Identification of regional water security issues in China, using a novel water security comprehensive evaluation model

In order to solve regional water security issues, such as shortage of water resources, the aggravation of water pollution, the destruction of the ecological environment, etc., this study proposed the flood control security index, resource security index and ecological security index, respectively, according to the construction principle of human development index. Based on the above security indexes, a novel water security comprehensive evaluation model is established by combining the coupling coordination degree model and the state space model. The proposed model has the advantage of simple operation and fast data speed, which is convenient for water security evaluation in different periods and regions. Taking China as an example, the water security conditions were evaluated from 2007 to 2016 for 31 provincial-level administrative regions in China, including flood control security index, resource security index, ecological security index and water security level of each region, and the specific problems of water security in each region were obtained. The evaluation results are consistent with the actual situation in each region, which provides the scientific basis for the local government authorities to formulate the corresponding regional water security policy. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/). doi: 10.2166/nh.2020.014 ://iwaponline.com/hr/article-pdf/doi/10.2166/nh.2020.014/689031/nh2020014.pdf Jiping Yao Guoqiang Wang (corresponding author) Baolin Xue Beijing Key Laboratory of Urban Hydrological Cycle and Sponge City Technology, College of Water Sciences, Beijing Normal University, Beijing 100875, China E-mail: wanggq@bnu.edu.cn Gang Xie Yanbo Peng Shandong Academy for Environmental Planning, Jinan 250000, China


INTRODUCTION
Water is essential for maintaining the balance of life and the living environment. It is a basic natural resource and strategic resource to promote human economic development and social progress (Masseroni et al. ; Wang et al. b; Yao et al. a, b). Water security refers to the capacity of water resources with quantity and quality guarantee required for human survival and development, Report that the contradiction between supply and demand of water resources in human society is more prominent, coupled with climate degradation and rapid population growth, which leads to more serious water security problems (Russo et al. ; Jiang ; Kumar ; Li et al. ; Fang et al. b). Therefore, it is necessary to study water security and propose solutions to related issues from different perspectives.
Many scholars study water security and related issues from different perspectives. Harris & Kennedy () pointed out that urban water supply should be integrated into the actual urban development planning from the perspective of water supply, and further explored the evolution of urban water security. Rijsberman & van de Ven () revealed the development of urban water security from a new perspective of water resources carrying capacity.

Sullivan () proposed a water poverty index similar to the
Consumer Price Index to reflect the impact of water shortage on human beings. Falkenmark & Lundqvist () paid attention to the water quantity problem, comprehensively considering the shortage of natural water resources and water quality shortage caused by water pollution, and provided a more objective and real basis for local relevant departments to formulate water security protection policies. Ou et al. () used the established entropy weight-fuzzy matter element model to evaluate the rural water safety situation, which effectively reduced the influence of uncertainty and fuzziness in the evaluation process on the authenticity of water safety. Tian & Gang () used the pressure state response conceptual model to evaluate regional water security from the perspective of ecological security.  (Awan et al. ). However, at present, the water security evaluation is only based on the characteristics of the research area or the focus of the research problem, and puts forward the methods to solve the water security problem from different angles. The theory and methods of water security evaluation are not comprehensive enough, and the universality of the proposed evaluation method is relatively low.
In the 1990 Human Development Report, the United Nations proposed the Human Development Index (HDI), which comprehensively reflects the level of human development among different countries and regions by using three variables: human life index, education level index and GDP index (Kawada et al. ). The index plays an important role in guiding the development strategies of developing countries. Therefore, this paper puts forward a flood control security index, resource security index and ecological security index similar to HDI from flood control, resources and ecology, and establishes an evaluation model that can comprehensively reflect the regional water security situation.
The water security of the 31 provinces of China is analyzed and evaluated by the proposed water security evaluation model, and the distributions of flood control security index, the resource security index and the ecological security index are respectively obtained. Additionally, the distributions of water security index which can comprehensively reflect the water security status of each region are obtained. All of the above indexes provide a scientific and reliable basis for a comprehensive understanding of water security problems in various regions of China and for the formulation of targeted strategies to solve water security problems.

Study area and data
According to the three key factors of water security, namely flood control security, resource security and ecological security, the current situation and changes of water security in China from 2007 to 2016 are comprehensively evaluated.
In this paper, 31 administrative regions in mainland China are taken as the research units of regional water security to study the temporal and spatial evolution of water security in China (Figure 1

Methods
Determination of security indexes of the regional water security evaluation model Based on the three key factors of flood control safety, resource security and ecological security, which can comprehensively reflect the regional water security, this paper establishes the flood control security index, resource security index and ecological security index respectively. The three indexes are used to establish the water security evaluation model. The specific calculation methods are discussed below.
The key points of flood control security are casualties caused by flood, economic loss of water conservancy facilities and disaster area loss caused by flood in the region. Therefore, the flood control security index (FS) established includes three data sets: loss rate of disaster area R a , regional flood disaster population rate R c and the ratio of economic loss of water-saving facilities to direct economic loss R e , which reflects the regional social development water. The specific calculation formula is as follows: where R ad denotes flood damage areas (km 2 ), R as denotes flood disaster areas (km 2 ), R cf denotes the number of flood-affected population (10,000 people), R cp denotes the number of population affected by disasters (10,000 people), R ew denotes economic loss of water-saving facilities in floods (100,000,000 yuan), R ed denotes direct economic losses in floods (100,000,000 yuan). Since floods are driven by disasters caused by natural and human events, the five-year moving average value is calculated based on the above data to reduce the impact of the annual flood control security index. The regional flood control security index (FS) is defined as: The resource security index (RS) reflects the coordination between the per capita water resources, urban and rural development level and water supply capacity. The index shows the relative guarantee strength among regional basic resources, economic development level and water supply capacity. The resource security index (RS) includes per capita water resources, urbanization rate and per capita water demand, and its calculation formula is as follows: where W denotes the normalized water resource factor (see Equation (4)), U denotes the urbanization rate (%), and C is the per capita water storage capacity.
where Wr denotes the per capita water resources volume, W is the global per capita water resources volume (6,123 m 3 ), and Wr min is the lower limit of global per capita water resources volume. The per capita water resources of Israel (a country with a serious water shortage), 97 m 3 , is taken as the lower limit of per capita water resources in this study (Liu et al. b).
The ecological security index (ES) focuses on the environmental conditions related to water, which reflects the security of water ecology through the ecological conditions of rivers, lakes and reservoirs. The index includes the ratio of the length of a river above Class III to total river length (RW) and the ratio between the number of non-eutrophication lakes to the total number of lakes (RE). The calculation formula for the ecological security index (ES) is as follows:

Construction of regional water security model
Based on the flood control security index, resource security index and ecological security index, the water security index is proposed to reflect regional water security. Due to the complementary relationship among flood control, resources and ecology (Wilkinson & Bathurst ), this paper introduces the coupling coordination model (Cheng et al. ) to characterize the interaction between flood control, resources and ecology, and the specific calculation formula is as follows: where D FS↔RS , D RS↔ES and D FS↔ES respectively represent the coupling coordination degree of the interaction between the flood control security and the resource security, the coupling coordination degree of the interaction between the resource security and the ecological security, and the coupling coordination degree of the flood control security and the ecological security interaction. a, b and c are the undetermined coefficients of the flood control security index, resource security index and ecological security index respectively, the value of which should be a ¼ On the basis of the above-mentioned security interactions, the state space model (Li et al. ) is used to obtain a water security index (WSI) that can comprehensively consider the impact of flood control security, resource security and ecological security interaction on water security. Based on the above steps, a water security evaluation model is established. The specific calculation formula is as follows: In order to scientifically and effectively show the advantages and disadvantages of water security in various regions, this paper classifies water security into five levels: unsafe, relatively unsafe, general security, relative security and security according to the water security classification standard (Ren et al. ) (see Table 1). Characteristics of flood control security in the study area Table 2 shows the average value of flood control security index (FS) of each administrative region in the study area   Figure 2). The flood control security index for Heilongjiang, Shanghai, Jiangsu, Zhejiang, Henan and Shandong exceeds 0.6, which indicates that the flood control security level of these areas is higher. This is mainly due to the fact that these areas are prone to more rainfall and flood events, are more developed in society and economy, have more investment in infrastructure, and are more advanced in technology, so they have better performance in this regard (Liu et al. b). On the contrary, the flood control security index of other provincial administrative areas is lower than 0.6, which indicates that the flood control security level in these areas is lower. In particular, the flood control security level of Xinjiang and Qinghai in the west of the study area is the lowest at 0.4088. This low level is due to the rare rainfall,

Characteristics of resources security in the study area
Resource security reflects the coordination of regional basic resources, economic development and water supply capacity. Table 3 shows the average value of the resource security index (RS) for each administrative region in the study area from 2007 to 2016, which was obtained from resource security evaluation factors (W, U, C). Based on Table 3, the spatial distribution of the annual average resource security index in the study area from 2007 to 2016 was obtained (Figure 3). In all administrative regions of the study area, the resource security index (RS) of Tibet is equal to 1, which indicates that the level of resource security in the region is very high. This is mainly due to the

Characteristics of ecological security in the study area
Ecological security fully reflects the water quality and ecological characteristics of rivers, lakes and reservoirs.  However, the ecological security index related to water quality of rivers, lakes and reservoirs in Tianjin and Shanxi is lower than 0.2. This indicates that the ecological security of Tianjin and Shanxi is at a low level, which may be Characteristics of water security in the study area Table 5 shows the average value of the water security index (WSI) for each administrative region in the study area from 2007 to 2016, which was obtained from FS, RS and ES.
Based on Table 5, the spatial distribution of the annual average water security index in the study area from 2007 to 2016

CONCLUSIONS
Based on flood control security, resource security and ecological security, which can comprehensively reflect the water  and Ningxia is relatively low, so it is urgent to strengthen the restoration and protection of ecological water environment in these areas. Compared with the traditional water security evaluation system, which needs multi-layer design, a complex calculation method and different evaluation indexes, the water safety evaluation model proposed in this paper has clear theory, simple structure, easy interpretation, strong robustness, and good promotion and application.