Research on Emergy Evaluation Method of Ecological Water Use Efficiency Based on Comprehensive Benefits

Abstract

Abstract Scientifically evaluating ecological water use efficiency (EWUE) is an effective means to regulate the level of ecological water use in a country or a region. It is also a basic work to achieve high-efficiency use of ecological water under the current situation of water shortage. However, there were few researches on EWUE, and existing studies only focus on eco-environmental benefits generated by ecological water, without considering its impact on economy and society. An emergy evaluation method for EWUE based on comprehensive benefits was proposed in this paper innovatively. Considering the impact of ecological water use on society, economy and eco-environment, the concept of EWUE could be defined. Then, comprehensive benefits of ecological water use (CBEW) were quantified by emergy method, and EWUE was evaluated by the comprehensive benefits of unit ecological water use. Taking Zhengzhou City as an example for calculation. From 2011 to 2020, CBEW increased from 5.20×1019sej to 6.72×1020sej, showing an overall upward trend, and EWUE rose from 2.71×1011sej/m3 (1.27￥/m3) to 1.32×1012sej/m3 (8.10￥/m3）with fluctuation. It showed that Zhengzhou City has paid enough attention to the allocation of ecological water, EWUE at a high level. The method proposed in this paper provides a new idea to evaluate EWUE scientifically, and the results can provide guidance to allocate ecological water resources to achieve sustainable development.