Research on emergy evaluation method of ecological water use efficiency based on comprehensive benefits.

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 × 1019 sej to 6.72 × 1020 sej, showing an overall upward trend, and EWUE rose from 2.71 × 1011 sej/m3 (1.27ï¿¥/m3) to 1.32 × 1012 sej/m3 (8.10ï¿¥/m3) with fluctuation. It showed that Zhengzhou City has paid enough attention to the allocation of ecological water and 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.

Assessment of eco-economic effects of urban water system connectivity project.

As one of the large ecological infrastructures, the urban water system connectivity (UWSC) project is an important part of urban ecosystem construction. It is helpful for the scientific planning and construction of the project to systematically evaluate the effects. However, due to the complex and various effects of UWSC project, there is no complete effect system and quantitative method. Against this backdrop, the composition and mechanism of positive and negative effects of ecological economics of UWSC project were deeply analyzed to improve the composition system of eco-economic effects in this study. At the same time, the emergy theory was used to put forward the quantification method of eco-economic effect system. Taking the UWSC project in Xuchang as an example, its ecological, social, and economic effects were evaluated. The result showed that the average eco-economic effect of the project is 49.97 million dollars/year. Economic effect and ecological effect are significant, accounting for 82.49% and 15.89% of total effect, respectively. This study can provide reference for comprehensive and unified assessment of eco-economic effects of UWSC project.

Quantitative analysis of eco-economic benefits of reclaimed water for controlling urban dust.

With the acceleration of urbanization and industrialization, urban air pollution, especially dust pollution, has become a global problem. The traditional method to control dust problem is to spray roads with tap water. However, this method will inevitably lead to a huge waste of water resources. Using reclaimed water instead of tap water for dust control can not only achieve the same effect of reducing dust and haze, but also save water resources. In addition, the saved tap water can be used for production and life, thereby obtaining additional benefits. In order to quantify the eco-economic benefits of sprinkling water for dust control, a quantitative method was proposed based on the emergy theory of ecological economics. It was used to calculate the cost of different water resources, the cooling and humidifying benefit, the dust control and haze reduction benefit, and the other use benefit. Taking the 2017 data of Zhengzhou as an example, the results indicated that the cost of using reclaimed water to control dust was reduced by 54%. The total benefit of using reclaimed water was about 1.30-1.80 times that of using tap water, and the net benefit was 4.65-7.17 times. Therefore, the use of reclaimed water instead of tap water for road dust control has advantages of low cost and high eco-economic benefits. The method proposed in this paper can provide quantitative basis for the popularization of using reclaimed water to dust control in cities with serious air pollution and water resource shortage.

Quantitative assessment of ecological compensation for groundwater overexploitation based on emergy theory.

Ecological compensation is an important economic tool for the control and management of ecological and environmental problems. The accurate assessment of the amount of compensation is the key factor in the implementation of ecological compensation schemes. However, due to the complex and various ecological and environmental problems caused by groundwater overexploitation, there is no scientific quantitative method. Emergy theory is a new method to quantitatively study the relationship between environmental resources and social economy. Based on the literature review of ecological compensation for groundwater overexploitation, this paper puts forward a new evaluation method for using emergy loss as groundwater overexploitation ecological compensation. The emergy system diagram of environmental problems caused by overexploitation of groundwater is constructed. And the calculation methods of the emergy loss of eco-environmental problems caused by groundwater overexploitation, such as land subsidence (collapse), salt water intrusion, surface runoff reduction, vegetation deterioration, and groundwater pollution, were presented, respectively. Taking Zhengzhou as an example, the total amount of ecological compensation for groundwater overexploitation in 2014 was equivalent to 853 × 106 US dollars. The largest loss of land subsidence is 816 × 106 US dollars, which accounts for 95.64% of the total loss. It can be seen that land subsidence is the most serious in the eco-environmental problems caused by overexploitation of groundwater in Zhengzhou.