Policy effectiveness of water conflict management: A textual analysis of the Nansi Lake Open Access

Water resource is an essential field of economic growth, social progress, and environmental integrity. Rapid population growth and industrialization have contributed to a dramatic decline in the supply of freshwater. As a result, desalination is an important choice to solve the global problem of water scarcity (Panagopoulos, 2021a). On the one hand, water is valuable for potable water (via desalination). On the other hand, the brine from seawater desalination plants recovers not only freshwater, but also solid salts with commercial value by utilizing zero liquid discharge (ZLD) systems (Panagopoulos, 2021b). Whether only freshwater is sold or both freshwater and mixed solid salt are sold, both scenarios are profitable (Panagopoulos, 2021c). In addition, control over water resources has traditionally been associated with state control and domination by national rulers (East & Wittfogel, 1960; Worster, 1983). Water scarcity often emerges as a political strategy to struggle over access to and control over resources (Mehta, 2013). Therefore, water scarcity is composed of water insufficiency and water mismanagement (Hussein, 2018).

The crisis of water resources is getting worse, which leads directly to the frequent occurrence of water conflicts in international rivers and lakes. Water conflicts have gradually become one of the most disruptive factors in the global political landscape. The hydro–politics relationship has become one of the most complex geo-relationships that countries and the international community urgently need to face and handle (Lu et al., 2020). In fact, shared interests along a waterway seem to overwhelm water's conflict-inducing characteristics. By its very nature, water is a resource whose characteristics tend to induce cooperation even as disputes rage over other issues, and the transboundary cooperation as a development issue which needs positive efforts at an international level to support should remain in that space (Wolf, 1999a, 1999b; Cascão et al., 2018). Promoting water cooperation in its various forms has become a moral imperative and a recognized political need of our era (Salamé, et al., 2021).

Nansi Lake is located on the border of Shandong Province and Jiangsu Province in China. It is composed of the Nanyang Lake, Zhaoyang Lake, Dushan Lake, and Weishan Lake. It is the largest group of freshwater lakes in the Shandong Province. Due to many factors, the Nansi Lake has been a series of complex water conflicts since the Ming and Qing Dynasties. According to incomplete statistics, there have been 53 conflicts in the Nansi Lake, resulting in nearly 70 deaths, more than 1000 injured (to different degrees, among which more than 100 were seriously injured), including three cases of being permanently incapacitated, two missing, in addition to more than RMB 8 million in property losses, more than RMB 10 million in lost fish and shrimp, on top of these the disappearance of 533,600 ha of shoaly land, more than 40 houses, more than 50 boats, and more than 1000 production tools and daily necessities. One of the issues that people are most concerned about is how to use policies in rational and effective manners when dealing with water conflicts and to maintain the stable development of society.

In view of the long history and severity of the water-related conflicts in this region, this paper will use the method of textual analysis to classify water conflict events based on the perspective of bibliometrics and take the Nansi Lake as an example in its discussion of various types of policy measures that have been adopted revolving around different focal points and the circumstances in which some specific measures play their part in the resolution of the crisis. Based on the textual analysis, the external and hidden nature of the policy are revealed by the extraction of the most important semantic component, the induction of content summary, and text classification (Graneheim & Lundman, 2004). These give the quantitative laws and political phenomena. It is conducive to grasp the policy orientation and strategic trend so that corresponding predictions and suggestions on the policy of water conflict management are made. Hopefully, the paper will shed some light on the effectiveness of the policy measures.

In recent years, public conflict resolution has emerged as a new research perspective. The resolution of public conflicts can make up for the existing deficiency of public governance mechanisms. It is conducive to the rational use of public and government resources, and is closely related with social stability. At present, there is no consensus or accepted definition of ‘public conflict’ in the academic circles. It is generally believed that public conflicts include not only conflicts that are included in public management, policy formulation and implementation, but also those involving public affairs, public or collective resources, as well as those whose development may affect public interests, although they are not triggered by public matters, such as social order and stability (Li, 2012; Li & Li, 2015).

In the 1960s, the public choice theory, a new branch of economics, came into being in the study of non-market decision-making issues, that is, collective action issues. Olson (2009) pointed out that due to the non-exclusive and non-competitive nature of public goods, if each individual makes a rational choice, then individual rationality will lead to collective irrationality and micro-motives with the best individual utility result in a lack of cooperation at the macro level in his book The Logic of Collective Action. This phenomenon is called ‘a dilemma of collective action’. Olson found that important factors affecting the difficulty of cooperation include two aspects: the number and homogeneity of actors, in addition, he designed a dynamic mechanism for the group to achieve common interests – selective excitation.

The American scholar Hardin (1968) published an article ‘The Tragedy of the Commons’, in which he drew attention to a land system that once existed in the United Kingdom. Under this system, the feudal lords set aside a part of the land as a pasture and opened it to herders free of charge. As a result, every herdsman raised cattle or sheep, as many as possible. With the unrestricted increase in the number of animals, the public pastures would eventually degenerate due to overgrazing. A large number of herdsmen's cattle and sheep starve to death and public pastures are prone to desertification. Similarly public forests are prone to deforestation, and public fishing grounds, overfished. He calls this phenomenon ‘the tragedy of the commons’.

A common form of public conflict is land conflict. Nantel et al. (1998) described land conflict as a manifestation of the underlying social contradictions, which are related with land use patterns under specific circumstances. After studying the contradictions in Kenyan herding, farming, and wildlife protection, Campbell et al. (2000) explained that land conflict is ongoing competition over access to scarce land and water resources between various land use methods. According to Tan (2008), the land conflicts in China are land-related excessive behaviors actualized by individuals or organizations. Some scholars tend to focus on the factors leading to land conflicts and the mitigating measures. They propose to find a balance of interests between government and farmers by establishing a sound legal system and social security system, which will provide a compulsory mechanism to solve public conflicts through spontaneous cooperation and collective action (Dixit & Olson, 2000). Other researchers believe that the main causes of land conflicts are the change of land systems, ill-defined property rights, the unbalanced social and economic development, and the pursuit of self-interests at others’ expenses (Wehrmann, 2008).

Hui & Bao (2013) established three innovative models in relation to the dynamic model for conflicts of legal land acquisition, the game model of illegal land acquisition, and the game model of the black land market. Based on the perspective of the hypothesis of ‘rational man’, they explain how disputes and conflicts evolve and illustrate the logic and strategy of conflicts between local governments and farmers. Baranyi & Weitzner (2006) regarded the settlement of land conflicts as a process of management, avoidance, transformation, and resolution, and in this process, he proposed that transformation is the most important, because transformation will make possible land appropriation-related conflicts develop in a favorable direction. Urresta & Nixon (2004) considered problems from the perspective of judicial administration and analyzed the significance of judicial guarantees for resolving land appropriation-related conflicts. He and his team also experimented land dispute forum by combining both civil and legal coordination mechanisms for the resolution of land appropriation-related conflicts.

Nobel laureate in economics, Coase (2013) is regarded as the founder of property rights theory. He proposed that the most direct and effective way to solve the short supply of public goods is to have the particular goods privatized. With a well-defined private ownership, consumers are supposed to bear the resulting costs, which will prevent negative externalities and free-riding behavior. However, some scholars believe that privatization is not a panacea. Ostrom (2012) did a comparative analysis of the efficiency of the use of public resources (mainly natural resources) in the case of government, collective and private property rights in the book Why Do We Need to Protect Institutional Diversity, pointing out that it is necessary to design adaptive, multilevel governance systems related to complex, evolving resource systems, and overcome the tendency to recommend panaceas and encourage, instead, considerable experimentation at multiple levels to reduce the threats of massive collapses of valuable resources.

John Burton, known as the ‘father of conflict analysis and resolution philosophy’, firmly believed that needs are one of the origins of international conflicts while prevention and conflict resolution procedures are necessary policies (Frankel, 1986). The problem-oriented conflict resolution regarded conflict resolution as a process, not only to resolve the causes of conflict, but also to create the condition of developing cooperative relationship (Dunn, 2004). Following some qualitative analysis, Mascarenhas & Scarce (2004) suggests that a successful public planning process must have fair representation, appropriate government resources, and be consensus driven – the three components of legitimacy. Therefore, the resolution of public conflicts requires cooperation, that is, the actions of various independent individuals or organizations become aligned through the process of negotiation (policy coordination) (Tömmel, 2007), so as to resolve differences in the interests of all parties, share benefits, and avoid ‘the tragedy of the commons’ caused by rational choice.

Due to the complex public attributes of the Nansi Lake and the semi-public benefit of water, the resolutions procedures of public conflicts have certain significance for the solution of the water conflicts in the Nansi Lake.

International water resources are widely distributed around the world. According to data from the United Nations Water Mechanism in 2019, there are 276 international rivers in the world, and their basins cover nearly half of the earth's land area, on which nearly half of the world's population reside. A total of 145 countries’ territories includes international river basins, of which 21 countries’ territories are all international river basins.

Regarding the management of international water conflicts, most scholars have focused on quantitative research into water politics, exploring meaningful use of data and quantitative methods. For example, researchers carried out a study of the factors which have impacted on water conflicts and the level of water cooperation in the international rivers. In their studies, they tend to regard water conflict or water cooperation as an independent variable. Also, the analysis perspective includes water scarcity, institutional factors, upstream and downstream relations, economic and trade relations, etc. Some scholars focus on the research into water conflicts and water cooperation relations within a few transnational river basins (Dinar et al., 2011, 2015; Munia et al., 2016).

Cross-basin governments and relevant international organizations attach great importance to the management of water resources conflicts in the river basin, and have carried out extensive cooperation in the development and management of water resources in the river basin. The non-governmental organization Green Cross International raised the issue of water conflicts and conflict resolution strategies at the First World Water Forum held in 1997, and set out to establish an arbitration model for resolving water conflicts in different regions of the world. The sub-thematic forums of the Third World Water Forum proposed strengthening the management of international rivers by using water to promote peace, with a view to effecting a transformation from potential conflict to potential cooperation (Beaumont, 1997; Correia & Silva, 1997; Swain, 1997). Based on relevant documents in the fields of conflict management, peace economics, and peace science, Chatterji et al. (2017) offer a study of conflict management of water resources to focus on the management of water conflict and its implications for peace.

Dolatyar & Gray (1999) proposed that the tremendous economic and domestic political risks that are assumed by states in pursuing water development projects warrant full consideration in a study that professes a ‘multidisciplinary’ and ‘holistic’ approach to studying hydro–politics as a transboundary issue. Gizelis & Wooden (2010) found better governance and institutions can ameliorate the consequences of water scarcity and effects of water scarcity on conflict differ between democratic and non-democratic regimes. Chatterji et al. (2017) showed that the problems of the shared aquifers are adequately framed as an environmental inter-generational problem, rather than a problem of allocating a fixed resource between two parties, and was crucial for advancing a joint management concept.

Southeast Asian countries have frequent cooperation on the development and protection of water resources of the Mekong River (Lu et al., 2020). In 1995, the Mekong River Commission was established. The four lower Mekong countries, by replacing ‘political needs’ with ‘economic development needs’ gradually, succeeded in maintaining good relations in the management of Mekong water resources. This has brought into being a political cooperation on sub-regional level, which resulted in four types of cooperative benefits in the international river basins and reflected a wide range of political, geographic, economic and cultural circumstances (Sadoff & Grey, 2002).

In terms of the construction of water rights system, the United States has identified the following related right systems: riparian right system, prior appropriation water rights system, hybrid water rights system (American Water Works Association, 2016). The public trust doctrine (Sax, 1970) is mainly applicable to the field of water resources. Therefore, there is a close relationship between the water right system and the public trust doctrine. If it can be used correctly, it will be of great help to the solution of water right conflicts. China implements a licensing system for water resources concession, from the difference between public trust doctrine and water rights system and the balance of conflicts, to a certain degree, China's water concession rights are essentially regulated and controlled. Therefore, China should make full use of the relationship between the water rights system and the public trust doctrine to deal with water rights conflicts.

In the study of the Indus River and water used between India and Pakistan, it was found that the way to resolve the water conflict between India and Pakistan should include the conclusion of a water-sharing treaty, the establishment of a standing river committee, the establishment of a transition period for water use, the implementation of the Indus River Basin water transfer project, and the participation of international organizations in mediation and arbitration (Giordano et al., 2002).

Canada is relatively advanced in the development, utilization, protection, and management of water resources. Bakker & Cook (2011) argued that fragmented governance has had negative impacts on Canada's ability to manage water resources adequately (particularly in the context of urbanization, agriculture and resource extraction), and to deal with new issues (such as climate change). Furthermore, it argued that Canada's highly decentralized approach to water governance creates challenges of integration, coordination and data availability. They explored possible future strategies for innovations in water governance that may have the potential to improve water management outcomes.

The conflicts of international rivers mainly focus on the development and utilization of river basins and the pollution of the water environment (Jia & Dai, 2003). The theory of water rights can provide an effective way to resolve international water conflicts, help avoid water wars, and maintain regional stability. Similarly, we can also solve the problem of water rights conflicts in the Nansi Lake through the rational use of water rights theory. For example, the definition of pollution rights would raise to the attention of downstream cities not only the amount of pollution in upstream cities, but also the specific types and concentration of the pollutants, urban industrial structure, and the scale and status of production activities, etc.; with development and utilization rights to define, the cities need to pay attention to their approach to and the intensity of the urban development and its impact on regional biodiversity and ecological balance, as well as the rehabilitation capacity, and the measures implemented for the area-wise pollution control and their effects, etc. Downstream cities are disadvantaged when water pollution occurs. Therefore, they tend to impose higher requirements on upstream cities, especially the cities where the source of pollution is located. Given the differences in terms of science and technology levels, of social and economic development, and the social system among cities in one river basin, the impact or effect of the exercise of water rights will also be significantly different, especially in the protection of water resources and water environment. All of these require the guidance of water rights theory. The research on water rights theory and its application still needs to be deepened.

The problem of water rights conflicts in the Nansi Lake has existed for a long time, and it is obviously impossible to resolve simply by using some international experience; but the international experiences in dealing with water conflicts in the upstream and downstream of the basin are valuable to us. They include an emphasis on integrated management and non-engineering alternatives, strengthening of the legislative structure for water resources management, a salient feature in the protection of water resources, application of new technologies, emphasis on the use of water rights systems, public trust doctrine, water rights theory, and the establishment of water-sharing treaty and development strategy for water resources.

From the perspective of the participation of water management agencies and the size of their coercive powers, the resolution of foreign water conflicts can be divided into agreement, negotiation, and coordination (Dore et al., 2010).

Agreements are entered into by representatives of different regions on river management. It was recognized by the early 1990s that there was an urgent need to reform water resource management in the Murray–Darling River system. This has led to culminating in the Murray–Darling Basin Plan over the past 30 years (Hart, 2016). The Council of Australian Governments (COAG) then adopted (2004) the National Water Initiative and this intergovernmental agreement established the National Water Commission (NWC) to reform the water entitlement system. In 2007, the Australian Parliament passed the Water Act (2007), with Basin governments agreeing that the Australian Government take a larger coordinating role in the integrated management of the Basin's water resources. Azerbaijan is party to three agreements with its neighbors on transboundary rivers: with the Islamic Republic of Iran on the Aras River, with Georgia on the Gandar Lake and with the Russian Federation on the Samur River (Ahmadov, 2018). Since the beginning of the 1990s, the problem of delimiting the border between Russia and Azerbaijan has arisen. On 28 August 28, Agreement No. 1416 was signed on the delimitation of the border between the Russian Federation and the Republic of Azerbaijan, as well as on the rational use and protection of water resources of the Samur River (Ahmadov, 2018). In the Senegal River basin, cooperation and benefit sharing took place when the riparian countries found a suitable solution for their political conflicts, followed by a trilateral agreement to achieve collective political and economic benefits (Geneva Water Hub, 2015). The Helmand River treaty is an agreement first discussed on 4 March 1857 between Afghanistan and Iran and concluded in 1973, which was developed based on attempts to resolve existing water disputes between the two riparian states (Goes et al., 2016). Afghanistan and its neighboring countries and changes of watercourses are the responsibility of the Ministry of Energy and Water (MEW), with agreements from the Ministry of Foreign Affairs (MoFA), Ministry of Interior (MoI), and the Ministry of Border and Tribal Affairs (MoBTA) (Water Law, 2009). In 2016, President Ghani declared the establishment of the Transboundary Waters Commission where different relevant ministries are involved in decision-making. Around the development and management of international rivers, 145 relevant water agreements have been signed worldwide in the 20th century (Wolf, 1999a).

Negotiation is necessary for the parties involved to better supervise the implementation of river management agreements and to resolve transboundary water conflicts, if there are any, more flexibly. Some river basins have set up informal consultation organizations to coordinate actions in various regions. The main functions of this kind of organization are coordination, research and advocacy, and its decision-making needs to be agreed by all, and there is almost no coercive power. Bilateral negotiations between Azerbaijan and Georgia on joint management of water resources in the Kura basin. The coordinating committees of the ‘National Dialogue on Water Policy’ receive information on the progress of negotiations and discuss it at their meetings (Ahmadov, 2017). Take the Fraser Basin in Canada as example. Before the emergence of a basin-wide management organization in 1997, the upstream and downstream areas were under decentralized management. After that, a purely consultative organization, the Fraser Basin Committee, was established, based on the consensus of the regions and communities in the basin. Sudan and Egypt in the Nile River Basin have also established a joint committee on the basis of the agreement to jointly negotiate and resolve the wading of the Nile River. In recent years, the establishment of interstate associations to solve interstate water problems has become a significant trend in cross-state watershed management in the United States. For example, in the Missouri River Basin, two informal associations were established to coordinate interstate water affairs. The Great Lakes Committee was established to coordinate water issues in the Great Lakes region (Mandarano et al., 2008). Although present studies on water issues mostly regard countries as singular entities, and focus on the physical features, the outcome of water negotiations is likely to be determined by analyzing internal discourses to understand the positions of the different parties in water negotiations, and the way water issues are framed may have a pivotal role in determining the prospects for successful conclusion of water agreements (Feitelson, 2002). Besides, the explanation to transboundary water governance needs to be contextualized in the broader context, considering national security, regional geopolitics, inter-sectorial interests, and power asymmetries (Hussein, 2019).

Coordination is an integral part since negotiation has no compulsory power. Integrated water resources management (IWRM) is to set up a cooperative management structure that goes beyond the triangle of legislative committees, regulatory agencies, and special interest groups (e.g., industrial and environmental) and takes into account all actors who are directly affected by the deficits and are the potential winners or losers in the process (Hering & Ingold, 2012). Partnership and Cooperation Agreement (PCA) between European Union member countries and Azerbaijan (signed on 22 April 1996 in.Luxemburg) became effective from 22 June 1999, which indicates a high level of cooperation between the two sides. The European Union is implementing the EU Water Initiative ‘UNECE Convention on the Protection and Use of Transboundary Watercourses and International Lakes’ in Eastern Europe, the Caucasus and Central Asia (EECCA) region (The EU Water Framework, 2000). Mozambican water sector has managed to plan and implement a number of reforms to align itself with IWRM concepts following the approval of the National Water Law in 1991. This process meant creating water resources management institutions at river basin level. The Regional Water Administration designate River Basin Management Units (RBMU) for specific river basins within its particular region to devolve powers and hold them responsible for the implementation of IWRM at the grass-root level. Also, it is the responsibility of a RBMU to facilitate and promote civil society participation in the management of water resources affairs through the respective River Basin Committee (Gallego-Ayala & Juízo, 2012). Part of that responsibility also requires proposing and implementing mechanisms for water resources protection and reconciliation in water use conflicts among other issues. The states are responsible for irrigation and flood control in India's watershed governance. The central government is mainly responsible for coordinating interstate relations. Agencies on the national level include National Water Resources Commission, the Central Water Commission and the Ministry of Water Resources and other central institutions, which function to achieve interstate coordination. The governance issues are complex but can also determine the degree of success in implementation (Rauschmayer et al., 2009). Skillful guidance and leadership are particularly needed for effective participatory processes (Reed, 2008), as shown by the greater success of flood control measures involving agricultural land when local leaders facilitated cooperation and information exchange (Ingold et al., 2010). The basin committee in France is equivalent to the ‘water parliament’ within the basin. It is a legislative and advisory body for river basin water conservancy issues and has strong compulsory powers (Sangaré & Larrue, 2002).

In view of the above review, although the existing researches on the water conflict management has been relatively mature, there is a lack of evaluation and analysis on the different types of policy measures adopted, as well as the role played by specific measures in the crisis circumstances. There has not yet been a comprehensive study of transboundary water conflicts management based on policy texts, and most of the researches focus on the operation mechanism of solving water conflicts with a single method. Therefore, this paper uses the method of textual analysis to classify the policy of water conflict management in the Nansi Lake during hundreds of years and conclude the policy effectiveness. This study is significant and valuable because it probes into the differences of policy effect under the different type of transboundary water conflicts and specially analyze the correlation among them. The case of policy of water conflicts management in the Nansi Lake is presented here for the first time as the object of textual analysis. It provides a future direction in water conflict management through analyzing how textual analysis can be used in better policy optimization.

Textual analysis, also referred to as text mining or data mining, is the process of deriving valuable information from text (Guo et al., 2016). It extracts information from a dataset and transforms it into a meaningful structure for further use by parsing text under the actual situation. The process of textual analysis is not fixed, generally including text review, identification and evaluation, classification, and sorting (Babbie, 2020).

At present, textual analysis deals with the objective, systematic and quantitative description of the manifest content of communication and interpretations of latent content (Graneheim & Lundman, 2004). The linguistic knowledge allows us to identify the cognition and expectation of the authors by text content. More precisely, the mechanism of the decision-making process can be explained by mining factors such as cognition as a necessary link. Content analysis underlines the development of categories from the data and recognizes the importance of understanding the meaning of the context where the analyzed items appear. It enables textual analysis to identify, abstract and condense theoretical and practical information from the data and recognizes the profound essence (Hsieh & Shannon, 2005).

Textual analysis is a mainstream form of qualitative and quantitative research in the Social Sciences that provides open spaces for imagining how the social world may be reorganized to address deeply rooted social problems. The true power of textual analysis is in engaging in deep thinking with texts to identify imbalances of power and open up avenues for positive social change (Baxter, 2020). As a matter of fact, the qualitative nature brings difficulties to developing effective policy for public management. Complex issues involving a wide range of social, political, organizational, ethical factors and policy environments need to be considered. Through textual analysis of qualitative research, both intended and unintended information can be extracted on a timely basis (Li, 2020). In that sense, it has the potential to analyze policy effectiveness of water conflict management. In fact, an increasing number of current studies has started to use textual analysis to measure the naturally qualitative elements. Thus, it has strong scientific and rationality to quantify policy texts resolved water conflicts based on textual analysis.

In this study, we first examined the water conflict events in the Nansi Lake since the Ming and Qing Dynasties by using a series of literature regarding the Nansi Lake. Then, we classified the different focal points of water conflicts and policy measures that have been adopted revolving around them on the basis of high frequency topics of water conflict and policy in the Nansi Lake. Also, we explored and gathered statistics that the effects of measures in the resolution of the crisis. With the help of relevant historical records, the water conflicts in the Nansi Lake have been divided into the following seven types: administrative management, lake production, shoaly land, water resources, water conservancy, land, and fishery management. Also, the policy measures have been divided into the following five categories: engineering measures, administrative consultation, administrative law enforcement, civil consultation, and policy regulation. This classification also takes into account the time sequences and geographic locality of water conflict focuses, policy measures, and measures effects to analyze the correlation of them. In order to ensure the neutral attitude of researchers and reduce the subjectivity of research, this paper, based on the descriptive analysis and cross-correlation analysis, tries to conclude the policy effectiveness in the Nansi Lake with the help of textual analysis.

As a lake on a provincial boundary, the Nansi Lake has experienced water conflict since ancient times due to its geographic location. This part systematically summarizes the Nansi Lake water conflict events and presents statistics regarding the relationship, frequency, and centrality of water conflict events, as well as the focal points, measures taken, and the ensuing effects.

In general, conflicts mostly concerned shoaly land and lake production, each of which observed 35 instances of conflicts, each accounting for 28.9%, conflicts involving administrative management happened 25 times, accounting for 20.7%; and there were also many conflicts over water resources, 16 times in total, accounting for 13.2%. There were fewer conflicts in water conservancy and fishery administration, which were recorded four times and five times respectively, accounting for 3.3 and 4.1% of the total conflict cases, respectively. Land conflicts happened only once, accounting for 0.8%. Among the measures taken in response to different conflicts, administrative consultation was used the most, reaching 42 times and accounting for about 34.7% of the total. Engineering measures and policy regulation measures were second in adoption, both being 28 times and each accounting for 23.1%. The administrative law enforcement was taken 16 times, accounting for 13.2%; civil consultations were the least adopted measure, which was used seven times and accounted for 5.8%.

In general, among the 115 measures implemented, the frequencies of successes were 79, accounting for nearly 70%, 12 partial successes and 24 failures and the proportion of failure was approximately 20%. Among them, the success rate of administrative law enforcement was the highest, reaching 85.7%, followed by the success rate of administrative consultation, reaching 82.9%, the success rate of policy regulation is a little lower at 74.1%, and the failure rate of engineering measures was the highest reaching 55.6%.

The water conflicts of the Nansi Lake spanned 200 years, and the areas where conflicts frequently occurred and the focus of conflicts have continued to change over time. The Nansi Lake is affected by its unique geographical location and historical problems so that the focal points of the conflict and the resolution measures taken by the local government to address conflicts have shown diversity, and the effects of specific measures have also been different. Therefore, this part shed lights on the Nansi Lake water conflict events in all directions from multi-dimensional cross-correlation statistics and analysis on the focuses of the Nansi Lake conflicts.

In general, five measures have been effective against administrative management conflicts. Among them, the adoption rate of administrative consultation is higher, accounting for 40%, and the number of times of civil consultation and policy regulation is fewer, but it can be successful every time. In view of conflicts in lake production, administrative consultation and policy regulation are used at a high rate, and the success rate is also high. Although the engineering measures are used at a high rate, the effect is not significant and the failure rate is high. The effects of the three times civil consultation are all partial successes, which indicates that further improvements are needed or they need to be combined with other measures. All four administrative law enforcements have been successful, and the chart indicates that the use of administrative law enforcement to solve such problems is more effective. In view of the conflict over shoaly land, the adoption rate of engineering measures and administrative consultation is high, but the failure rate is not low, while the low utilization rate of administrative law enforcement and civil consultation have a high success rate, and the utilization rate of policy is also relatively high, but there is defect that this kind of measure has a high partial success rate. Regarding the conflict of water resources, although only three measures have been adopted – engineering measures, administrative consultation, and policy regulation, they have all been successful. Whether the other measures are equally effective requires further consideration. In response to conflicts in water conservancy, only engineering measures have been taken. The frequency of use is not much, but the success rate is high. It remains to be investigated whether other measures can be considered in the future. Regarding land conflicts, only administrative law enforcement is taken once, but it failed. There are few data so more work needs to be done. In addressing the conflicts in fishery administration, only three types of measures were used, namely, administrative consultation, administrative law enforcement, and policy regulation. Also, they were used less frequently but they all achieved successes. In the future, we can consider integrating other measures on the basis of these three measures.

From the figure it can be seen that the frequency of conflicts surrounding shoaly land and lake production is the highest among all types of conflict. The engineering measures, administrative consultation, and policy regulation are highly involved in the network of water conflict incidents. Civil consultation as one of the policy measures has the lowest participation in the network of water conflict incidents:

• In the relationship network with administrative consultation as the node, the lines connected to the administrative consultation with lake production (success), water resources (success), and administrative management (success) are relatively thick, that is, the node and lake production (success), water resources (success), and administrative management (success) are the most closely linked, which indicates that administrative consultation has greater impact on conflicts focusing on lake production and water resources, and has achieved better results. The effectiveness is high.

• In the relationship network with administrative law enforcement as the node, the lines connected to administrative law enforcement with lake production (success) and shoaly land (success) are thick, that is, the node and lake production (success) and shoaly land (success) are the most closely related, indicating that such measures of administrative law enforcement have a greater impact on the types of conflicts focusing on lake production and shoaly land, and have achieved better results and higher policy effectiveness.

• In the relationship network with policy regulation as the node, the line connected to policy regulation and lake production (success) is the thickest, that is, the node has the closest connection with lake production (success), indicating that the policy regulation has greater influence on the type of conflict focusing on lake production, and it has achieved better results. The policy effectiveness is high.

• In the network of relations with engineering measures as the node, the line which is connected between engineering measures and lake production (failure) is the thickest, that is, the node is most closely related to the lake production (failure), indicating that engineering measures are mostly used to resolve conflicts that focus on lake production, but the effect is poor and the effectiveness is low.

• In the relationship network with civil consultation as the node, the line connected to the civil consultation and the lake production (partial success) is the thickest, that is, the node has the most closely connection with the lake production (partial success). It indicates that civil consultation is mostly used to resolve conflicts in lake production, but the result is average, and the effectiveness of the policy is relatively average.

In general, administrative consultation as one of the policy measures is mostly used to resolve water conflicts focusing on lake production, water resources, and administrative management, and the policy effectiveness is generally better. The policy effectiveness of administrative law enforcement which is mostly used to resolve water conflict incidents focusing on lake production and shoaly land is generally better. The policy effectiveness of policy regulation which is used to resolve water conflict incidents focusing on lake production is generally better. Also, the engineering measures are mostly used to resolve water conflict incidents focusing on lake production, but the policy effectiveness is generally poor. The civil consultation as one of this type of policy measures is mostly used to resolve water conflict incidents focusing on lake production. Also, the effect is relatively ordinary. The following conclusions are drawn from this:

• Policy measures, including administrative consultation, administrative law enforcement, and policy regulation can all be used to resolve water conflicts that focus on lake production. It is predicted that these policy measures will achieve better results, while engineering measures are not applicable to lake production. In the water conflict incidents focusing on lake production, the use of engineering measures should be reduced. Since civil consultation has a relatively common effect in water conflict incidents that focus on lake production, they can be used in combination with other types of measures.

• Administrative consultation can be used to resolve water conflict incidents focusing on water resources and administrative management, and this type of policy measure will be expected to achieve better results.

• Administrative law enforcement can be used to resolve water conflict incidents focusing on shoaly land, and this type of policy measure will be predicted to achieve higher policy effectiveness.

We divide the occurrence of conflict events into three stages according to time. The first period is from 1805 to 1953, the second period is from 1953 to 1980, and the third period is from 1980 to 2006. What happened at time nodes to divide three periods are: (1) the establishment of Weishan County and the implementation of the specific delimitation agreement in 1953; (2) The implementation of the 1980's Water Division Agreement. The reasons for taking these as our landmark events in different periods are: (1) these events are both measures of profound historical significance for the government to resolve the conflict in the Nansi Lake; (2) The implementation of these events has certain drawbacks and has caused obvious changes in the relevant attributes of water conflicts in the Nansi Lake.

According to statistics, the relevant data and characteristics of the first period (1805–1953) are as follows: in this period, water conflicts occurred 12 times in total. We divide the first concentrated period of conflicts into three stages according to the ruling periods of the emperors and calendar year, respectively the reign of the Emperor Jiaqing, the reign of the Emperor Xianfeng and Tongzhi, and from the reign of the Emperor Guangxu to 1915. The intensity of the conflict is evaluated based on the number of conflicts occurred in these stages and expressed by the number of stars (from 1 to 3 indicates from weak to strong). According to statistics, conflicts occurred most frequently during the reign of the Emperor Xianfeng and Tongzhi. There were six conflicts during the reign of the Emperor Xianfeng, accounting for one-half of the total conflicts in the first period, and the conflict intensity was rated three stars; there were three conflicts during the reign of the Emperor Tongzhi period, accounting for one-quarter of the total conflicts in the first period and the rating of conflict intensity is two stars. As the Yellow River burst its dykes, floods followed and refugees drifted away, each acting on their own, combined with the government's forceful suppression, trenching and dike building and other procrastinating measures to stop the imminent danger, the conflicts focused on water conservancy and administrative law enforcement in this period (Zhang, 2016). A total of nine conflicts incidents occurred surrounding the two types of focal points, accounting for three-quarters of the total conflicts during this period. The two parties involved in the conflict are mainly the lake regiments which is a kind of the self-defense and autonomous village militia organization established by the refugees who reclaimed the shoaly land from Caozhou and Jining in Shandong Province and the counties on the coast of Weishan Lake in Jiangsu Province and the Shandong Province such as Pei County and Feng County in this stage (Bao, 2020). Among them, the two parties with the most intense conflicts were Pei County and Xin Regiment. There were four major conflicts that occurred between them, which caused serious casualties on both sides and led to murder cases. It is one of the roots of future conflicts in the Nansi Lake.

In the second period (1953–1980), the establishment of Weishan County on 22 August 1953 was a landmark event. According to the approval of the State Council, ‘It was agreed that Shandong Province set up the villages reliant solely on fishing and the villages partially reliant on fishing along the lake to Weishan County on the basis of the lake regions of Weishan, Zhaoyang, Dushan, and Nanyang.’ The establishment of Weishan County marked the transformation of the jurisdiction system of the Lake District from ‘divide and conquer’ to ‘integration management’ (Tian, 2014). At the same time, according to the agreement signed between Jiangsu province and Shandong province in 1953, the specific boundary of the two provinces was stipulated as ‘basically, shoaly land is the boundary’. The boundaries of shoaly land would continue to change with the rising and falling of the lake, resulting in ambiguous boundaries and obscure property rights after the establishment of Weishan County in 1953. As a result, there have been constant conflicts among stakeholder counties in the region of the Nansi Lake. Conflicts on a huge scale have happened 19 times in total. According to incomplete statistics, 31 people were killed and more than 150 people were injured. Among all conflicts, the ‘Dianzi Incident’ conflict in 1973 was particularly fierce. In this conflict, 30 people died and about 57 were injured. The losses were serious, which attracted the attention of the central government. During this period, the two parties in the conflict were mainly represented by Pei County and Weishan County. The two provinces were eager to defend their own interests so violent conflicts occurred frequently. From 1953 to 1980, the two counties had 14 conflicts, accounting for 14/19 of the total conflicts in the second period. At this time, the focus of conflict was on shoaly land and lake productions, which became the main spotlights of conflict in the second period with a rate of 99.9%. The incidents of grabbing shoaly land and cutting reeds occurred frequently.

In the third period (1980–2006), the landmark event was the signature of the 1980 Water Division Agreement. After 1980 the conflict in the Nansi Lake was serious (represented by Pei County and Weishan County) because the counties challenged the regulations of ‘shoaly land is the boundary’ raised in 1953 and made many petitions to the higher authorities requesting a redefinition of the boundaries of Nansi Lake in the two provinces. After considering the resolution plans of the Nansi Lake's relevant departments and Wei and Pei counties, the central government finally decided that Weishan Lake is the area below the secondary dam. In principle, the central line of the lake represents the boundary of the two counties. The portion to the west of the central line was returned to Pei County, and the east of the central line was returned to Weishan County.

Before 1980, the grievances between the both sides could not be completely resolved. In addition, the 1980 Water Division Agreement still has disadvantages, such as inconvenience for the residents of the two places. Also, the conflict after 1980 is continuing. According to statistics, a total of 11 conflicts occurred in this region from 1980 to 2006. Pei County and Weishan County remain the main conflicting parties, and shoaly land and lake production are the main conflicts. However, the problem of water resources has emerged as a new focal point of dispute during this period. The conflicts focusing on water resources have occurred four times, accounting for 4/11 of the total conflicts in this span time. The reason for this is as stated in the ‘Research and Opinions on Several Issues in the Dispute between Shandong and Jiangsu Provinces (Draft)’ in the report written by Shandong officials to the provincial party committee: ‘…… the discharge channel is controlled by others’. Shandong Province manages the operation of the secondary dam of the Nansi Lake, while Shandong Province cannot completely control the downstream of the Nansi Lake which is divided by the central line of the lake. As a result, Shandong Province would not release water from the upstream to the downstream during the dry seasons. It led to a fatal blow to the crops in Pei County and other counties of the neighboring province on the west side of the Nansi Lake. In the rainy seasons, if Shandong Province opened the secondary dam to relieve itself, the rising water must make the downstream of the Nansi Lake suffer from flooding, especially Pei County. Therefore, water resources as a new spotlight of water conflict have emerged.

In summary, the second period (1953–1980) had the largest number of conflict incidents, 19 times, and the conflict incidents occurred frequently in a short time. Meanwhile, the intensity of conflict was also the greatest during this period. The conflicting parties gradually concentrated from the counties surrounding the Nansi Lake to Pei County and Weishan County over time, and frequent conflict incidents occurred mainly focused on shoaly land and lake production.

The data show that Weishan County and Pei County have had 31 conflicts, which are characterized by frequent conflicts, large scale, and serious casualties since the establishment of Weishan County in 1953. The focus of the conflict was mainly on shoaly land and lake production. According to incomplete statistics, there were 27 conflicts surrounding shoaly land and lake production, accounting for 27/31 of the total. Relevant departments implemented 77 specific policy measures and achieved various results to resolve the increasingly tense conflict situation between the two counties. According to the statistics, there were 33 administrative consultations, resulting in 26 successes, three partial successes, and four failures; for the 19 times policy regulation, 15 were successful, three partially successful, and one failed. Engineering measures were taken 12 times, resulting in six successes, two partial successes, and four failures; administrative law enforcement, 24 times, yielding eight successes, eight partial successes, and eight failures; civil consultation, five times, of which two were successful, three partially successful, and no failures.

It can be seen that administrative consultation and policy regulation have been implemented more, but it is not difficult to find that the success rate of administrative law enforcement measures is 99.99%, which is much higher than the 78.8% success rate of administrative consultation and 78.9% of policy regulation from the data. The reason is the strong law enforcement model under strong supervision. The method of powerful enforcement owns deterrent, which is an important reason for the high success rate of administrative law enforcement. Compared with administrative law enforcement, administrative consultation and policy regulation are less compulsory but more moderate. Administrative consultation is more democratic so that it is applicable in many situations. For now, administrative consultation can take many different forms and are ad hoc in nature. They are fragmented and lack systematic theoretical understanding. Like policy regulation, the administrative consultation is still carried out in a top-down model. The local government easily forms confrontation with people by this way. Due to taking a tough stance and suppressing the legitimate demands of people, the local government will inadvertently intensify the latent conflicts and result in a reduction in the success rate of measures.

Before the establishment of Weishan County in 1953, the two parties in the conflict were mainly the people of Jiangsu Province on the west side of the Nansi Lake and the refugees from Shandong Province. Their conflict was mainly focused on administrative management and the engineering measures were taken most frequently to resolve conflicts in this period. Strong-handed enforcement resolved conflicts through violent suppression and construction engineering measures, but failed to stabilize the masses on both sides and uproot the fundamental differences between the two sides. After 1953, the focus of the conflict changed into competition for resources such as shoaly land and lake production. Administrative consultation and policy regulation began to play an important role in resolving the conflict, and its success rate was high. The reason why it that the solution to deal with conflicts has changed from an absolute top-down model to absorbing the opinions of the masses, which has a certain degree of democracy, so that all stakeholders involved in water conflicts are placed in an open and equal structure. Therefore, there is a better chance for an individual's optimal decision to achieve the most efficient resource allocation, which aligns with the theory of stakeholder wealth maximization. However, the prerequisite for the effective allocation of resources in the market is that the property rights of the resources are clear and transferable. The complex natural attributes and non-exclusive use of water resources make it difficult to define water rights. At the same time, the market approach to resolve water conflicts often prioritizes efficiency and it is difficult to balance fairness, which affects the economic development and social order of the entire region and river basin. Therefore, everyone in the ‘commons’ hopes to get their best interests and will fall into a ‘prisoner's dilemma’ under the situation of absolute civil consultation without the government's mandatory coordination and intervention, which will inevitably lead to failure of the adopted measures.

Based on the text analysis, this thesis divides the focal points of dispute related with the Nansi Lake water conflicts into seven types: administrative management, lake production, shoaly land, water resources, water conservancy, land, and fishery management, with the help of relevant historical records. The policy measures are divided into five categories: engineering measures, administrative consultation, administrative law enforcement, civil consultation, and policy regulation. Based on the above descriptive analysis and cross-correlation analysis, the following optimization suggestions are drawn for the water conflict in the Nansi Lake.

Judging from the historical pattern, the frequency of administrative law enforcement is average. Due to its extremely high compulsory nature, it is completely dominated by the government, and it has achieved better results. However, there are also the following problems: overlapping administrative departments and ambiguous powers and responsibilities. As an agent, the government have asymmetric information and incompletely agreed goals with the public, functional departments and other principals. At the same time, there are high costs of supervision and management (Wang & Chen, 2020). Therefore, the conditions for the use of administrative law enforcement have greater restrictions. At present, the Nansi Lake adopts the ‘river chief system’ (Cheng et al., 2020), which is in line with strong supervision of water resources (Jiang & Yi, 2012). The implementation of the east route project of the South-to-North Water Diversion has strengthened the water control around the Nansi Lake, and realized planned and metered water supply. Although the amount of water intake or outflow is monitored and supervised, the problem of the control of lake water resources still exists. The government should further apply enforcement, relying on the government's coercive force and the deterrence of administrative law enforcement to strengthen policy enforcement, so that the policy can be implemented. Meanwhile the policy will become sounder and contribute to the optimization of the existing policies by coercive force.

Based on the previous data analysis, one can find that among all the measures taken to resolve conflicts around various focal points, the administrative consultation is used the most frequently and has achieved better results than others. Falling short of government coercive power, it has certain limits in resolving various conflicts. However, as the local governments are transforming themselves into ‘service-oriented governments’, the use of administrative consultation measures will be further strengthened because ‘policy makers are required to continuously improve their ability to listen, mediate and resolve differences against the background of increasing conflicts between resource limitation and the diversification of value pursuits’ (Li & Liao, 2012). After all, administrative consultation is a ‘sub-form’ of deliberative democracy. Therefore, in terms of administrative consultation, both sides of Jiangsu Province and Shandong Province should strengthen dialogue and exchanges. By promoting the participation of the public in the decision-making process of the local government, the expression of opinions of the public, the consultation and interaction between multiple interests, and the supervision of the decision-making process by the public in the way of exchanges should be made possible in an institutionalized framework (Bohman & Rehg, 1997). People are expected to find policy solutions from in-depth exchanges. Hopefully all the stakeholders will be satisfied with the results which is derived in the way of administrative consultation to make policy and combine corresponding engineering measures. In doing this, an autonomous order will grow and replace the government coercive power to a certain extent. Local governments can also learn from the experience of South Africa, Canada and other countries, and establish river basin government alliances to coordinate trans-border water rights conflicts by signing agreements or establishing associations and federations. Therefore, the implementation of this policy is reasonable, and cooperation and exchanges between the two parties should be further strengthened.

Based on data analysis, the use of civil consultation in resolving various water conflicts is relatively low and the results achieved are relatively modest. At the face of conflicts of interest in the management of the Nansi Lake, although the State Council approved the establishment of the Yishusi Water Affairs Bureau under the Huai River Conservancy Commission to manage the Nansi Lake, some water intake projects are not under the control of river basin agencies, and they are managed by regional agencies, namely controlled by the water administrative departments of Jiangsu Province and Shandong Province. Yishusi Water Affairs Bureau cannot supervise them, and local governments are easily driven by short-term benefits and their local interests. From a policy analysis point of view, it is necessary to grant administrative law enforcement powers to the River Basin Resources Management Bureau, which is empowered to formulate internal administrative contracts while strengthening the institutional factors of administrative law enforcement and administrative coordination (Ding, 2003). It should also incorporate the idea of self-management of public resources and strengthen the relationship between the masses and water source companies. An awareness of self-regulation and civil consultation will help clarify the positions of all parties in water conflict incidents. A proactive coordination and a thorough analysis of the conflict will ensure the long-term interests of all parties and help improve organizational flexibility and policy implementation.

From the perspective of historical data, when policy regulation is used to resolve various water conflicts, the frequency of use is average, and the results achieved are average. The operation of the public policy system is a dynamic process, including process links such as policy formulation, policy implementation, policy monitoring, and policy termination. The operation of policy regulation requires mutual coordination and cooperation with administrative law enforcement, administrative consultation, and civil consultation. In the policy formulation stage, government departments need to obtain the representations and opinions of all parties before proceeding to work out solutions through administrative consultation and civil consultation; in the implementation stage of policy, a normal and stable operation shall be ensured by administrative law enforcement and the use of national coercive power; in the evaluation and monitoring stages of policy, the government needs to obtain policy feedback through administrative consultation and civil consultation, so that the relevant stakeholders of the policy can fully express their opinions and ensure that their interests are guaranteed by administrative law enforcement. The effective feedback which is ensured by administrative law enforcement is used to judge the rationality of the policy regulation, so that the policy can be appropriately revised, adjusted, and terminated (Liu, 2018). Improving the operation mechanism of the policy regulation is conducive to improving the scientific decision-making of the water administration department and promoting the realization of the expected policy goals.

According to the data, engineering measures are used more frequently in the process of resolving water conflict incidents, but the effects are relatively average. Engineering measures should be used in combination with other types of measures in the implementation process, and the construction management of engineering measures should be strengthened under the condition that the interests of all parties are safeguarded. Construction management must ensure the quality and progress of construction operations, as well as the safety of the construction site, and the economic and social benefits of the construction enterprise (Liu et al., 2013). A careful design of the management systems will ensure a smooth implementation of managerial responsibilities, effective supervision of all the departments involved and a reasonable execution of construction works, which are conducive to the resolution of water conflicts.

The shortage of water resources has caused frequent occurrences of global water conflicts, and continuance of transboundary water rights conflicts. This paper aims to examine the effectiveness of the management policies of water conflict and make optimization suggestions. Therefore, this paper takes the Nansi Lake as an example to discuss the focus of water conflict events and policy measures in the Nansi Lake from the perspectives of time sequence and geographic locality. Through descriptive statistical analysis and cross-correlation analysis of water conflict events in the Nansi Lake, the intrinsic laws of the water conflict incidents in the Nansi Lake and policy implementation are derived from historical data.

In fact, water conflicts around the world are led by competition over natural resources (Buckles, 1999). Through reviewing the existing research on the causes of water conflicts, the likely causes of water conflicts are suggested, including the shortage of water resources, water pollution, and the artificial elements expressed as scarce associated with regulations, governance and corresponding the adoptions of suitable policymaker (Dinar et al., 2011, 2015; Gizelis & Wooden, 2010). As a collection of numerous kinds of water conflicts, the water conflicts in the Nansi Lake have a total of the following focal points of disputes, namely, administrative management, lake production, shoaly land, water resources, water conservancy, land, and fishery administration. This covers the characteristics of most water conflicts in the world. Therefore, the proposed suggestions for the Nansi Lake are also universal to the global water conflict governance. On a more general level, the policy recommendations proposed for the Nansi Lake can provide an effective reference for the policy optimization of global water conflict management. Based on the water conflict problem in the Nansi Lake, the following recommendations are made for the deliberation of global water conflict governance policy: strengthen the government's deterrence in administrative law enforcement and contribute to the optimization of the existing policies by coercive force; promote administrative consultation, realize multi-party equal dialogue and exchanges to make policy solutions which is satisfied by more stakeholders; clarify the position of the parties in civil consultation, ensure group independent coordination and thorough analysis to protect long-term interests of all parties; improve scientific decision-making of the water administration department and effective operating mechanisms of policy regulation as to the realization of the expected policy goals; strengthen construction management in engineering measures, particularly effective supervision of all the departments involved and combine various solutions to ensure effective resolution of water conflicts.

In terms of theoretical contribution, the existing textual analysis approach cannot solve the problem of optimal policy choice for transboundary water conflicts. Considering the Nansi Lake, a typical transboundary lake, as an example, this paper counts the water conflict events that have occurred since 1805, categorizes and analyzes the conflict events, policy choices and policy effects. This paper studies the optimal policy choice of transboundary water conflict combined with descriptive analysis and cross-correlation analysis. We provide a new approach to textual analysis, which is a supplement and sublimation to the application of this research method. With regard to practical contribution, this paper provides a new perspective of optimal policy selection for solving transboundary water conflicts. Through the analysis of specific cases, we have a new understanding of the operation mechanism and effect of different policies to solve transboundary water conflicts. The conclusions of this study will help managers to adopt the best policy to contain the expansion of transboundary water conflicts and better prevent the occurrence of conflicts.

Due to the limited resources and time constraints, this study has only undertaken textual analysis to research the specific data of the historical conflicts in the Nansi Lake and make some suggestions for the water conflict management. There are still many critical areas to be explored in future.

First, the intensity and form of international water conflicts have certain regional characteristics due to different geographical locations, customs, and religious beliefs, and intrinsic laws need further exploration.

Second, this paper uses the text analysis to study the effectiveness of the water conflict management policy in the Nansi Lake through historical documents. However, due to the loss of historical data in the long history, and the incomplete statistical results, in-depth investigation of the data is required to make the classification of focus and policy measures be further clarified.

Third, this article attempts a useful discussion on the effectiveness of the basin water conflict policy. However, with the analysis focused on the Nansi Lake, it has regional limitations. Therefore, the specific basin water conflict should be optimized in accordance with the actual situation.

This work was supported by the Humanities and Social Science Youth Fund of Ministry of Education of China (Grant No. 21YJC790017), National Natural Science Foundation of China (Grant No. 71603125), China Scholarship Council (Grant No. 201706865020), Jiangsu Water Science and Technology Project (Grant No. 2020044), College Students' Innovative Entrepreneurial Training Plan Program (Grant No. 202110319044Z), Young Leading Talent Program of Nanjing Normal University.

Data cannot be made publicly available; readers should contact the corresponding author for details.

The authors declare there is no conflict.