基于水足迹核算的北京市水资源保障研究

A Study on Water Resources Guarantee in Beijing City Based on Water Footprint Evaluation

本文利用水足迹对北京市水资源占用进行估计,得出2006年北京市水资源实际占用量为138.28×108m3,能更真实反映北京市水资源实际占用情况。从产业结构及消费构成分别分析了水足迹的情况,得出农作物和动物产品虚拟水消耗是水足迹消费的主要组成部分,粮食及肉类是耗用水资源的主要消费产品。北京市水资源压力为1.37,工业用水、生活用水、农产品引进、生态环境保障、动物类及农作物产品用水相应水资源压力分别为:0.082、0.135、0.570、0.016、0.350和0.213。市外引入水资源高达59.78×108m3,对外依存度为0.43,说明北京市本地水资源难以满足社会、经济发展需求。分析北京市水足迹组成及水资源保障情况得出结论,市内用水结构优化、虚拟水引进及南水北调是水资源安全保障的基本措施。

A concept of water footprint was developed and elaborated in the present work in order to offer an indicator depicting water use with regard to consumption of people. The water footprint of a city is defined as the volume of water needed for the production of goods and services consumed by inhabitants in the city. The water footprint primarily contains industrial water, domestic water, agricultural water as well as environmental water. The domestic water, environmental water and the part of industrial entity water consumption are estimated by the entity water, which can be obtained from statistical data. The agricultural water and other virtual water consumption can be calculated by means of the footprint proposed by A.Y. Hoekstra and A. K. Chapagain in year 2002. Total volumes of water use in the agricultural sector are calculated on the basis of the total volume of crop productions and corresponding virtual water content, which can be calculated by the virtual water content of primary crops （m3/ton） by the total volume of yield. The methodology developed by the Food and Agriculture Organization of the United Nations （FAO） is adopted to calculate crop water requirements. To calculate the virtual water content of live animals （m3/ton）, the results about Chinese live animals from A.Y. Hoekstra were utilized in this study. The developed concepts and methods were applied to calculate water footprint in Beijing. Results showed that the true water occupancy quantity was roughly 13.828×109 m3, which seems to be a more reliable quantity compared with the statistical data. Through analyzing the industrial structure and consumption pattern, it was found that grain and meat were two major products consuming water resources; meanwhile, planting and animal industries were major industries consuming water resources. Also, the water resources pressure index and different partial pressures were calculated, showing a value of 1.37 of the water resources pressure index and the partial pressures caused by industrial water, domestic water, agricultural product introduction water, eco-environment safeguard water, animal products and crop water of 0.082, 0.135, 0.570, 0.016, 0.350 and 0.213, respectively. The water resources imported by virtual water trades were estimated to be 5.978×109m3, and the external dependence degree was about around 0.43, which may be indicative of that native water resources cannot satisfy water demands and support sustainable development of economy and society. Furthermore, the authors analyzed the water footprint structure and water guarantee situations in Beijing. It was suggested that optimizing the water use structure, importing virtual water and the Water Transfer Project from the South to the North of China will be basic measures to ensure water supply in Beijing. The water footprint concept introduced in the study can be an effective and appropriate way to analyze water guarantee situations in future studies.