Evaluation of regional water resources carrying capacity based on binary index method and reduction index method

Hong-yun Fng , Sheng-wei Gn , Chen-ying Xue

a College of Hydraulic Science and Engineering, Yangzhou University, Yangzhou 225009, China

b Taihu Lake Basin Hydrological and Water Resources Monitoring Center, Wuxi 214024, China

Abstract Based on the regional water resources carrying capacity(WRCC)evaluation principles and evaluation index system in the National Technical Outline of Water Resources Carrying Capacity Monitoring and Early Warning (hereafter referred to as the Technical Outline), this paper elaborates on the collection and sorting of the basic data of water resources conditions,water resources development and utilization status,social and economic development in basins,analysis and examination of integrity,consistency,normativeness,and rationality of the basic data,and the necessity of WRCC evaluation.This paper also describes the technique of evaluating the WRCC in prefecture-level cities and city-level administrative divisions in the District of the Taihu Lake Basin, which is composed of the Taihu Lake Basin and the Southeastern River Basin.The evaluation process combines the binary index evaluation method and reduction index evaluation method.The former,recommended by the Technical Outline,uses the total water use and the amount of exploited groundwater as evaluation indices,showing stronger operability,while the latter is developed by simplifying and optimizing the comprehensive index system with greater systematicness and completeness.The mutual validation and adjustment of the results of the above-mentioned two evaluation methods indicate that the WRCC of the District of the Taihu Lake Basin is overloaded in general because some prefecture-level cities and city-level administrative divisions in the Taihu Lake Basin and the Southeastern River Basin are in a severely overloaded state.In order to explain this conclusion,this paper analyzes the causes of WRCC overloading from the aspects of basin water environment, water resources development and utilization, water resources regulation and control ability, water resources utilization efficiency, and water resources management.

Keywords:Water resources carrying capacity (WRCC); Evaluation; Binary index method; Reduction index method; Prefecture-level cities and city-level administrative divisions

1.Introduction

With the stable and rapid development of China's social economy, the tension between water resources constraints,which arises from a contradiction between a large population and scarce water resources with uneven spatiotemporal distributions, and economic and social development has become increasingly severe.In response to the worrisome state of China's water security,measures should be taken to promote sustainable utilization of both water resources and economic and social development.TheOverall Plan of Ecological Civilization System Reform(SCPRC, 2015)made it clear that equilibrium should be sought in China's territorial space.In other words, an appropriate balance should be found between population, economy,resources,and the environment to boost development, and the population, industrial structure, and economic growth of a region should not surpass its environmental capacity and the carrying capacity of its water and land resources.This requires quick establishment of monitoring and early warning mechanisms throughout the country in order to implement restraint measures in regions where water and land resources, environmental capacity, and marine resources are overloaded.Therefore, in March 2016, the Ministry of Water Resources of the People's Republic of China issued theNotice on Preparing for the Establishment of Water Resources Carrying Capacity Monitoring and Early Warning Mechanisms Across the Country(MWRPRC,2015a),and formulated theNational Technical Outline of Water Resources Carrying Capacity Monitoring and Early Warning(hereafter referred to as the Technical Outline)(GIWRHPDMWR, 2016), which defined the method for calculating water resources carrying capacities (WRCCs)and water resources carrying loads(WRCLs), a method for evaluating water resources carrying status, and related technical requirements.

In accordance with theNotice on Carrying out the Pilot Work on Establishing Monitoring and Early Warning Mechanisms for Water Resources Carrying Capacity(MWRPRC,2015b), WRCC evaluation has been completed in all river basins across the country, a move toward establishing basinwide WRCC monitoring and early warning mechanisms for prefecture-level cities, city-level administrative divisions, and counties located in the basins.The specific evaluation measures are as follows:a thorough investigation of the economic state and development of the area and the state as well as utilization of its water resources; a summary analysis of basic information regarding the state of basin water resources to determine basic WRCC conditions; the calculation of economic and societal WRCLs;the evaluation of water resources carrying status and analysis of water resources overloading causes;and the establishment of appropriate control measures.These evaluation measures provide the necessary information for establishing a WRCC monitoring and early warning mechanism for each basin and forming a long-term mechanism of WRCC-based planning and development.Based on the evaluation work for the District of the Taihu Lake Basin,this paper describes the application of the binary index method and reduction index method to WRCC evaluation for prefecture-level cities and city-level administrative divisions in this district.

2.Evaluation method

2.1.Collection, sorting, and examination of basic data

2.1.1.Collection of basic data

The following information was collected and sorted:(1)information related to the National Water Resources Comprehensive Planning, comprehensive planning for water resources completed by related basin management organizations, medium- and long-term planning for water supply and demand in river basins, and the First National Water Census;(2)statistical yearbooks and water resources bulletins of administrative divisions in the basins with similar timelines to the target year;and(3)technical results and statistics,such as those regarding interim measures for assessing the implementation of the most stringent water resources management system, and the measurement and analysis results of the effective utilization coefficient of farmland irrigation water in all provinces.Based on all the collected information, economic and social development indices(such as the population,GDP,and irrigated area)and indices related to water resources and their development and utilization(such as the total amount of water resources, water supply, water use, water consumption,and water discharge)for the basins in the target year were summarized and examined.

2.1.2.Examination and rationality analysis of basic data

Basic WRCC data reported by the administrative divisions in the Taihu Lake Basin were compared with related statistical data such as the issued statistical yearbooks and water resources bulletins.Various methods such as the trend method,quota method, and correlation analysis method were used to examine and analyze the integrity, consistency, normativity,and rationality of the basic data reported by each province(or municipality).Then, the final data results used for the WRCC evaluation of the prefecture-level cities and city-level administrative divisions in the basins were determined.

2.2.Evaluation scope

The WRCC evaluation covered the entire District of the Taihu Lake Basin, including two types of units:prefecturelevel cities and city-level administrative divisions.

2.3.Regional WRCC evaluation methods

2.3.1.Method of evaluation according to Technical Outline

The overall technical path is as follows:(1)decomposing and examining the total water use control index of provinces and cities in the basins according to the relevant requirements in the Technical Outline;(2)examining the groundwater exploitation control index;(3)determining the WRCC and WRCL of each province and city in the district; (4)evaluating the water resources carrying status of the basins, especially of the prefecture-level cities and city-level administrative divisions;and(5)determining the corresponding evaluation results.

2.3.1.1.Water quantity evaluation indices and identification criteria

(1)Evaluation indices

According to the definition of WRCC in the Technical Outline (GIWRHPDMWR, 2016)and the principles of operability, measurability, and monitorability, the indices defined by the “three red lines” for the most stringent water resources management were used as references for the index selection in this study.The total water use and the amount of exploited groundwater were selected as indices for evaluating the WRCC of the basins, i.e., the binary index method was used.

The total water use index:The red lines of water resources development and utilization of various provinces and cities that have been promulgated in the implementation plan or evaluation method of the most stringent water resources management system at all governmental levels were selected as the total water use index for calculating the WRCC of prefecture-level cities and city-level administrative divisions in the basins.

The groundwater exploitation index:According to the results of water resources surveys and evaluations and of groundwater utilization and protection planning, the control index for groundwater exploitation, or the amount of groundwater available, was used as the groundwater exploitation index for calculating WRCCs.In regions where the amount of exploited groundwater was greater than that of groundwater available in the target year,the latter was used as the groundwater exploitation index; in regions with surplus available groundwater, the control amount of exploited groundwater was used as the groundwater exploitation index.

(2)Identification criteria

According to the binary index identification criterion,single-factor evaluation was performed for the WRCC of the basins using real physical indices.The water resources carrying status was directly identified in reference to the measurement criteria of the physical quantity indices.For hilly areas,considering that groundwater resources are basically the same as surface water resources, the amount of exploited groundwater was regarded as surface water and was not evaluated separately.The evaluation criteria of the binary index method for analyzing the water resources carrying status are expressed by Eq.(1):

whereW0is the total water use andG0is the amount of exploited groundwater in plain areas, which represent the regional WRCC baselines; andWandGrepresent the actual total water use and amount of exploited groundwater, respectively.For plain areas, ifG0≤G＜1.2G0, the shallow groundwater over-exploitation coefficient of super-mining areas was in the range of (0,0.3), or, for hilly areas, there was overexploitation of groundwater and the amount of exploited groundwater was considered to be overloaded.IfG≥1.2G0,the shallow groundwater over-exploitation coefficient of supermining areas was higher or equal to 0.3, or there was deep confined water exploitation or over-exploitation of groundwater in hilly areas, and the amount of exploited groundwater was considered to be severely overloaded.

The water resources carrying status was evaluated based on the total water use and the amount of exploited groundwater in the selected years.In each case, the most unfavorable evaluation index was used for identification.That is, if one index was overloaded and the other was severely overloaded, the case was taken as severely overloaded; if one index was overloaded and the other was nearly overloaded, the case was taken as overloaded.The identification criteria were as follows:(1)severely overloaded:either evaluation index was severely overloaded; (2)overloaded:either index was overloaded; (3)nearly overloaded:either index was nearly overloaded;and(4)non-overloaded:neither index was overloaded.

2.3.1.2.Water quality evaluation indices and identification criteria

(1)Evaluation indices

Two indices were selected for evaluating water quality:the water quality compliance rate of water function zones in the current year, and the amount of pollutants entering the rivers.

(2)Identification criteria

The water quality compliance rate (Q)and water quality compliance rate control index(Q0)of water function zones in the prefecture-level cities were compared, and the amount of pollutants entering the rivers (P)and the pollutant discharge limit (P0)were compared as well.The identification criteria are shown in Eq.(2):

The water quality of prefecture-level cities and counties was evaluated based on the criteria above.

2.3.1.3.Comprehensive evaluation of water resources carrying status

The water resources carrying status was comprehensively evaluated based on the water quantity and quality evaluation results.The identification criteria were as follows:(1)severely overloaded:water quantity and/or quality was severely overloaded; (2)overloaded:water quantity and/or quality was overloaded; (3)nearly overloaded:water quantity and/or quality was nearly overloaded; and (4)non-overloaded:neither water quantity nor quality was overloaded.

The water resources carrying status of prefecture-level cities and city-level administrative divisions was evaluated using the above-mentioned evaluation methods.The rationality of the evaluation results was analyzed based on regional water resources conditions, water resources development and utilization status, and economic and social development conditions and trends.

2.3.2.Reduction index method

A lot of research has been carried out on the WRCC evaluation index system(Dou et al.,2015;Hu et al.,2016;Jia et al., 2018; Li, 2010; Li et al., 2011; Sandoval-Solis et al.,2011; Wang et al., 2005, 2019; Xu et al., 2013; Yang et al.,2019;Zhang et al., 2013),and all index systems proposed are standard to some extent.These index systems are characterized by clear hierarchies and high integrity and play a guiding role in selecting WRCC evaluation indices(Wang et al.,2017;Zhang et al., 2019a, 2019b).However, their composition is often complicated, the data necessary for some indices are difficult to obtain, and the statistical time scales of some indices are not uniform, making it difficult for the index systems to meet the dynamic WRCC evaluation requirements(Wu et al., 2018).Thus, they are not practical for earlywarning WRCC applications and must be simplified.This study first carried out a sensitivity analysis to roughly simplify multiple comprehensive index systems.That is, a vector model was used to characterize the relative WRCC strength,and then a sensitivity analysis was used to quantitatively evaluate the responses of WRCCs to changes in various indices to identify and remove indices with low sensitivities.The remaining indices were then accurately screened through cluster analysis to establish a set of regional WRCC (dynamic)evaluation index systems that were rational, feasible,and easy to operate.

(1)Vector model WRCC representation

Integrating the existing implications of WRCC, this study defined WRCC as the socio-economic scale and population size with a certain standard of living that can be supported by the water resources of a certain region in a certain historical period after rational optimization of water resources allocation based on foreseeable socio-economic, scientific, and technological development levels, sustainable development, and environmental preservation.In order to quantify the WRCC for the reduction analysis, the carrying capacity connotation used for calculating the WRCC sensitivity was represented by a vector model.

Assumingmdifferent target years ormdifferent regions in the same target year,there weremcarrying capacity evaluation values, which were denoted as Ej（j= 1,2,…,m）.Assuming that eachEjincluded the components ofnspecific indices,i.e.,Ej= （E1j,E2j,…,Enj）, the weight of theith index of thejth carrying capacity waswij, which was denoted asafter index standardization.Therefore, the evaluation value of thejth carrying capacity can be expressed by the following standardized vector model:

(2)Sensitivity analysis and dynamic cluster analysis for evaluation index selection

The sensitivity coefficients were calculated using Eq.(5).Based on the calculation results, the sensitivity levels were classified to quantitatively evaluate the characteristics of the WRCC sensitivity to the influencing factors, i.e., the WRCC responses to changes in its influencing factors (Guo et al.,2015):

where β is the sensitivity coefficient;ItandIt+1represent the WRCCs in different periods; andLtandLt+1represent the influencing factors in different periods(indicated by the actual value of each evaluation index).The control variable method was used to calculate the sensitivity coefficient of each index towards the WRCC.The larger the value of β, the higher the sensitivity of the WRCC to the change in the evaluation index,i.e.,a small change in the evaluation index could cause a large fluctuation in the WRCC.

The data set was retained after the sensitivity analysis was investigated with statistical product and service solutions(SPSS)statistical software for dynamic cluster analysis.Specifically, the correlation coefficients between evaluation indices were calculated, and then the listed indices were clustered with the correlation coefficients (Wang et al.,2017).We setrijas the correlation coefficient between theith index andjth index,xkjas the value of thejth index standardized for thekth evaluation object (k= 1,2,…,m),andas the average value of thejth index.The correlation coefficient between evaluation indices is given by the following equation:

The analysis steps are as follows:

(a)Establishing a correlation matrix, finding the largest correlation coefficientXij, and clustering theith andjth samples into one class.Then, removing theith row and thejth column from the matrix, finding the largest correlation coefficient in the new matrix, and clustering the corresponding samples (the preceding procedure was repeated cyclically).

(b)Removing the first index and repeating step 1 to obtain the sample clustering result.Then,removing the second index to thenth indices sequentially for the correlation analysis and sample clustering (this procedure was repeated by removing one index each time)to obtain the clustering results of all the samples.

(c)Comparing the clustering results after removing each index and the comprehensive index clustering result.If the results were the same, the index had no significant effect on the classification of evaluation samples,and the index could be deleted.Otherwise, the index was retained.

(3)WRCC evaluation using set pair method

The set pair evaluation method, characterized by a simple structure and clear concept, can succinctly calculate the evaluation results.If the values of indexxlof the evaluation samples are regarded as set Aland the evaluation criteria of the index are regarded as another set Bk, then they can constitute a set pair（Al, Bk）.For a set pair of two given sets H = （A,B）, the characteristics of set pair H were analyzed in the context of a specific problem.A total ofNcharacteristics were obtained,among which sets A and B in the set pair H hadScharacteristics in common andPcharacteristics that were opposite.The remainingF=N-S-Pcharacteristics were neither opposite nor in common.The correlation degree μ can be expressed by

According to the principle of set pair analysis, the relationship of the set pair （Al,Bk）, wherek= 1,2,…,K, can be described by theK-member correlation degree μl.The method of calculating the correlation degree was determined according to the classification standard of the evaluation indices (Wang et al., 2009).

3.Case study

3.1.Study area

The District of the Taihu Lake Basin, composed of the Taihu Lake Basin and the Southeastern River Basin, covers most of the southern area of Jiangsu Province, most of Shanghai City, Zhejiang Province, and Fujian Province(except the Poyang Lake Basin and Hanjiang River Basin),and parts of Huangshan and Xuancheng in Anhui Province,with a total area of 2.452 × 105km2.The evaluation in this study was carried out for the District of the Taihu Lake Basin,specifically 28 prefecture-level cities and city-level administrative divisions in the above-mentioned four provinces and one municipality directly under the central government.

The Taihu Lake Basin is located in the central part of China's coastal area and at the southern end of the Yangtze River Delta.The basin is slightly triangle-shaped, reaching the Yangtze River to the north,the East China Sea to the east,the Qiantang River to the south,and the Tianmu,Jieling,and Maoshan mountains to the west.The drainage area is 36895 km2.The administrative divisions belong to Jiangsu,Zhejiang, Shanghai, and Anhui.In 2015 (the target year for evaluation), the permanent population of the Taihu Lake Basin was 59.967 million, with a total GDP of 6688.39 billion CNY.The ratio of primary, secondary, and tertiary industries was 2:41:57,the total area of cultivated land in the basin was 11688 km2, and the effective irrigation area was 98409 km2.The Taihu Lake Basin has a subtropical monsoon climate with four distinct seasons and abundant rainfall and heat.According to theComprehensive Planning of Water Resources of the Taihu Lake Basin and the Southeastern River Basin Water Resources(Taihu Basin Authority, 2011),the average annual precipitation of the Taihu Lake Basin from 1956 to 2000 was 1177.3 mm, and approximately 60%of the precipitation was concentrated in the flood season from May to September.The average annual water surface evaporation was 822 mm,with a variation range of 750-900 mm.The average annual natural runoff was 16.01 billion m3, and the number of annual average rainy days was 140-160.Affected by the atmospheric circulation, the precipitation in the basin varies greatly from year to year and is unevenly distributed.

The Southeastern River Basin is located in the southeastern coastal area of China and possesses a relatively developed economy and abundant water resources.It includes three provincial administrative divisions, i.e., Zhejiang,Fujian, and Anhui, with a drainage area of 2.083 ×105km2.The basin is mainly mountainous and hilly, with the hilly areas accounting for 90% of the total area.There are many topographic basins and, except for a few small plains in the lower reaches of a few rivers,most areas are lofty mountains,undulating hills,scattered valleys,and topographic basins.In 2015, the Southeastern River Basin had a permanent population of 80.5704 million and a GDP of 5696.43 billion CNY.The ratio of primary, secondary, and tertiary industries was 6:49:45.The total area of cultivated land in the basin was 25763 km2.The basin has a subtropical maritime monsoon climate with high temperatures and humidity.Rainfall and heat occur together over the same period, causing abundant water vapor,and monsoons cause clear seasonal changes.The annual average temperature is between 15°C and 21°C,increasing from north to south.There are many rivers in the basin that are generally short, swift, and self-contained, and flow into the sea separately.According to theComprehensive Planning of Water Resources of the Taihu Lake Basin and the Southeastern River Basin Water Resources(Taihu Basin Authority, 2011), the average annual precipitation of the Southeastern River Basin was 1662.4 mm,and approximately 72%of the annual precipitation was concentrated in the flood season from April to September.The spatial distribution of precipitation is influenced by the climate, water vapor, and topography.The precipitation generally increases from 1200 to 1400 mm in the southeastern coastal areas to over 2000 mm in the northwestern mountainous areas.The precipitation varies greatly from year to year,and its distribution is uneven.

3.2.Evaluation of regional water resources and their development and utilization status

3.2.1.Water resources

(1)Quantity of water resources

In 2015,the total amount of water resources in the District of the Taihu Lake Basin was 329.643 billion m3,of which the surface water resources reached 324.16 billion m3and groundwater resources reached 65.715 billion m3.The amount duplicated between surface water and groundwater was 60.232 billion m3, and the average water production modulus of the basin was 1.1622 × 106m3/km2.The water production coefficient was 0.79.

The annual runoff in the Taihu Lake Basin is mainly recharged by precipitation,which is similar to the precipitation distribution but more uneven.It is concentrated in the flood season and is unevenly distributed across the four seasons,with large differences between the maximum and minimum monthly runoffs.According to the evaluation results of related water resources investigations, the annual average total amount of water resources in the Taihu Lake Basin from 1956 to 2000 was 17.736 billion m3, the annual average surface water resources reached 16.145 billion m3, and the average water production modulus of the whole basin was 4.807 × 105m3/km2.In 2015, the total amount of water resources in the Taihu Lake Basin was 34.24 billion m3, of which the surface water resources reached 31.16 billion m3and groundwater resources reached 5.93 billion m3, and the average water production modulus of the whole basin was 9.28×105m3/km2.The river runoff in the Southeastern River Basin is mainly recharged by precipitation, with large interannual variations.According to the evaluation results of related water resources investigations, the total annual water resources of the Southeastern River Basin from 1956 to 2000 was 199.226 billion m3, of which the average surface water resources reached 198.47 billion m3and the average groundwater resources reached 52.04 billion m3.The average water production modulus of the whole basin was 9.565 × 105m3/km2.In 2015, the total amount of water resources of the Southeastern River Basin was 256.24 billion m3,of which the surface water resources reached 253.54 billion m3and groundwater resources reached 55.39 billion m3.The average water production modulus was 1.223 million m3/km2.

(2)Quality of water resources

According to the water quality monitoring statistics and evaluation results for the Taihu Lake Basin and Southeastern River Basin, 614 water function zones in the District of the Taihu Lake Basin participated in the all-factor evaluation,44.5% of which complied with the quality standards.In the Taihu Lake Basin, 380 function zones participated in the allfactor evaluation, 27.9% (106)of which complied with the quality standards.The compliance rate of Level-I water function zones was 24.5%, while that of Level-II water function zones was 29.0%.Of the participating function zones in the Taihu Lake Basin, the length of rivers complying with the quality standards was 1361.2 km, with a compliance rate of 30.7%.The area of lakes complying with the quality standards reached 41.1 km2, with a compliance rate of 2.2%.In 2015, 234 water function zones in the Southeastern River Basin participated in the all-factor evaluation, 71.4% (167)of which complied with the quality standards.The compliance rate of Level-I water function zones was 80.0%, while that of Level-II water function zones was 68.7%.Of the participating function zones in the Southeastern River Basin, the length of rivers complying with the quality standards was 3260 km,with a compliance rate of 68.2%.The area of lakes complying with the quality standards reached 986.4 km2, with a compliance rate of 90.1%.

3.2.2.Water resources development and utilization

In 2015, the total water supply of the city-level administrative divisions in the District of the Taihu Lake Basin was 77.361 billion m3,as shown in Table 1.The total water use of 2015 in the District of the Taihu Lake Basin was 77.361 billion m3, as shown in Table 2.Industry-specific water usage accounted for the largest amount, followed by agricultural,domestic, and ecological water use.In 2015, the total water consumption of various industries in the Taihu Lake Basin was 34.732 billion m3, with a comprehensive water consumption rate of 44.9%, as shown in Table 3.

3.3.Evaluation technique

In this study, the Technical Outline-based evaluation method and reduction index evaluation method were combined to evaluate the WRCCs of prefecture-level cities and city-level administrative divisions in the District of the Taihu Lake Basin.That is, the results of the reduction index method were used to verify and adjust the WRCCs obtained by the Technical Outline-based evaluation method to comprehensively determine the WRCCs.

With limited basic conditions of water quality evaluation materials, this study used the two water amount evaluation indices to evaluate the water resources carrying status.As mentioned above,the WRCC and WRCL of each province and city in the District of the Taihu Lake Basin were calculated and analyzed through decomposition and examination of the total water use control index for the provinces and cities as well as examining the groundwater exploitation control index.Then, the discriminant criteria shown in Eq.(1)were used to evaluate the water resources carrying status of the district in two groups, prefecture-level cities and city-level administrative divisions, to obtain the corresponding evaluation results.

According to the reduction index method procedure, the actual water supply and demand conditions, economic and social development, and water resources development and utilization in the study area were evaluated first.The current standard comprehensive index system (Ait-Aoudia and Berezowska-Azzag, 2016; Dou et al., 2015; Guo et al.,2015)was preliminarily simplified in a targeted manner by removing indices for which data was highly difficult to obtain,indices with uniform statistical time scales, and indices with poor representativeness.A WRCC evaluation index set for the District of the Taihu Lake Basin was established,including 29 indices related to the water resources system, social system,economic system, and ecosystem.The analytic hierarchy process and entropy weight method were jointly used to determine the weight of each index.Then, sensitivity analysis and dynamic cluster analysis were employed to reduce and optimize the above-mentioned evaluation index system.Nine indices were determined to quantify the WRCC of each prefecture-level city and city-level administrative division,including precipitation (IE2); water resources development and utilization rate (IE3); water storage capacity of large andmedium-sized reservoirs (IE5); natural population growth rate(IE9); residential water use (IE10); irrigation water quota(IE21);forestry,animal husbandry,fishery,and livestock water use (IE23); industrial water use (IE24); and ecological water recharge (IE26).After validation and analysis, it was shown that the nine indices could objectively reflect the regional WRCC from the perspectives of water resources, society,economy, and ecology.Finally, the set pair analysis method was used to evaluate the WRCC.The evaluation criteria were determined in correspondence with the Technical Outline evaluation principle and in reference to the relevant research results.WRCCs were mainly divided into four levels:nonoverloaded (Level 1), nearly overloaded (Level 2), overloaded (Level 3), and severely overloaded (Level 4).

Table 1 Total water supply of District of Taihu Lake Basin in 2015.

Table 2 Total water use of District of Taihu Lake Basin in 2015.

Table 3 Water consumption of District of Taihu Lake Basin in 2015.

3.4.Evaluation results

3.4.1.Analysis of degree of water resources development and utilization

(1)Total water use

The total water use evaluation results of the city-level administrative divisions in the District of the Taihu Lake Basin in 2015 showed that Shanghai had the largest total water use,which was 10.17434 billion m3.The total water use in Zhoushan was the least, at 215.76 million m3.A comparison of the total water use in the administrative divisions is shown in Fig.1.

(2)Amount of exploited groundwater

Statistics show that, in 2015, the amount of exploited groundwater in city-level administrative divisions in the District of the Taihu Lake Basin was 824.86 million m3,of which the exploited shallow groundwater was 815.47 million m3and exploited deep confined water was 9.39 million m3.The amount of exploited shallow groundwater was the largest(271 million m3)in Quanzhou and the smallest(0.12 million m3)in Jiaxing.The amount of exploited deep confined water was the largest (4.57 million m3)in Jinhua, followed by Shanghai(4.3 million m3).The groundwater exploitation of city-level administrative divisions in the District of the Taihu Lake Basin in 2015 is shown in Fig.2.

(3)Degree of water resources development and utilization

According to the water resources development and utilization data of the prefecture-level cities in the Taihu Lake Basin and the Southeastern River Basin in 2015,the degree of water resources development and utilization of each province(city)in the District of the Taihu Lake Basin was calculated.The summary analysis showed that the amount of developed and utilized water resources was 12.13 billion m3in Jiangsu Province and 6.87 billion m3in Shanghai, and the amount of water diverted from the Qiantang River was 510 million m3in Zhejiang Province.The total local water supply of 2015, total annual average water resources, and development and utilization rate of local water resources of Jiangsu, Shanghai,Zhejiang, Fujian, and Anhui in the District of the Taihu Lake Basin are shown in Table 4.

Fig.1.Comparison of total water use of city-level administrative divisions in District of Taihu Lake Basin in 2015.

Fig.2.Groundwater exploitation of city-level administrative divisions in District of Taihu Lake Basin in 2015.

3.4.2.Prefecture-level WRCC evaluation

(1)Evaluation of carrying status of total water use

It can be seen from the analysis of the carrying status of total water use that the District of the Taihu Lake Basin was generally non-overloaded.Zhenjiang was in a severely overloaded status; Sanming, Ningde, and Xuancheng were in overloaded status; and Nanjing, Quanzhou, Zhangzhou,Nanping,Longyan,and Huangshan were in nearly overloaded status.The remaining prefecture-level cities were in nonoverloaded status.The total water use in the Taihu Lake Basin was generally non-overloaded.All prefecture-level cities were in non-overloaded status, except Zhenjiang, which was in a severely overloaded status.The total water use in the Southeastern River Basin was also generally non-overloaded,except that Sanming, Nanping, Ningde, Xuancheng, and Huangshan were in overloaded status and Hangzhou, Jinhua,Quanzhou, Zhangzhou, and Longyan were in nearly overloaded status.

(2)Evaluation of carrying status of exploited groundwater

It can be seen from the analysis of the carrying status of groundwater resources that the District of the Taihu Lake Basin was generally severely overloaded.Deep confined water exploitation was found in Shanghai, Hangzhou,Ningbo, Jiaxing, and Jinhua with amounts of 4.3 million m3,0.11 million m3, 0.29 million m3, 0.12 million m3, and 4.57 million m3, respectively.According to the WRCC evaluation criteria in the Technical Outline, regions with deep confined water exploitation are regarded as severely overloaded.Therefore,Shanghai,Hangzhou,Ningbo,Jiaxing,and Jinhua were severely overloaded, whereas the other prefecture-level cities were non-overloaded.The groundwater carrying status of the Taihu Lake Basin was generally severely overloaded.There were small amounts of deep confined water exploited in Shanghai, Hangzhou, and Jiaxing, amounting to 1.17 million m3, 0.02 million m3, and 0.12 million m3, respectively.According to the WRCC evaluation criteria in the Technical Outline, these three cities were severely overloaded, and the other prefecture-level cities were nonoverloaded.The groundwater carrying status of the Southeastern River Basin was generally severely overloaded.Hangzhou, Ningbo, and Jinhua had deep confined water exploitations amounting to 0.09 million m3, 0.29 million m3,and 4.57 million m3, respectively.These three cities were severely overloaded, and the other prefecture-level cities were non-overloaded.

(3)Comprehensive evaluation results

The comprehensive evaluation results showed that the District of the Taihu Lake Basin was generally in an overloaded status.Specifically, Zhenjiang, Shanghai, Hangzhou,Ningbo, Jiaxing, and Jinhua were in severely overloaded status; Sanming, Ningde, and Xuancheng were in overloaded status; Nanjing, Quanzhou, Zhangzhou, Nanping, Longyan,and Huangshan were in nearly overloaded status; and the remaining prefecture-level cities were in non-overloaded status.The Taihu Lake Basin was generally in a severely overloaded status due to the severely overloaded status of Zhenjiang, Shanghai, Hangzhou, and Jiaxing, and overloaded status of Xuancheng, even though Nanjing was in nearly overloaded status, and Wuxi, Changzhou, Suzhou, and Huzhou were in non-overloaded status.The Southeastern River Basin was also in a severely overloaded status; Hangzhou,Ningbo, and Jinhua were in severely overloaded status;Sanming, Ningde, Xuancheng, and Huangshan were in overloaded status; Quanzhou, Zhangzhou, Longyan, and Nanpingwere in nearly overloaded status; and the remaining prefecture-level cities were in non-overloaded status.A comparative analysis of the results of the two evaluation methods showed that the reduction index method assigned higher weights to the amount of production water, domestic water, and exploited and used groundwater, and thus its average results were basically consistent with the evaluation results of the binary index method (Technical Outline-based evaluation method).The total water use and comprehensive carrying status of groundwater in the prefecture-level cities in the Southeastern River Basin are shown in Fig.3.

Table 4 Statistical analysis of degree of water resources development and utilization in District of Taihu Lake Basin in 2015.

3.5.Analysis of water resources overloading causes

3.5.1.Effects of severe water pollution on water shortage

With the acceleration of urbanization and industrialization processes in the Taihu Lake Basin,the discharge of sewage has increased sharply, resulting in widespread pollution of river basins and eutrophication of lakes.Water shortage due to poor water quality remains one of the most prominent phenomena in the basin.The water environment is terrible and seriously threatens the safety of urban centralized water supply sources.Due to the rapid economic development of the Taihu Lake Basin, the water pollution control and water resources protection practice lags to a certain extent,leading to severe water pollution in the basin.80% of the river network in the Taihu Lake Basin is polluted,and 70%of the surface water of Taihu Lake is in a eutrophic state.

The water quality in the Southeastern River Basin is generally good.The spatial distribution of water quality has the following characteristics:the water quality of reservoirs is better than that of rivers, the water quality in upstream areas is better than that in downstream areas, and mountainous areas have better water quality than plain areas.The water pollution of rivers in some coastal cities and their surrounding regions tends to be serious.With the rapid development of the economy and society, the pollution load is concentrated in economically developed coastal areas and densely populated urban areas.The low rate of centralized urban sewage treatment leads to a lack of local water resources that meet the water quality requirements in some areas, which seriously threatens the water environment and water supply safety.

3.5.2.Lack of water resources regulation and control causes seasonal shortages

The total amount of water used by the local river network in the Taihu Lake Basin in certain years is far greater than that of the local surface water resources in the corresponding years.The basin mainly relies on water diversion from the Yangtze River and reuse of upstream and downstream water to make up for the shortage of local water resources.After years of water regulation, especially after the implementation of the Taihu Lake water resources regulation project, the water resources regulation and control capability of the basin has improved.However,the overall river water diversion and water resources regulation capabilities are still low, and there are serious seasonal water shortages in the basin.

The Southeastern River Basin has a humid climate and abundant water resources.However, water resources are unevenly distributed in different regions,and some coastal cities and islands are in short supply of water resources.More than 90% of the whole area is hilly.There are many small and medium-sized rivers in this basin, all of which flow into the sea separately.Due to the steep and swift flow in the mountainous upper reaches of most rivers, dense population in the middle and lower reaches, and influence of tides at the estuaries, this basin has a relatively low-level development and utilization rate of water resources and great potential for development and utilization.However, due to the large number of small and medium-sized rivers, short and swift river courses, and influence of typhoons, storms, and tides at the estuaries, it is difficult to develop and utilize the water resources in this basin.

Fig.3.WRCC evaluation results for city-level administrative divisions in District of Taihu Lake Basin (1-Zhenjiang, 2-Nanjing,3-Changzhou, 4-Wuxi, 5-Suzhou, 6-Shanghai, 7-Xuancheng, 8-Huzhou, 9-Jiaxing, 10-Huangshan, 11-Hangzhou, 12-Shaoxing,13-Zhoushan, 14-Quzhou, 15-Jinhua, 16-Ningbo, 17-Lishui, 18-Taizhou, 19-Nanping, 20-Wenzhou, 21-Ningde, 22-Sanming,23-Fuzhou, 24-Longyan, 25-Quanzhou, 26-Putian, 27-Xiamen, 28-Zhangzhou).

3.5.3.Mismatch between socio-economic development and water resources distribution

The Southeastern River Basin is located in the Yangtze River Delta and the economic zone on the west side of the Taiwan Straits.Since the Chinese economic reform, the economy has developed rapidly, infrastructure and investment environments have continuously improved,regional economic vitality has continuously increased, and scientific and technological strengths have been continuously enhanced,making this basin a region with more developed economies, denser industries, and faster development.Although water resources in this basin are relatively abundant,their spatial distribution is uneven, and the layout of social and economic development does not match the distribution of water resources.The upper and middle reaches of the water system are sparsely populated but have abundant water resources,whereas the lower reaches are densely populated and economically developed but have few water resources.The islands in this basin are rich in marine resources and account for 65.8%of all islands in China(except the islands of Hong Kong, Macao, and Taiwan),making this basin one of the regions with the greatest economic development potential.However, due to the special geographical location of the islands, natural freshwater resources are lacking and production and domestic water are in severe shortage, leaving the safety of the water supply uncertain.

3.5.4.Improvement of water resources allocation and utilization efficiency

The use of water resources in the basin is characterized by the problems of extensive management and low water use efficiency.There is still a large gap in water use efficiency between the basin and those in developed countries.Inadequate engineering support for farmland irrigation and extensive irrigation patterns in the basin have resulted in wasted water resources and a large amount of non-point source pollution.Although the level of industrial production technology in the basin is relatively high,the water-saving level still needs to be further improved.The water use efficiency of the Southeastern River Basin is generally low.The current industrial water reuse rate is only 52%,and the average GDP output per cubic water only reaches 40%of developed countries’average level.Therefore,the efficient use, saving, and potential tapping of water resources represent the inevitable trend of water resources development and utilization in this basin.

In the Taihu Lake Basin, water resources are not rationally allocated by quality and quantity, and there is no practical measure for the quality-and quantity-based water supply.After the exploitation of high-quality deep groundwater throughout the basin,a considerable amount is used for industrial cooling,and high-quality water in the mountainous reservoirs in the upper reaches of the basin is mainly used for agricultural irrigation, an improper use of high-quality water.The failure in implementing policies and measures related to proper use of high-quality water and quality-based water supply not only increases the cost of water,but also increases the tension between supply and demand of water resources in some local areas and industries beyond a manageable threshold.

3.5.5.Lack of public awareness and management systems for water resources

Democratic consultation and public participation systems for water management of the District of the Taihu Lake Basin have not been effectively developed, and public awareness and participation areweak.Negotiation,announcement,and hearing systems for water resources management,as well as a water user participation system urgently need to be established.

The water systems in the Southeastern River Basin mostly flow into the sea separately, and basin management mainly relies on provincial government management.All levels of the government still lack a water resources scheduling and allocation system that meets the requirements of the Water Law of the People's Republic of China and other relevant laws and regulations.Therefore, controllable projects and basin-wide water supply channels fail to be uniformly scheduled according to the annual water allocation and scheduling plans.The provinces across the basin see different progress in further revising and improving the provincial water use quota, expanding the measurement scope of water use, and establishing a sound water management system,which combines total amount control and quota management.Therefore, it is difficult to uniformly and effectively implement relevant measures such as total amount control and quota management for a stringent water resources management system.

4.Conclusions

(1)The key point of basin-wide or regional WRCC evaluation is to calculate economic and societal WRCLs, evaluate water resources carrying status, and analyze the causes of water resources overloading.The evaluation must be based on a summary analysis of basic accounts of basin water resources.Therefore,it is necessary to collect and sort out basic data and examine their integrity, consistency, normativity, and rationality for WRCC evaluation.

(2)At present, there are many evaluation indices and evaluation methods for basin-wide or regional WRCC evaluation, and their characteristics and applicability vary.The binary index evaluation method used in this study employed two indices:the total water use and amount of exploited groundwater.This method was characterized by stronger operability and is recommended by the Technical Outline.The reduction index evaluation method was developed through simplifying and optimizing the comprehensive index system to make it more systematic and completed through a combination of the vector model, sensitivity analysis, and dynamic cluster analysis.This method was characterized by simple and targeted indices.

(3)The case study showed that the two methods had distinct characteristics.The combination of the two methods in the WRCC evaluation for the basin enabled their respective results to be mutually verified and adjusted to produce more objective evaluation results.Their combination can provide a useful reference for the WRCC evaluation and analysis of similar basins.