在生產縣市上漲時，13 縣市不再供應水至六都。當消費縣市聚焦於 13 縣市的實證結果顯示:當 13 縣市每增加 1%肉類支出時，13 縣市增加 0.34%的水貿易。基於研究結果，本文發現天然稟賦為影響虛擬水貿易的驅動因素。其中，土 地是影響虛擬水貿易的主要因子。當生產縣市的畜牧用地減少時，水貿易也隨之減少。本研究結果重要之政策意涵為生產縣市的水資源永續管理應考慮消費城市的消費行為。因此，各地方政府在制定水資源永續管理的政策時，應考量與各地方政府合作，以達到更好的水資源分配與管理。

In the face of climate change, water scarcity is the major problem facing the globe. In Taiwan, unbalanced seasonal distribution of rainfall causes serious water shortages problems in many cities. Consequently, understanding the trade of water between cities “inter-city” is crucial for sustainable management of water resources. Through commodity trade, virtual water is embodied in commodities, as a result, it flows from the producing area to consumption area. Due to the lack of data, most of the studies on virtual water trade have been conducted at international level, neglecting the local natural water resources and the characteristics of specific society at country level. Using the hog industry in Taiwan as a case study, the study employed three models to examine the social-economic factors and natural endowment that drives the flow of virtual water in intercity trade. In order to take the zero trade into account, the Zero-Inflated Poisson model (ZIP) and Fixed Effect Poisson Model were applied. The results from the Fixed Effect Poisson Model indicate that an increase in hog price by 1% in consuming city, increase virtual water trade by 1.83%. Whilst an increase in land by 1% in producing city, increase virtual water trade by 1.46%. On the contrary, an increase in temperature by 1% in a producing city decreases virtual water trade by 0.22%. Furthermore, the difference in rainfall between producing and consuming cities is more likely to increase intercity trade. In addition, this study divides 19 cities into "six major cities" and "non-six major cities", then analyzes the drivers of virtual water trade between these two groups. As a result, the study found out that if an increase in land in origin city by 1%, the water trade both in six major cities and non-six major cities increases by 1.26% and 1.57%, respectively. When six major cities are regarded as a destination city, the results show that if hog price increase by 1% in origin city, the water trade tends to decrease by 1.76%. When non-six major cities are regarded as a destination city, the results show that if meat expenditure increase by 1% in non-six major cities, water trade tends to increase by 0.34%. This indicates that water trade increased as the meat expenditure increases in non-urban cities. In other words, as prices increase in the meat market in the non-six major cities, the water ceases to supply to the six major cities. These results indicate that natural endowment is the key driver of virtual water trade. The virtual water trade decreased as the land used for livestock shrinks in producing countries. The important implication of the results of this study is that sustainable water resource development in producing counties should take into consideration consumers’ behavior in consumption cities. Consequently, the direction of sustainable water management policy that requires collaboration between local governments for ensuring better management and allocation of water resources.

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