2125 © 2021 The Authors Journal of Water and Climate Change | 12.5 | 2021
Evaluation and spatial-temporal evolution of water resources carrying capacity in Dongting Lake Basin Zhenghua Deng, Liqi Dai, Bing Deng and Xiaoyong Tian
ABSTRACT
A three-dimensional rating index system for water resources system–water environment system– Zhenghua Deng (corresponding author) Liqi Dai socioeconomic system is constructed based on data from Hunan Dongting Lake Eco-environment Xiaoyong Tian Hunan Institute of Science and Technology, Monitoring Center, Hunan Provincial Water Resources Bulletin, and Hunan Statistical Yearbook. The Yueyang, water resources carrying capacity (WRCC) of Dongting Lake Basin from 2009 to 2018 is evaluated by the China E-mail: [email protected] TOPSIS model combined with analytic hierarchy process (AHP) and entropy weight, and then the Zhenghua Deng temporal evolution and spatial distribution characteristics of the WRCC of the Dongting Lake Basin are Bing Deng Key Laboratory of Dongting Lake Aquatic Eco- analyzed. The results show that: (1) The WRCC in the Dongting Lake Basin decreases from a good level to Environmental Control and Restoration of Hunan a reasonable level during the period. Among them, the WRCC of the Ouchi River, Hudu River, and Songzi Province, Changsha, River Basins decreases significantly. (2) There are obvious spatial differences in the WRCC of the China
Dongting Lake Basin in 2018, the WRCC order is Lishui River, West Dongting Lake, Zijiang River, South Bing Deng Changsha University of Science & Technology, Dongting Lake, Yuanshui River, Xiangjiang River, East Dongting Lake, Songzi River, Hudu River, Ouchi Changsha, River, with scores of 0.586, 0.526, 0.472, 0.448, 0.416, 0.397, 0.393, 0.313, 0.306, and 0.304, respectively. China Finally, some policy recommendations for improving the WRCC of the Dongting Lake Basin are proposed. Key words | combination weight, Dongting Lake Basin, TOPSIS, water resources carrying capacity
HIGHLIGHTS
• According to the definition of water resources carrying capacity, its index evaluation system has been established. • The paper combines entropy method and TOPSIS method to comprehensively evaluate the change of water resources carrying capacity of Dongting Lake Basin during the last 10 years. • The countermeasures for coordinated development of water resources and society in the Dongting Lake Basin are proposed.
INTRODUCTION
Water is one of the important resources for the survival and important factors restricting the sustainable development development of human society. With the growth of popu- of society and the economy (Zuo & Zhang ). Water lation and development of the economy, water shortage resources carrying capacity (WRCC) is an important indi- and the deterioration of the water environment are becom- cator to characterize the state of regional water resources. ing increasingly serious and are gradually turning into Scientific measurement of regional WRCC is not only a necessary prerequisite for carrying out water resource regu- This is an Open Access article distributed under the terms of the Creative lation, but also an important basis for sustainable economic Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited and social development in the region (Song & Zhan ; (http://creativecommons.org/licenses/by/4.0/). Yang et al. , ). Comprehensive evaluation of regional
doi: 10.2166/wcc.2021.210
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WRCC helps grasp the interactive relationship between factors affecting the resource carrying capacity through the water resources and economic development, and provides principal component score. Yuan et al. () applied the theoretical support and a realistic basis for coordinating improved fuzzy comprehensive evaluation method to evalu- economic, social, and environmental development ate the WRCC in Jiangyin City. He et al. () used the (Simanjuntak et al. ). TOPSIS comprehensive evaluation method to study and ana- Research on WRCC is relatively abundant, mainly focus- lyze the dynamic changes and spatial differences of the ing on the definition, the evaluation index system, and WRCC of the Yangtze River Economic Belt from 2007 to evaluation methods of WRCC. At present, there is still no 2016. Lin et al. () applied the TOPSIS model based on consensus on the definition of WRCC. Hui et al. () the entropy weight method, analysis, and evaluation of the believed that WRCC is the water system’s largest supporting WRCC in Kubuqi desert area from 2013 to 2018, and put capacity for socioeconomic development in the region forward suggestions for improvement. during certain development stages, and emphasize the sup- The above research shows that WRCC has gradually porting role of water resources for social and economic become a research hotspot in regional economics and econ- development. Xia () believed that WRCC is the ability omic geography. In general, existing studies have produced to support population size and sustainable socioeconomic good research on the evaluation of WRCC, which has cre- development, and reflects the mutual relationship between ated strong progress concerning WRCC. However, existing water resources and social economy, which is more scienti- studies still have the following limitations. First, most of fic and reasonable. As for the evaluation index system, a the research areas for WRCC are local areas, such as the three-dimensional evaluation index system is often con- western, central, and northeastern provinces, as well as structed based on water resources–social economy– specific urban groups like the Yangtze River Delta in ecological environment (Li et al. ). A five-dimensional China. There are few studies on the comprehensive evalu- rating index system about driving force–pressure–status– ation of WRCC based on river basins. Second, the index influence–response (DPSIR) is used to evaluate WRCC system needs to be further improved. Most existing (Chen et al. ; Zhu & Wang ; Li et al. ; Weng studies adopt socioeconomic and water resource indicators et al. ). An evaluation index system from the perspec- (Rijiberman & van de Venb ; Wu et al. ), and tives of quantity–quality–watershed-flow comprehensively there is no consideration of water environment indicators evaluated the WRCC of the Beijing–Tianjin–Hebei area that affect WRCC. Third, most of the existing literature uses (Yu et al. ). In terms of quantitative research of subjective weighting such as the principal component analysis WRCC, the commonly used evaluation methods are method or objective weighting such as the entropy weighting mainly the conventional trend method, principal com- method, which may lead to insufficient accuracy of the evalu- ponent analysis method, fuzzy comprehensive evaluation ation results of WRCC. method, and system dynamics method. Cui et al. () Based on the current research work, this paper takes the adopted set pair analysis and the improved entropy weight Dongting Lake Basin as the research area. Considering method to determine the objective weight of indicators, water environment indictors’ impact on WRCC, the paper making the evaluation results more real and accurate. Qu & applies the water environment monitoring data of each Fan () used the conventional trend method to study basin monitoring point of the Ecological Environment the WRCC of the Hei River Basin as well as analyzing the Monitoring Center of Dongting Lake, and selects indicators supplyanddemandrelationshipofwaterresourcesinthe from the three subsystems of water resources, water environ- basin under different schemes. Some authors used the ment, and social economy, and then constructs a system dynamics method to establish a comprehensive assess- comprehensive evaluation index system of the WRCC. ment model of water resources in Yiwu and Xi’an (Feng et al. Finally, the program takes the TOPSIS model combined ; Haddeland et al. ). Li et al. () used the principal with composite weighting based on the improved analytic component analysis method to comprehensively evaluate the hierarchy process (AHP) and entropy value method to deter- resource carrying capacity of Zhengzhou and found the main mine the comprehensive weight of each indicator, and the
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temporal and spatial dynamic changes of WRCC in the and Hunan Dongting Lake Ecological Environment Dongting Lake Basin from 2009 to 2018 are evaluated. Monitoring Center obtained water resources data and socio- The remainder of this paper is organized as follows. The economic data. Ten representative Dongting Lake Basin next section introduces the study area and data source, fol- monitoring stations (Figure 1) were screened to obtain the lowed by a section describing the research methods. Then, water environment data, and included: S1 Songzi River’s a section presents the empirical research results and the Xinjiangkou; S2 Hudu River’s Mituo Temple; S3 Oujichi final section discusses the research findings and concludes River’s Butler Shop; S4 Xiangjiang’s Zhuting Town; S5 the study. Zijiang’s Pingkou; S6 Yuanshui’s Guanyin Temple; S7 Shi- menxinguan of Lishui; S8 Yueyang Tower in the east of Dongting Lake; S9 Xiaohezui in the west of Dongting STUDY AREA AND DATA SOURCE Lake; and S10 Hengling Lake on the south bank of Dongt- ing Lake. Study areas
The Dongting Lake Basin is located in the northeast of Hunan RESEARCH METHODS Province, on the south bank of the Jingjiang River in the middle reaches of the Yangtze River, forming a complex inter- Evaluation index system action relationship with the Yangtze River. The Ouchikou, Songzikou, and Taipingkou (referred to as ‘Three Outlets’)to According to the definition of WRCC and the principles of the north divert the Yangtze River water from the Oujichi comprehensiveness, representativeness, comparability, and River, Songzi River, and Hudu River into Dongting. Xiang- data availability of the evaluation index system, this paper jiang, Zijiang, Yuanjiang, and Lishui (referred to as the ‘Four constructs the three-dimensional indicator system of water Rivers’) come from the south and are injected into the Dongt- resources system, water environment system, and social ing Lake and, after being stored in the lake, the water system economic system. The water resource system includes four flows through Yueyang City into the Yangtze River. Dongting indicators: water resources per capita, water production Lake is an important throughput lake in the Yangtze River modulus, river patency, and average annual runoff. The Basin. With the advancement of industrialization, farming water environment system includes total water phosphorus modernization, and urbanization in the lake area, the relation- content (TP), total water nitrogen content (TN), chemical shipbetweentheYangtzeRiverandDongtingLakeevolved oxygen demand (COD), and water dissolved oxygen content after the Three Gorges Project became operational. The (DO). The socioeconomic system includes urban population water resource shortage and worsened water resource environ- density, urbanization rate, regional GDP, 10,000 industrial ment has evolved into the restricted condition of Dongting value-added water consumption and 10,000 agricultural Lake regional economic development. As such, studying the value-added water consumption. Table 1 shows the selection spatiotemporal evolution of the WRCC of the Dongting of specific indicators and their impact on WRCC. Lake Basin is of great significance for solving the contradiction between the supply and demand of water resources. It also promotes the sustainable use of water resources and creates Composite weighting theDongtingLakeeco-economiczoneandthegreendevelop- ment demonstration zone. In order to accurately reflect the weights of the indicators of the water resources system, water environment system, and Data sources socioeconomic system of Dongting Lake Basin’s WRCC, this paper combines with subjective weighting by AHP Based on Dongting Lake Basin from 2008 to 2019, Hunan and objective weighting by entropy weighting method to Statistical Yearbook, Hunan Water Resources Bulletin, determine the weight.
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Figure 1 | Distribution of Dongting Lake Basin and monitoring points.
AHP was proposed by the American scholar A. L. Saaty corresponding eigenvector of the judgment matrix can (). It introduces the experience and professional knowl- be obtained. edge of decision-makers into the evaluation process to (iii) The third step is the consistency test. When the consist- determine the subjective weight of each evaluation index. ency ratio CR <0.1, it shows that the judgment matrix The specific calculation steps are presented: has passed the consistency test, and after normaliza- tion, the weight of each index is obtained. ¼ (i) the judgment matrix U ((auv)m×m), where auv is the relative importance of index u compared with indicator Compared with the AHP, the entropy weight method v, and its value range is 1–9. can objectively determine its weight based on the infor- (ii) The second step is to calculate the maximum eigenvec- mation provided by each evaluation index, to avoid the tor of the judgment matrix. According to the formula deviation of the results caused by the randomness of subjec-
Uw ¼ λmaxw, the maximum eigenvalue λmax and tive weighting, where the entropy weight can measure the
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Table 1 | Evaluation index system of water resources carrying capacity of Dongting Lake
Index Target layer Criterion layer Index layer Index description properties
Water resources Water resources C1 Water resources per capita Total water resources/Total population (m³/Per) Benefit carrying capacity system C2 Water production modulus Total water resources/Total area (104 m³/km²) Benefit C3 Rivers fluidity Annual average time of river cut off/day Cost C4 Annual average runoff Statistical data (m³) Benefit Water environment C5 Total phosphorus TP (mg/L) Cost system C6 Total nitrogen TN (mg/L) Cost C7 Chemical oxygen demand COD (mg/L) Cost C8 Dissolved oxygen DO (mg/L) Benefit Social economic C9 Urban population density Urban population/Total area (people/km²) Cost system C10 Urbanization rate Urban population/Total population (%) Benefit C11 Gross domestic product GDP statistical data (/billion yuan) Benefit C12 Water use for generating Industrial water consumption/Industrial value- Cost every 10,000 yuan in added (m³/yuan) industrial value added C13 Water use for generating Agriculture water consumption/Agriculture Cost every 10,000 yuan in value-added (m³/yuan) agriculture value added
degree of disorder of the system, that is, the smaller the information entropy of a set of data is as follows: information entropy of the indicator, the larger the entropy Xn weight, that the indicator is more important, and vice versa. 1 H ¼ f ln f i lnn ij ij The main calculation steps are as follows: j¼1 r (i) Data standardization. Construct the original data matrix: ¼ ij fij Pn (2) Z ¼ (zij) × . Due to the different dimensions and index m n rij attributes of the data, the data will be standardized j¼1 using a standardized method: (iii) fij is the characteristic proportion of the indicator. fi Normalized formula for bene t indicators: Therefore the weight of each indicator is
1 H rij ¼ zij min (zij)=max (zij) min (zij) ¼ i Wi Pm (3) m Hi i¼1 Normalized formula for cost indicators: (iv) Upon determining the weights of the indicators, we established an indicator weighted criterion matrix using rij ¼ max (zij) zij=max (zij) min (zij) (1) the following formula:
¼ The normalization matrix R (rij)m×n is obtained, where Y ¼ rij × Wi (4) rij is the normalized value of the i-th index at the j-th moni- toring point; and max (zij) and min (zij) represent the TOPSIS model maximum and minimum values of the i-th target at the j-th
observation point. Technique for order preference by similarity to an ideal sol- (ii) Calculation indicator weights. According to the defi- ution (TOPSIS) is one of the methods for comprehensive nition of information entropy in information theory, the evaluation of multi-objective decision-making. The basic
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idea is to detect the relative distance between the evaluation the research results of many scholars, the final calculation index and the optimal and the worst solutions. To sort, the result T is divided into five levels representing severe over- concept is clear and operable, and it can be used for hori- load, overload, reasonable, good, and high quality of zontal and vertical comparative analysis. Specific WRCC, as shown in Table 2. evaluation steps are as follows:
(i) Calculate relative distance. We calculated the ideal sol- ution Y þand the negative solution Y of the indicator EMPIRICAL RESEARCH RESULTS weighted criterion assessment value using formula (5): Calculation results þ Y ¼{ max yi1, max yi2 ...max yim} (5) Y ¼{ min yi1, min yi2 ...min yim} According to the calculation steps of combination weight- ing, the weights of each index are calculated by formulas (1)–(4). The specific results are shown in Table 3. The distance from the i-th index to the optimal solution According to the calculation results of the combined Y þ is recorded as Dþ. The distance from the i-th index to the j weights, using formulas (5) and (6), the evaluation results negative ideal solution Y is recorded as D , and the calcu- j of the WRCC of each basin can be calculated as shown in lation formula is as follows: Table 4. vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi u uXm þ ¼ t 2 Dj ( max yij yij) Analysis of temporal evolution of water resources i¼1 carrying capacity in Dongting Lake Basin vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi u uXm ¼ t 2 During the inspection period, the average WRCC of the Dj ( min yij yij) (6) i¼1 entire basin of Dongting Lake decreased from 0.472 in 2009 to 0.415 in 2018 (Figure 2). Among them, the WRCC of the Dongting Lake district decreased from 0.509 in (ii) Calculate the relative closeness of each assessment þ 2009 to 0.456, from a good level to a reasonable level, show- indicator value vector to the ideal solution Y using ing a steady decline in general. The average value of Three formula (7): Outlets Basin declined from 0.413 in 2009 to 0.305 in