Emergy analysis of regional water ecological–economic system

The theoretical framework and methodology of a water ecological–economic system (WEES) assessment based on emergy synthesis are proposed in this paper. Through calculating ecological and economic inputs and outputs within and outside the complex system, this paper discusses the system's economic situation, water resources development and system sustainability based on a series of emergy indicators. Besides traditional indices, following the principle of system assessment, four new indices, water emergy ratio (WER), water emergy utilization ratio (WEUR), water emergy self-support ratio (WESR), and water emergy density (WED) are formulated to assess the state of water resources development quantitatively. Taking the Zhengzhou water ecological–economic system as a study area, through the comparison of the systematic indicators of Zhengzhou with those of the selected Chinese cities, the general status of the Zhengzhou water ecological–economic system in China is identified. The results also show that most indicators of Beijing are located at middle levels among the selected Chinese cities. In particular, the sustainability, expressed by the indicators emergy-based sustainability index (ESI) and water resources population carrying capacity (WPC) were 1.34 and 1.94 million, respectively, in Zhengzhou in 2005, which indicates that the Zhengzhou WEES is in heavy pressure of water resources and is located at low levels of sustainability.