1. Introduction
In recent years, China has adopted a series of measures to accelerate the construction of an ecological civilization, as the Third Plenary Session of the 18th Central Committee of the Communist Party of China (CPC) clearly stated in 2013 “to explore the preparation of natural resource balance sheets” [
1], which marks the construction of the country’s strategic goal of putting the physical accounting and asset evaluation of natural resources into effect, improving resource conservation and utilization, and building a “beautiful China” [
2,
3]. Water is the basic natural resource for human beings and all living things to survive and develop [
4]. With the rapid development of the social economy, water resources are over-committed [
5,
6,
7], as well as the massive discharge of industrial, agriculture, and domestic sewage, due to the poor management of water resources, leading to a reduction in water quantity and the decline in water quality [
8,
9,
10]. Great attention should be paid to the problem of water resource supply could not meeting water demand, resulting in water scarcity. Almost one-third of the world’s population is experiencing a severe water scarcity crisis [
11,
12]. Therefore, it is indispensable to promote the innovative management of natural resources by grasping the quantity and quality of water resource assets in the region to lessen the contradictions between economic development and environment resources.
Water scarcity occurs when the supply of fresh water cannot meet the demand [
13]. It could result from two mechanisms: physical water scarcity, which is due to insufficient natural water resources to meet the needs of a region; and economic water scarcity, caused by poor management [
14,
15]. It is found that the latter more often leads to water scarcity according to United Nations Development Programme [
7]. People tend to turn their attention to water scarcity caused by natural forces rather than to human-induced scarcity, or any other factors [
16,
17]; the real reasons for water scarcity could be covered up. In fact, water scarcity, linked to water security, is a complex phenomenon that could be solved from social, political, meteorological, economic, and environmental perspectives [
18,
19,
20,
21]. Most of the research studies have mainly been done with engineering measures, which implies that using economic valuation techniques provides a new perspective for water resource management [
22]. Water resources, used for free or at a low price, have been exploited and utilized for a long time without any compensation, leading to increasingly scarce water resources [
23,
24]. Thus, it is urgent to evaluate the water resource value, establish a balance sheet for water resources, promote the construction of an ecological civilization, and ultimately achieve sustainable development of water resources.
At present, the method to evaluate the value of water resources is mainly carried out through certainty or uncertainty methods. The former is a group of traditional deterministic evaluation methods, including the shadow price method, supply and demand pricing model, income reduction method, marginal opportunity cost method, and computable general equilibrium (CGE) model [
25,
26,
27,
28,
29,
30]. However, the water resource value system is a complex system. Traditional classical algorithms reflect the economic value of water resources to a certain extent, but they cannot solve the complicacy and fuzziness of water resource value systems [
31]. The uncertainty evaluation method, which is mainly based on fuzzy theory, might also result in information loss [
32,
33]. Set pair analysis (SPA), dealing with the interaction between certainty and uncertainty, is suitable for cases with two or more groups from two or more perspectives [
34]. To evaluate water resources objectively and truly, we need to recognize the internal structure and take social, economic, and environmental factors into consideration [
35]. For this reason, SPA is a systematic method to deal with the uncertainty of complex problems [
36,
37] and has been gradually utilized for comprehensive evaluation of water quality and water safety [
38,
39]. In this study, the comprehensive weight, resolved with the combination of AHP and entropy weight, is applied to the set pair analysis model of water resource evaluation. This will be a more practical study and provide a positive reference for the establishment of a water resource asset evaluation system.
Accurate value accounting is a critical part of water resources research. It is of great significance in the rational allocation of water resources, improvement of water environments, and alleviation of water crises. This research focuses on the water resource assets of Wuhan City from 2013 to 2017, covering hundreds of lakes in central China, with the following aims: (1) to establish a balance sheet for physical quantities of water resources; (2) to determine an integrated index of water resource value using a combination of SPA and Triangular Fuzzy Number (TFN) methods; (3) to determine the water resource unit price by applying comprehensive weight to the improved SPA model; (4) to calculate the total value of water resources.
3. Results
3.1. Physical Accounting for Water Resources in Wuhan City
Physical accounting is a basis for water resource accounting.
Table 1 demonstrates the water resource stock as well as its changes in Wuhan City from 2013 to 2017, the data for which came from “Wuhan City Water Resources Bulletin 2013–2017” [
72]. Factors influencing water resource increases are water resources from precipitation, inflows, and water return of society. Factors influencing the decrease of water resources are water intake, evaporation, outflows, and ecological consumption for water resources, such as lakes and rivers.
The main factors resulting in the water stock changes in Wuhan City are inflows and outflows. The Yangtze River and Hanshui River run through the city with large transit flows. In 2013, water resources from precipitation were more than evaporation, while from 2014 to 2017, water resources from precipitation were less than evaporation. In the past five years, the evaporation of water resources increased annually to almost twice the amount of precipitation until 2017. The largest stock of water resources appeared in 2016, mainly owing to the largest inflows and precipitation during that year. Interestingly, the stock of water resources declined sharply in 2017, even lower than the year-beginning stock in 2013.
3.2. SPA and Calculation of the Comprehensive Evaluation Vector
Table 2 reflects the assessment system of water resource value and its comprehensive weight. According to GB3838-2002 and some related researches [
49,
55,
56,
57], the water resource value evaluation standard system was established, as shown in
Table 3, namely set A. The corresponding actual values for the indicators of the water resource value evaluation index system of Wuhan City from 2013 to 2017 are shown in
Table 4, namely set B. All data sources were derived from official statistics, such as “Wuhan Statistical Yearbook 2013–2017”, “Wuhan City Water Resources Bulletin 2013–2017”, and “Wuhan Environmental Quality Bulletin 2013–2017” [
72,
73,
77,
78].
According to the water resource value accounting index system, the AHP and entropy weight were used to calculate their subjective and objective weights, respectively. Finally, the comprehensive weight was obtained, as shown in
Table 2. Then, combined with
Table 3 and
Table 4, through Equations (3) and (4) the comprehensive evaluation matrix of water resources for Wuhan City in 2017 was calculated. Likewise, the evaluation matrix in the period of 2013–2016 was calculated. The specific comprehensive evaluation results of set pair analyses (SPA) are shown in
Table 5.
According to the results in
Table 5, the fifth level has a large proportion of the water resource value assessment levels, at about 34.27% in 2016, and even over 50% in other years.
3.3. Evaluation of Water Resource Quality
According to the comprehensive evaluation results, the specific integrated fuzzy index was evaluated by the coupling evaluation model with triangular fuzzy number method and set pair analysis. According to Equations (2)–(6), the specific integrated fuzzy index of the water resources for 2013–2017 were calculated, with values of about 3.48, 3.59, 3.49, 3.33 and 3.55, which belonged to III, IV, III, III, and IV, respectively. The water quality evaluation grades were level IV both in 2014 and 2017, although the water quality in 2017 was better than that in 2014 according to the evaluation index. It could be seen that the coupling model based on set pair analysis and triangular fuzzy numbers had high sensitivity, meaning it could reflect the degree of water pollution more comprehensively and accurately. The lowest value in 2016, 3.33, indicated that the water quality was relatively better than in other years. It could be seen that the water resource value level fluctuated less, with all values between III and IV, which means that the value evaluation grades of water resources in Wuhan City are at a level of medium to relatively low.
As seen from the results above, in general, the water quality of Wuhan City was relatively low. Although there was a significant quantity of water resources, the water quality outlook was not as optimistic. This needs to be taken seriously by relevant departments to promote sustainable water management.
3.4. Calculation of Unit Price for Stock Value of Water Resources
According to Equation (9), for 2017, the per person disposable income for inhabitants E was 38,642 RMB [
78], the yearly household water consumption C was 51.1073 m
3 [
72], the max-value for A was 3% [
35,
71], and D, the costs and normal profits for water resources, was 3.285 RMB. Thus, the upper limit for water price in 2017 was obtained, at 19.3979 RMB. According to the principle of isometric intervals, the water resource price vector results for S in 2017 were 19.3979, 14.5484, 9.6989, 4.8495, and 0. The unit price of water resources (
WLJ) in Wuhan City in 2017 was 5.9293 RMB/m
3 according to the results of
Table 5 and Equation (7). In a similar way, the unit price for water resources was 3.9405, 4.2865, 5.3049, and 7.7587 RMB/m
3 for 2013, 2014, 2015, and 2016, respectively. The results indicated that the unit water price in Wuhan City fluctuated to some extent, with a stable growth from 2013 to 2016, at almost the highest level in 2016, probably owing to the relatively high quality of water resources in that year, but declined in 2017. It could be seen that the unit price of water resources largely depends on the unity of quantity and quality.
3.5. Pollution Loss of Water Resource Assets
On the basis of previous investigations, the factors seriously impacting the quality of water resources in Wuhan City were Chemical Oxygen Demand (COD) and NH
3-N [
72]. As we can see, the actual contents of these two pollutants are shown in
Table 4, namely N1 and N2. The pollution loss parameters A and B for COD are 2799.02 and 0.83548, respectively, while they are 2118.65 and 6.1268 for NH
3-N, respectively [
79]. Thus, the pollution loss rates r
1 and r
2 of COD and NH
3-N in 2017 could be calculated as 0.99997923 and 0.064318681, respectively. According to Equation (13), the comprehensive loss rate r of water pollution was 0.9999778. The discharge of wastewater in Wuhan city in 2017 was 915 million m
3 [
77]. The water price in that year was 2.05 RMB/m
3 [
73]. Finally, the actual pollution loss could be calculated as 1.875 billion RMB for Wuhan City in 2017 according to Equation (11). In the same way, the amounts of pollution loss from 2013 to 2016 were 1.947, 2.009, 2.107, and 1.866 billion RMB, respectively.
3.6. Calculation of Value of Water Resource Assets
In 2017, based on the physical accounting presented in
Table 1, the stock of water assets D was obtained, calculated as 3911 million m
3. The unit price for the stock value of water resource
WLJ was 5.9293 RMB/m
3. The pollution loss of water resource assets was 1.875 billion RMB. Thus, according to Equation (10), the total value of water resource assets was calculated, which was 21.315 billion RMB. Similarly, we could also calculate the total asset values for the years 2013–2016 at 14.221, 14.833, 28.375, and 75.558 billion RMB, respectively; details are shown in
Table 6. The annual assets of water resources in Wuhan City fluctuate greatly. The initial change is relatively stable, and then surges in 2015 and 2016, reaching the maximum in 2016, mainly due to the large amount of rainfall, at about 75.558 billion RMB, but it slumps in 2017. The water resources assets in Wuhan were 14.221 billion RMB at the beginning of 2013, rising nearly 50% to 21.315 billion RMB at the end of 2017; the assets increased by 7.094 billion RMB.
4. Discussion
This study established the balance sheet of the stock and changes of water resource assets in Wuhan City from 2013 to 2017. Year-end stock was between 3911 and 9979 million m
3. Interestingly, the stock of water resources in Jinan ranged from 61 to 128 million m
3 from 2011 to 2015 [
56], and that of Nanjing was between 2372 and 4615 million m
3 from 2011 to 2015 [
35], which suggested that Wuhan had more abundant water resources.
From a global perspective, in order to alleviate the scarcity of water, Sustainable Development Goal 6 (SDG 6), set by the United Nations in 2015, focuses on water security and sanitation for all people [
80,
81]. The goal contains eight targets, with one or more indicators for each of them, to be achieved by 2030 [
82]. It provides support for the implementation of integrated water resource management [
83], however there is still a need for improvement [
84], for example, the gap between targets in SDG 6 and corresponding indicators [
80], as well as inequitable water agreements [
85]. Utilizing economic valuation techniques could provide a new perspective for water resource management [
22]. As there is an absence of a reasonable water price mechanism, the utilization of water resources has been seriously wasted and improperly exploited for a long time, inhibiting the sustainable development of water. Accordingly, it is necessary to study the value accounting of water resources in Wuhan City.
Fifteen indicators were selected from the three aspects, namely environment, resource, and society aspects, to establish the water resource evaluation index system. Then, we combined AHP with entropy weight to compute the integrated weight for each index, effectively solving the problem of the traditional weighting evaluation bring too subjective or absolute, which improved the stability and reliability of evaluation results and provided a reference for a water resource value accounting system. A water resource value assessment system is a complex and blurry system with integrated certainty and uncertainty. Set pair analysis, a new uncertainty theory, is different from traditional probability and fuzzy set theories. This method take full advantage of the information of the water resource evaluation system so that we can calculate the price of water resources more objectively and comprehensively. Meanwhile, the coupling model with set pair analysis and triangular fuzzy number method was used to obtain the fuzzy comprehensive index of water resources value. The results showed that the overall level of water resource value in Wuhan City was medium to low. Differing from previous studies [
35,
47], this paper demonstrates that the value of water resources is not only related to water price and water volume, but also to the water quality, leading the final total value of water resources obtained being more reliable.
Obviously, in the process of water resource accounting, the lack of uniform standards become the main obstruction. That is why the results obtained by different methods are quite different. Thus, on the basis of a deep understanding of the value connotation for water resources, as well as various value theories, the issue of how to establish a resource value theory that adapts to the requirements of modernization in order to make it suitable for environmentally sustainable management is the next crucial issue to be solved. Additionally, the total amount of water resources and related factors that are chosen to evaluate the value of water resources should be improved. A previous study has shown that groundwater is seriously polluted in the densely populated industrial and commercial areas of Wuhan City [
86]. In the future, it is of great significance to conduct more detailed and accurate research studies in order to provide practical support to decision-makers and regional managers, for example, taking groundwater as an independent and significant factor in the model, or even conducting more detailed and in-depth research studies with more agriculture information regarding kind of crops that are cultivated, the weight of surface water, and groundwater consumption as well.
5. Conclusions
To compute the total value for water resources, this research focuses on the water resource assets of Wuhan City, and the results can be outlined as follows. Firstly, this study has created a balance sheet of the stock and changes of water resources in Wuhan from 2013 to 2017. The results indicate that the water resource amounts in Wuhan fluctuated greatly, from 3911 to 9979 million m3. While the initial change was relatively stable, it rose rapidly in 2015–2016 and then fell sharply in 2017. Then, according to the results of the coupling model based on set pair analysis and triangular fuzzy method values, the water quality was optimal, at a level of medium to relatively low. An improved set pair analysis was applied which obtained unit prices from 2013 to 2017 of about 3.94, 4.29, 5.30, 7.76, and 5.93 RMB/m3, respectively, based on the index system with 15 indicators and the comprehensive weight of each index. Lastly, considering the impact of water quality on the value of water resources, the James Pollution Loss model was introduced to compute the water resource loss value, which improved the reliability of accounting results. Based on the relationship between water price, quantity, and quality, the total values of water resources in Wuhan City from 2013 to 2017 were 14.221, 14.833, 28.375, 75.558, and 21.315 billion RMB, respectively. Water resource value accounting is an innovative water resources management method, which is also conducive to the comprehensive evaluation and management of water resources, as well as the sustainable development of water.