Coupled coordination of water resources–economy–ecosystem complex in the Henan section of the Yellow River basin Open Access

Social and economic development create conflicting human demands for water resources, economic growth and environmental conservation. Balancing these demands by coordinating the development of water resources, economic growth and environmental conservation has become an area of intense research in sustainable development (Zhao 2016) to the extent that coordinated development of water resources, economic growth and environmental conservation has become a long-term goal of human development (Liu et al. 2007). China has formulated and issued a number of policies for coordinated development and green development at the macro-level in the recent past, which have great strategic significance in building a resource-conserving and environmentally friendly society (Zuo et al. 2017; Yang et al. 2019).

Haken (1978) first proposed the concept of synergetics in the 1970s. The System of Environmental-Economic Accounting (SEEA) introduced by the United Nations in 1993 (Smith 2007) is a theoretical system that integrates multiple disciplines and methods such as political science, ecology, and economics. Costanza et al. (1997) argued that ecosystem services represent a part of the total economic value of the Earth and laid a theoretical foundation for the study of resource–ecological–economic systems as entities. Mutisya & Yarime (2014) investigated the extent of coupling and the degree of coordination between Kenya's resources, the natural environment, society and economy and suggested that management of the natural environment and governance of society should be strengthened to increase the degree of coupling.

As research develops, more and more researchers are identifying the degree of coupling and the extent of coordination within composite systems. F. Q. Wang et al. (2022) modeled the degree of coupling and extent of coordination to quantify the coupled development of water resources, the economy and ecosystem in the Beijing–Tianjin–Hebei region from 2006 to 2019 and to provide a theoretical grounding for decision-making in the region. Wen & Wen (2019) also modeled the degree of coupling and extent of coordination in investigating symbiotic relationships and coordination between water resources, the economy and ecosystem in 18 key provinces (cities, districts) to support the Belt and Road Initiative. They created a system of evaluation indexes for the three subsystems suitable for use in assessing key areas temporally and spatially. The evaluation index system they developed used comprehensive subjective and objective weighting to calculate the weights of indicators at all levels and calculated the degree of coupling and the extent of coordination within a system. Based on the two dimensions of endogenous power and external dynamics, Zhang et al. (2022) introduced a fixed-effect model to measure the driving factors of water–economic and society–ecological environment coupling coordination in Gansu Province from 2010 to 2019. The analysis of regional water–economy and society–ecological environment coupling and their coordinated development is of great significance to strengthen the macro-management of natural resources and economic and social systems and promote regional sustainable development. Du et al. (2022) constructed the evaluation model for the coupling coordination of water resources, socio-economy, and ecological environment and quantitatively analyzed the development status of subsystems and their coupling systems from 2005 to 2019 of specific regions (northeast, north China, and northwest) and administrative units (provinces and municipalities directly under the central government).

With the deepening of research, scholars began to study the future coupling coordination of composite systems. Zhou et al. (2016), Ling & Yu (2016) and Cai et al. (2020) used a GM (grey model) to predict coupling and coordination in different regions and analyzed them in terms of the future development of the regions. Cao (2015) modeled the degree of coupling and extent of coordination for the development of composite systems in the western region of China using a back-propagation (BP) neural network and produced a roadmap to expedite construction in the region. Luo et al. (2022) empirically analyzed the co-evolution of the water–energy–food complex in the Yellow River basin from 2010 to 2019 and used an ARIMA model to predict the degree of coupling and extent of coordination. Wang (2019) used system dynamics to measure and simulate the coordinated development level of the energy–economy–environment (3E) system in Anhui Province and analyzed in depth the relationship between the three, which had important theoretical and practical significance for making developed scientific decisions and promoting regional sustainable development.

At present, there are very few relevant studies that evaluate or predict the coupling and coordination of water resources, the economy, and the ecosystem in the southern part of the Yellow River basin and Henan Province, which is located in the lower reaches of the Yellow River but occupies an important position in the entire Yellow River basin. This study aims to fill this gap and provide decision-making information for the problems of lagging economic development, scarcity of water resources, and serious pollution of the local natural environment in the southern part of the Yellow River basin. A comprehensive index system for the three subsystems of the water resources–economy–ecosystem complex was established. We initially established an index for each factor in each system and weighted the indexes to form a comprehensive subsystem index. Then, the water resources–economy–ecosystem model was developed to calculate the degree of coupling and extent of coordination between subsystems. We used grey relational analysis to analyze and calculate the extent of the influence of each factor index on the degree of coupling and the extent of coordination and produced a comprehensive index for the entire water resources–economy–ecosystem complex in the Henan section of the Yellow River basin. An SSA-BP model was used to verify the comprehensive index in order to ensure the prediction accuracy of the system model in order to provide theoretical support for the coordinated development of water resources, economic and social growth, and the natural environment in the Henan section of the Yellow River basin.

The Yellow River is the second longest river in China and one of the longest rivers in the world. The Yellow River basin is in a temperate zone and a plateau climate zone. Annual sunshine is 2,000–3,300 h; annual rainfall is unevenly distributed, with an average in the range 200–650 mm; the average frost-free period in the upper, middle and lower reaches of the river is in the range 20–200 d (Xiao et al. 2020). The Henan section of the Yellow River basin flows through nine cities in Henan Province (Zhengzhou, Kaifeng, Luoyang, Anyang, Xinxiang, Puyang, Sanmenxia, Jiyuan and Jiaozuo) in the lower reaches of the river. The Henan section of the Yellow River basin is extremely turbid due to the enormous amount of entrained sediment transported by the river, and the region faces problems of sediment deposition, changes in the river course, and the ‘hanging river on the ground’ (a phenomenon in which the deposited sediment has raised the level of the river bed to be above the river banks) that have not been completely resolved. The risk of flooding has increased in the region due to climate change and extreme weather events. Urban and industrial development in the Henan section of the basin has introduced problems associated with low quality and low efficiency that are characteristic of the energy and chemical industry; pollution from raw materials, agriculture and animal husbandry is obvious, and there are few industrial clusters that are strongly competitive.

Research into the combined water resources–economy–ecosystem complex has not yet provided a single unified index that accurately represents the complex. Following the principles and methods of index construction (Qaiser et al. 2017; Held et al. 2018; S. S. Wang et al. 2022), we constructed an index intended to reflect the state of the water resources–economy–ecosystem complex of the Henan section of the Yellow River basin. The first stage of developing the index was to identify the interactions between the various indicators shown in Table 1.

The data used in this study come from the 2000–2019 publications of the China Statistical Yearbook, Henan Provincial Statistical Yearbook, Henan Province Water Resources Bulletin, Henan Province Environmental Status Bulletin, the 2000–2019 Statistical Yearbooks of cities in the Henan section of the Yellow River basin, Resources Bulletin, and the 2000–2019 Yellow River Water Resources Bulletin.

We used data for the current state of water resources, economic development and the natural environment in cities in the Henan section of the basin and combined it with historic data from previous studies (Diao et al. 2020; Wang & Hu 2020; Wang et al. 2021). We also qualitatively categorized the degree of coupling and the degree of coupling coordination in coordinated development based on indicator values (Table 2).

Grey relational analysis is a very active branch of grey system theory. The underlying idea of the method is to determine how close is the relationship between different sequences to the geometric shape of the sequence curve. The sequence is converted into a continuous segmented polyline, and then a model that measures the degree of association is created according to the geometric characteristics of the polyline (Liu et al. 2013). In order to examine the extent of the influence of each index on the degree of coupling coordination, the degree of coupling coordination was selected as the reference sequence, and each index was used as a comparison sequence.

The sparrow search algorithm (SSA) is a swarm intelligence optimization algorithm developed by Xue (2020). The sparrow search algorithm uses the foraging and anti-predation behaviors of sparrows as the basis of a mathematical model to simulate the behavior of sparrows in nature. The specific rules are as follows.

• (1)

  The finder (the sparrow that finds a food source) has a high energy reserve and provides the joiner (a freeloading sparrow that observes the finder) with an area and direction for foraging. If either sparrow observes a predator, that sparrow will chirp an alarm signal. When the alarm value is greater than the safe value, the finder will take the joiner to another safe area for foraging.

• (2)

  The identities of finders and joiners are dynamic. One sparrow becomes a finder and another sparrow becomes a joiner. Joiners can search for and follow the finder that provides the best food and then get food or forage from around the finder. In order to increase their predator avoidance rate, some joiners may constantly monitor the finder and compete among themselves for food resources.

• (3)

  The lower the energy of the joiners, the worse the foraging position they are in, in the overall population.

• (4)

  When aware of danger, sparrows at the fringes of the flock move quickly to a safe area to gain a better position, while those in the middle of the colony move randomly to get closer to other sparrows.

The specific algorithm based on this behavior is as follows.

The comprehensive index of the water resources subsystem clearly had an increasing trend in 2003, a significant decreasing trend in 2008 and 2012 and a decreasing trend in 2016. These trends occurred because precipitation in the Yellow River basin was significantly higher in 2003; average precipitation was 555.6 mm. Total precipitation volume in 2003 was 441.70 km³. In terms of regional precipitation distribution, the region between Sanmenxia and Huayuankou had the greatest precipitation. In 2008, the surface water and water resources in the Henan section of the Yellow River basin decreased by 43.7% compared with the long-term average. The Qinhe water system decreased by >50%. In 2012, the per capita water resources in Henan Province decreased significantly compared with 2011. At the end of 2016, the funnel-shaped Anyang–Puyang area in the Henan section of the Yellow River basin expanded by 80 km², and the subsurface depth to groundwater at the center of the funnel increased by 1.84 m due to excessive groundwater exploitation that destroyed the groundwater balance; the groundwater level continues to decline.

Since 2005, the comprehensive index of economic subsystems has increased sharply. Since the introduction of the Henan Province Tenth Five-Year Plan, Henan Province has implemented the national macro-control policy and made great efforts to strategically adjust its economic structure. The region has become significantly stronger economically; per capita GDP increased from ¥200.188 million CNY in 2005 to ¥680.599 million CNY in 2019. Henan Province has completely transformed itself from a large agricultural province to a large economic/industrial province.

The Henan section of the Yellow River basin could be characterized prior to 2010 as being static and having a large population, weak infrastructure and unbalanced development. The environmental situation was dire, and basic capacity lagged behind other parts of China. The economy of the Henan section of the Yellow River basin has developed rapidly since then, as has environmental protection. It is still not perfect, and the comprehensive index of ecological subsystems shows a decreasing trend. In 2015, environmental protection in the Henan section of the Yellow River basin was still severely strained, but resource and environmental constraints were tightened. However, compared with previous years, there has been overall improvement and there has been good progress in the implementation of environmental protection specified in the 12th Five-Year Plan. During the implementation of environmental protection identified in the 13th Five-Year Plan, attempts were made to build an ecological protection system, with noticeable effect. In 2019, the comprehensive index of the ecological subsystem in the Henan section of the Yellow River basin showed a significant increasing trend.

The degree of coupling was at a high level from 2000 to 2019 but it began to show a decreasing trend after 2011. This was due to the rapid development of the economy in Henan Province after 1998. Environmental protection and water resource management were neglected in the early stage of economic development. In 2013, the state increased protection of the environment and control of water resources, but protection and control did not develop at the same speed as the economy, and so the degree of coupling decreased. However, the degree of coupling showed an increasing trend in 2019, which indicates that environmental governance has been effective.

From 2000 to 2002, coupling coordination was classed as reluctant. After 2010, development in the Henan section of the Yellow River basin was more coordinated, and this classification became intermediate. Overall, the degree of coupling coordination has become good. The process guiding this change was as follows. The Yellow River had 19 no-flow events from 1972 to 1999, and the ecological balance of the river basin was seriously upset. After the completion of the Xiaolangdi project, the ecological balance of the Yellow River basin began to recover. The degree of coupling coordination was <0.6 from 2000 to 2002, and the basin was in a state of barely coordinated development. From 2003 to around 2009, the water resources–economy–ecosystem complex was transformed into a state of primary coordinated development because over-development of the economy had some effect on water resources and the natural environment. For example, secondary manufacturing in Henan Province during this period increased annually. In 2006, secondary manufacturing in Henan Province accounted for 70.70% of all manufacturing; this exceeded the national average by 1.67%.

The natural environment subsystem has gradually shifted to a stage of intermediate coordinated development. The state has done a lot of work to optimally allocate environmental and water resources, and Henan Province has implemented in-depth reforms. Examples are the implementation of the river-chief system, in which a single entity has responsibility for water quality for a particular catchment or reach, the establishment of a water and soil loss prevention system, the construction of regional water diversion projects, and better use of precipitation in the region; these activities are all related. The problem being addressed is, given the extreme shortage of water resources in the Henan section of the Yellow River basin, how can various regions all achieve effective economic development? There are no universal solutions: environmental protection is the main area for future research.

Factor identification showed that the indicators of the water resources subsystem accounted for 34.30%, of the system total, the economy subsystem indicators accounted for 32.55%, and the natural environment subsystem indicators accounted for 32.15%. The most important factor in the coordinated development of sector coupling was the influence of economic, social and environmental indicators on the degree of coupling coordination. Water resources are an indispensable basic natural resource in high-quality development of the Henan section of the Yellow River basin. The comprehensive coordination of local water resource use, external water transferred into the region and unconventional water sources with improved water conservation and water use efficiency is key to sustainably developing the Henan section of the Yellow River basin, and it is an important measure for high-quality development of water resources–economy–ecosystem.

Water consumption has continually increased in the Henan section of the Yellow River basin with the rapid economic and social development in the province, and the negative effects of human activity have become increasingly obvious. Limited water resources seriously restrict sustainable development of the economy in Henan Province. Much research has been directed toward finding the best balance between social and economic development, maintaining the natural environment and the use of water resources. The Henan section of the Yellow River basin was the research area for this study, in which we identified problems and deficiencies in the current research and developed a model for the coordinated development of the water resources–economy–ecosystem coupling. Our research supports the following conclusions:

• (1)

  The comprehensive index of the water resources–economy–ecosystem complex in the Henan section of the Yellow River basin shows that the degree of coordination steadily increased over the period. The overall variation in the index was small. The comprehensive index of the economic subsystem also increased, and the comprehensive index of the natural environment subsystem varied greatly in contrast with the other two subsystem indexes. The degree of coordinated development in the water resources–economy–ecosystem coupling moved closer to being optimal annually from 2000 to 2019 as it changed gradually from the coordinated development category of barely coordinated development to good coordinated development. The degree of coupling coordination in the water resources–economy–ecosystem complex reached the stage of good coordinated development.

• (2)

  The most important factors affecting coupling coordination were water modulus (factor 4), total water consumption (5), modulus of water supply (9), primary production ratio (12), sewage–runoff ratio (20), river sediment transport (26) and environmental water use rate (27). Future development and use of local water resources, water transported into the region and unconventional water sources should be coordinated to reduce water use and increase water use efficiency. Other necessary improvements include improving water and sediment control to reduce the conflict between supply and demand of water resources; building sewage purification lagoons, artificial wetlands and infrastructure to intercept nitrogen and phosphorus to prevent environmental degradation; constructing water purification plants; and increasing water recycling resources. These measures support the overall goal of promoting high-quality economic and social development and protecting the natural environment.

• (3)

  The SSA-BP model showed a steady increasing trend in the degree of coupling coordination of the water resources–economy–ecosystem complex in the Henan section of the Yellow River basin. The model predicted a good coordination from 2020 to 2025 with a large amount of development. The model predictions also provide the basis for rational allocation of resources, improved efficiency in resource utilization, the avoidance of resource waste, and the prevention of resource imbalance due to rapid urban development.

Due to the restricted study period, only 20 years of data were collected in the data collection process, making the coupling coordination evaluation in this paper lack a certain degree of completeness, thus limiting the prediction of coupling coordination. Future research should combine the current situation of the Yellow River basin and fully consider other influencing factors affecting the coupling coordination of water resources, the economy, and the ecosystem to broaden the scope and increase the depth of research to achieve not only the coordination of the water resources–economy–ecological environment coupling system of the entire Yellow River basin but also the sustainable, high-quality, and stable development of the Yellow River basin.

This work was financially supported by the General Project of National Natural Science Foundation of China, No. 52079051, Key Scientific Research Project of Henan Province Colleges and Universities, No. 22A570004 & 23A570006, Fund of Innovative Education Program for Graduate Students at North China University of Water Resources and Electric Power, China, grading no. YK-2021-43.

S.W. (Professor) wrote and revised the manuscript, J.Y. (M.S. student) analyzed the data, A.W. (Associate Professor) revised the manuscript, T.L. for data visualization, Y.Y. to collect and organize data.

Data and materials are available from the corresponding author upon request.

The authors declare there is no conflict.