The urban water ecosystem is a core foundation for the urban construction of ecological civilization. Ecosystem health is directly related to the economic development of the region and the quality of urban residents’ lives. Evaluating the health state of an urban water ecosystem is an important prerequisite for the construction of an ecologically civilized city. This study used Zhengzhou City in China as research area. Firstly, a Pressure-State-Response (PSR) model was used to construct an urban water ecosystem evaluation index system. Secondly, after analyzing the deficiency of traditional fuzzy matter-element extension model in urban water ecosystem health assessment, an improved fuzzy matter-element extension assessment model (FMEAM) was constructed by introducing the variable weight theory. Finally, using the proposed model above and the data from 2007 to 2016, this study evaluated the water ecosystem health status of Zhengzhou based on water ecosystem health integrated index (
Water is a basic element of the ecological environment and is the material basis for human survival and development [
An ecosystem is described as “a unified whole composed of biology and environment in a particular physical space of nature. In this unified system, biology and environment interact with and mutually restrict each other, and they are in a relatively stable state during a certain period” [
At present, the issue of urban ecosystem health has attracted the attention of scholars and government organizations worldwide [
As the key source of providing water, the urban water ecosystem is an important part of urban ecosystems and plays a great role in urban socioeconomic system, which provides material basis for socioeconomic development. On the one hand, the urban water ecosystem provides freshwater for human’s subsistence and meets the human needs for water [
Current academic research of the urban water ecosystem health mainly involves the restoration of urban water ecosystems [
In summary, the existing studies provide reference for this research; however, the current studies of the evaluation of urban water ecosystem still have some shortcomings. As a complex system composed of nature, society, and economy, an urban water ecosystem is a network of multiple interactions, and its health status should account for various factors in an integrated way, instead of only focusing on partial elements such as water, soil, and aquatic organisms [
A recent study shows that a truly sustainable water ecosystem management requires estimating the pressures on water ecosystems [
Zhengzhou, the capital of Henan province, is one of the most important economic cities in China. Zhengzhou is located in the lower reaches of the Yellow River and covers a total area of 7446 square kilometers, which lies between E 112°42′—114°14′ and N 34°16′—34°58′ (Figure
Location of the Zhengzhou City.
The “Pressure-State-Response” urban water ecosystem health evaluation index system was established by using the PSR model. The model covers 20 indicators and reflects the water ecosystem health conditions in Zhengzhou City. An improved FMEAM model was used to determine the
The Pressure-State-Response (PSR) model was first proposed by the Organization for Economic Co-operation and Development (OECD) and has been widely used in environmentally relevant issues [
PSR model.
Selecting evaluation indicators should follow uniform criteria and principles. Based on the principle of constructing a scientific, reasonable, and representative index, we established an index system to evaluate water ecosystem health in Zhengzhou. According to the PSR model, the indicator system mainly includes pressure subsystem (B1), state subsystem (B2), and response subsystem (B3). The indicator layer is determined by 20 indicators, after fully considering the condition of the socioeconomic development and water eco-environment in Zhengzhou. Urban water ecosystem health is a relative and dynamic concept, but it needed to determine the health standard of the evaluation index. In this study, the 20 evaluation indexes in Table
Evaluation index system of urban water ecosystem health.
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Pressure (B1) | GDP Growth Rate (P1) | % | Represents the increasing economic development pressures on urban water ecosystem [ |
Urbanization Rate (P2) | % | Represents the increasing population pressures on urban water ecosystem [ | |
The Proportion of Tertiary Industry (P3) | % | Represents the urban water ecosystem pressures from tertiary industry, such as catering industry and service industry [ | |
Water Consumption Per Unit of GDP (P4) | m3 / 10− 4 Yuan | Represents the water consumption per unit of GDP pressures on urban water ecosystem [ | |
Water Consumption of Industrial Output (P5) | m3 / 10− 4 Yuan | Represents the urban water ecosystem pressures from industrial development [ | |
Water Consumption of Eco-environment (P6) | 109 m3 | Represents the urban water ecosystem pressures from eco-environment water consumption [ | |
Household Water Consumption (P7) | 109 m3 | Represents the urban water resource pressures from household water consumption [ | |
Sewage Discharge (P8) | 109 m3 | Represents the water pollution pressures on urban water ecosystem [ | |
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State (B2) | Water Resources Amount Per Unit Area (S1) | 104 m3 · km−2 | Refers to the ratio of surface water resource quantity and the land area [ |
Per Capita Water Resources (S2) | m3 | Refers to the proportion of freshwater resource quantity and the population [ | |
Per Capita Green Area (S3) | m2 | Refers to the ratio of green area and the population [ | |
Flood Control Rate (S4) | % | Refers to the state of flood control [ | |
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Response (B3) | Sewage Treatment Rate (R1) | % | Represents the ability of sewage treatment [ |
Green Coverage Rate (R2) | % | Represents the response to quantity of water resources [ | |
River Water Quality Compliance Rate (R3) | % | Represents the ability of river water resources protection [ | |
Source Water Quality Compliance Rate (R4) | % | Represents the response to quality of freshwater resources [ | |
Rate of Wastewater up to Discharge Standard for Urban (R5) | % | Represents the response to water resource security condition [ | |
Water Functional Area Compliance Rate (R6) | % | Represents the response to water resource security condition [ | |
Rate of Water Ecosystem Project Investment to GDP (R7) | % | Represents the response to water environmental protection [ | |
Rate of Environmental Protection Investment to GDP (R8) | % | Represents the response to ecological management and protection [ |
The grade standard of evaluation index system.
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Pressure (B1) | GDP Growth Rate (P1) | % | - | ≤3 | (3, 5] | (5, 8] | (8, 10] | >10 |
Urbanization Rate (P2) | % | - | ≤30 | (30, 40] | (40, 50] | (50, 60] | >60 | |
The Proportion of Tertiary Industry (P3) | % | - | ≤30 | (30, 40] | (40, 50] | (50, 60] | >60 | |
Water Consumption Per Unit of GDP (P4) | m3 / 10− 4 Yuan | - | ≤100 | (100, 200] | (200, 300 | (300, 400] | >400 | |
Water Consumption of Industrial Output (P5) | m3 / 10− 4 Yuan | - | ≤30 | (30, 60] | (60, 90] | (90, 120] | >120 | |
Water Consumption of Eco-environment (P6) | 109 m3 | - | ≤1 | (1, 2] | (2, 3] | (3, 4] | >4 | |
Household Water Consumption (P7) | 109 m3 | - | ≤4 | (4, 6] | (6, 8] | (8, 10] | >10 | |
Sewage Discharge (P8) | 109 m3 | - | ≤4 | (4, 6] | (6, 8] | (8, 10] | >10 | |
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State (B2) | Water Resources Amount Per Unit Area (S1) | 104 m3 · km−2 | + | ≥200 | [150, 200) | [100, 150) | [50, 100) | <50 |
Per Capita Water Resources (S2) | m3 | + | ≥1000 | [750, 1000) | [500, 750) | [250, 500) | <250 | |
Per Capita Green Area (S3) | m2 | + | ≥12 | [10, 12) | [8, 10) | [5, 8) | <5 | |
Flood Control Rate (S4) | % | + | ≥95 | [95, 90) | [85, 90) | [80, 85) | <80 | |
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Response (B3) | Sewage Treatment Rate (R1) | % | + | ≥80 | [60, 80) | [40, 60) | [20, 40) | <20 |
Green Coverage Rate (R2) | % | + | ≥40 | [30, 40) | [20, 30) | [10, 20) | <10 | |
River Water Quality Compliance Rate (R3) | % | + | ≥90 | [80, 90) | [70, 80) | [60, 70) | <60 | |
Source Water Quality Compliance Rate (R4) | % | + | ≥95 | [80, 95) | [65, 80) | [50, 65) | <50 | |
Rate of Wastewater up to Discharge Standard for Urban (R5) | % | + | ≥95 | [85, 95) | [75, 85) | [60, 75) | <60 | |
Water Functional Area Compliance Rate (R6) | % | + | ≥80 | [60, 80) | [40, 60) | [20, 40) | <20 | |
Rate of Water Ecosystem Project Investment to GDP (R7) | % | + | ≥1.5 | [1, 1.5) | [0.6, 1) | [0.3, 0.6) | <0.3 | |
Rate of Environmental Protection Investment to GDP (R8) | % | + | ≥1 | [0.8, 1) | [0.5, 0.8) | [0.3, 0.5) | <0.3 |
The concept of extenics was first proposed and analyzed by Chinese scholar Cai Wen [
In the evaluation method with the fuzzy matter-element extension, the selection of weights is very important and directly affects the final evaluation result. The traditional fuzzy matter-element expansion assessment model usually uses subjective weighting methods such as expert grading and Analytical Hierarchy Process (AHP). The expert grading method is a method of assigning weight values by expert assessment of the importance of each indicator, and the AHP is a method of subjectively determining weights based on the assessment of relative importance of different indicators [
The improved fuzzy matter-element extension assessment model introduces the variable weight theory to determine the weight value of each evaluation index, so as to reduce the subjectivity. The variable weight theory is an integrated weighting method based on the theory of factor space, which is applicable to the calculation of the weight of the quantitative index [
where
The classical domain can be found:
where
where
Then relation degree matrix
Then the variable weight vector
where
where
Classification of urban water ecosystem health.
Assessment level | very sick | sick | unhealthy | sub-healthy | healthy |
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0 | (0,0.335) | [0.335,0.671) | [0.671,1) | 1 |
The indicator data from 2006 to 2007 was collected. Among them, the indicators data of
The
Figure
Figure
Trend changes of main impact indexes in pressure subsystem.
Figure
Figure
Trend changes of main impact indexes in state subsystem.
Figure
Figure
Trend changes of main impact indexes in response subsystem.
Many dimensions are involved in evaluating the health of urban water ecosystems. An index system was established to represent Zhengzhou ecosystem health based on a PSR model. The system includes three subsystems: the pressure subsystem, the state subsystem, and the response subsystem. The variable weight comprehensive model is used to determine the weight of the index. The health status of the water ecosystem in Zhengzhou City was evaluated for a 10-year period (2007-2016) by using the improved FMEAM. Overall, the water ecosystem health situation in Zhengzhou has improved; however, its water ecosystem was still in an unhealthy state from 2007 to 2016. The pressure subsystem showed a slight downward trend and remained in a sub-healthy state from 2007 to 2016. The state subsystem showed an upward trend in all years except for 2008 and 2013, and response subsystem’ health state showed an increasing trend during this period. The results of the evaluation are consistent with the actual situation.
Zhengzhou’s
(1) We need to build water-saving society in Zhengzhou and to consider the rational use of water resources to reduce pressure on water resources.
(2) We need to use water resources more rationally and improve the efficiency of water resources to reduce household water consumption and water consumption of eco-environment.
(3) We can increase the capacity to control water pollution discharge by building more sewage treatment plants and by strengthening water ecology-based environmental protection.
The finding in this research can provide reference for the urban water ecosystem management. In addition, the methods used in this research can also be available for assessing ecosystem health, river health, water security, and other areas. It is worth noting that the urban water ecosystem is an important part of an ecologically civilized city and the healthy water ecosystem is an important guarantee for an ecologically civilized city. How to make an effective assessment of ecologically civilized city’s construction effect and how to analyze the relationship between the urban water ecosystem and ecologically civilized city are the focus of future work.
The data used to support the findings of this study are included within the article.
The authors declare that there are no conflicts of interest regarding the publication of this paper.
Han Han proposed the research ideas and methods of the manuscript and was responsible for data collection and writing. Huimin Li and Kaize Zhang put forward the revision suggestions to the paper.
The research is supported by the National Key R&D Program of China (No. 2018YFC0406905), the National Natural Science Foundation of China (Project No. 71302191, No. 71801130), Foundation for Postgraduate Research & Practice Innovation Program of Jiangsu Province (No. KYCX18_0513), and Foundation for Distinguished Young Talents in Higher Education of Henan (Humanities & Social Sciences), China (No. 2017-cxrc- 023). This study would not have been possible without their financial support.