淡水資源耗用與使用的生命週期衝擊評估方法建立

Abstract

近年來全球人口成長及經濟發展快速，超量抽取地面水與地下水、污染淡水資源，以及使用效率不彰，造成淡水資源壓力提升與生態多樣性損失，產生的衝擊橫跨人體健康、生態系品質及資源存量三大面向。生命週期評估利用科學連結推導水資源消耗造成的潛在衝擊與損害，近年成為評估水資源耗用與使用衝擊的新興方法。 然而，現有方法大多考量水量變化，不討論水質對可用水量的影響，除此之外，淡水資源耗用與使用的衝擊具有區域與時間差異，早期生命週期評估模式為通用性模式，計算的時間尺度以年為主，空間尺度依研究者偏好而異，使得評估結果不能精準反映時空變化下的特徵。 本研究的目的為考量水質、水資源的時間與空間可及量，以及用水標的之間的競爭，設計水資源耗用及水資源使用兩個衝擊類別與對應的特徵因子(水壓力)計算方法，期望評估地面淡水耗用對集水區造成的潛在衝擊；另外，本研究模擬節水情境產生不同情況下的特徵因子，並以臺灣3個科學工業園區的所有基地作為研究對象，評估所有情境下基地地面水淡水資源耗用與淡水資源使用的潛在衝擊。 研究結果顯示，不論是耗用水壓力或是水質水壓力，枯水期壓力均大於豐水期壓力；耗用水壓力於各情境中均可反映標的用水競爭排擠的現象，尤其全標的節水可使水壓力下降更快，整體來說標的優先序愈低，壓力愈大；水質水壓力反映用水量與標的可用水質水量的比值，農業水質水壓力特別大，節水情境下水壓力變化很小。案例分析結果顯示，南科臺南園區水耗用衝擊最大，南科高雄園區則是水使用衝擊最大，主要原因為水壓力屬於重度剝奪；節水情境下以全標的節水使園區造成的水資源耗用衝擊降低5%~17%，而水資源使用衝擊降低1%~6%。 本研究所建立之生命週期評估衝擊方法，提供新的水壓力指標與看待水資源衝擊的新視角，並補足目前水資源地域性潛在衝擊評估的方法斷層，未來可應用於國內外各項產品服務的評估，或是做為水資源管理指標。

A substantial amount of evidence has indicated that freshwater use and consumption cause water scarcity, damage to human health, and ecological disorder. Life cycle assessment (LCA) is a promising approach that can be used to estimate the impacts caused by water consumption and water use. However, assessment schemes that address the potential environmental impacts of freshwater consumption and use have seldom been provided in LCA methods. The spatial and temporal scales of LCA models are not suitable for Taiwan, as most LCA models are site generic and annual. A majority of studies have also neglected reservoirs as an available water source and the impact of water availability on water quality. Therefore, our study proposes an LCA approach in which the regional water availability, wastewater quality, competition of water among all sectors, and spatial-temporal factors are considered. This LCA approach consists of two impact categories: water consumption and water use, in addition to the corresponding watershed-based and sector-wise characterization factors (also called water stress) during high/low-flow periods. The developed approach was applied in a case study of industrial parks in Taiwan. In addition, four scenarios of water conservation were generated to estimate characterization factors and potential impacts. The results of the water stresses in Taiwan exhibited higher water stresses during low-flow periods than during high flow periods. And the higher priority of sector was, the lower water stress of sector would be. Moreover, water stresses for water consumption of watersheds in western Taiwan were higher than that in eastern Taiwan; and water stresses of agriculture for water use of each watershed was at the state of heavily deprived. In scenarios of water conservation, water stresses of water consumption visibly decreased for the competition of water among all sectors, but there were slight changes on water stresses of water use. With regard to impacts of the case study, science industrial parks with the greatest amount of impacts contributed to consume freshwater from the watersheds at the high water stress and discharge wastewater with worse water quality to the watersheds at the high water stress. Therefore, Southern Taiwan Science Park at Tainan had the highest potential impact of water consumption and Southern Taiwan Science Park at Kaohsiung had the highest potential impact of water use. At the scenario of water conservation of all sectors, impacts of water consumption declined 5%~17% and impacts of water use dropped 1%~6%. Our proposed approach provides a new method to understand the impacts of freshwater consumption and freshwater use.