基于投入产出分析的北京市虚拟水核算

Virtual water analysis for Beijing based on input-output model

城市化进程的加快与工农业的迅速发展使城市水消耗量日趋增加。水资源短缺不仅会造成居民生活质量下降,还会制约社会经济的可持续发展。从贸易和消费的角度核算虚拟水可为研究城市水资源管理提供新的视角。通过投入产出分析了构建了城市系统虚拟水核算模型,利用虚拟水直接和完全用水系数、虚拟水消费量等指标分析城市虚拟水消耗和虚拟水进出口特征。以北京市为例,利用2012年北京市投入产出表和部门的水资源消耗数据核算不同部门的用水系数、最终消费虚拟水量、虚拟水进出口贸易量及部门间虚拟水流转量。结果表明:北京市为虚拟水净进口城市,净进口虚拟水量6.77×10~9m^3,相当于北京市虚拟水用水总量(8.25×10~9m^3)的82%,农业和制造业为主要虚拟水进口部门;北京市虚拟水出口结构存在不合理之处,经济投入产出表中各部门出口总额占最终消费的79.9%,但出口产品消耗的虚拟水占了最终消费隐含虚拟水的85.04%,其中农产品消耗6.7%虚拟水但经济收益仅占1%,说明北京市出口以较大的虚拟水消耗量换取了较少的经济收益,需要减少虚拟水含量较大但经济价值不高的产品出口(如农产品);识别出的主要虚拟水流出-流入关系部门包括农业-制造业,农业-服务业和制造业-建筑业等部门的关联关系,可成为减少间接水消耗的关键路径。

Urban water consumption has increased along with growing urbanization and the rapid development of industry and agriculture. Water resources shortage has been a strict constraint for sustainable urban development. Accounting for the water embodied in trade or final demand can provide a new perspective for urban water consumption. In this paper,we proposed an urban virtual water accounting framework to calculate the water use coefficient,virtual water consumption and virtual water trade volume based on input-output（ IO） analysis. We used the IO table of Beijing in 2012 and sectoral water consumption to study the sectoral virtual water consumption and virtual water flows among sectors. The results show that Beijing is a net importer of virtual water,importing 6.77×10^9 m^3,equal to 82% of the total virtual water in 2012（8.25×10^9 m^3）. Agriculture（Ag） and manufacturing（Ma） are the main import sectors. The export structure of Beijing needs to be adjusted due to its huge virtual water exports,which accounted for 79.9% of the final demand,whilst 85.04% virtual water consumption was used for final demand,and,agricultural products create only 1% economic benefits with 6. 7% virtual water consumption. These results indicate that Beijing benefits little from the large amount of virtual water exports,and the exports of virtual water-intensified products should be reduced. The main outflow-inflow pairs,including Ag-Ma,Ag-Se and Ma-Co,could be critical pathways for the reduction of indirect urban water consumption.