Comprehensive development level of WECEc system in nine provinces of the YRB

Spatio-temporal evolution analysis

From the perspective of time, from 2013 to 2022, the regional average of CAI of WECEc system in the nine provinces and regions of the YRB increased from 0.3072 to 0.3805, with an increase rate of about 23.9%, showing a fluctuating upward trend in general, which is consistent with the research results of Shi and He (2024)39. This growth trend shows that the integrated management and improvement of the YRB in terms of water resources security, energy security, carbon emission reduction and ecological protection has achieved remarkable results. From 2020 to 2021, the average level of CAI rose from 0.3777 to 0.3989, an increase of 5.6%, reflecting the gradual effect of policies on ecological protection and high-quality development in the YRB in recent years (Fig. 6).

From the spatial perspective, the comprehensive development level of the nine provinces of the YRB has significant spatial heterogeneity among provinces. The CAI level of the middle and upper reaches of Sichuan, Inner Mongolia, Shaanxi, Shanxi and Shandong provinces has always been higher than the regional average of the nine YRB provinces, while the CAI value of the lower reaches of Qinghai, Gansu and Ningxia provinces has been below the average for a long time in this decade. Sichuan’s CAI increased from 0.4655 in 2013 to 0.5412 in 2022, an increase of about 16.3%. Despite the decline in 2022 compared with 2021, its CAI value is still in a leading position in the YRB. Inner Mongolia’s CAI increased from 0.4638 in 2013 to 0.5548 in 2022, an increase of about 19.6%. As an important province in the middle reaches of the YRB, the improvement of Inner Mongolia’s CAI is mainly due to the optimization of the energy industry and the promotion of ecological protection projects. Shaanxi’s CAI increased from 0.3595 in 2013 to 0.4527 in 2022, an increase of about 25.9%. The implementation of the strategy of “Ecological protection and high-quality development in the Yellow River Basin” has a certain promoting effect on the improvement of the CAI of Shaanxi Province. The CAI of Shanxi increased from 0.3066 in 2013 to 0.3902 in 2022, an increase of about 27.3%. As a major energy province, remarkable achievements in energy structure transformation and ecological restoration have promoted the comprehensive development of Shanxi Province year by year. Shandong’s CAI increased from 0.2673 in 2013 to 0.3594 in 2022, an increase of 34.5%. Shandong is located in the lower reaches of the YRB, and the rapid improvement of the CAI is mainly due to the modernization of agriculture and the optimization of energy structure. In contrast, the CAI of Qinghai, Gansu and Ningxia is relatively low, although the overall improvement, but the increase is relatively small. The CAI of the three provinces from 2013 to 2022 was 0.2865, 0.2535 and 0.1763 respectively, which were lower than the average of 0.3461 in the YRB, reflecting the problems of low utilization efficiency of key basic resources such as water resources and energy, insufficient carbon emission control and fragile ecological environment in the upper Yellow River region where the three provinces are located. There may also be a waste of resources or mismanagement.

From the perspective of spatiotemporal correlation, the differences in the comprehensive development level of the WECEe system among the nine provinces/autonomous regions in the YRB are the results of the joint action of resource endowments, industrial structures, and policy responses. In the temporal dimension, the significant improvement from 2020 to 2021 is closely linked to the dual carbon goals and the basin’s ecological protection strategy, reflecting the driving role of policies. However, the fluctuating trend also reveals the issue of policy dependence. Spatially, central and upper-reach provinces have led in development by relying on resource advantages and early-initiated industrial upgrading. Shandong, a lower-reach province, has achieved breakthroughs through the optimization of agricultural and energy structures. In contrast, upstream provinces such as Qinghai, Gansu, and Ningxia have lagged in development due to high water-consuming industries, inefficient energy utilization, and insufficient ecological compensation. This indicates that future governance of the basin needs to strengthen differentiated positioning and establish cross-regional resource allocation and benefit-sharing mechanisms to promote the basin’s transition from local optimization to overall synergy.

Fig. 6 Change trend of the CAI value of the nine provinces of the YRB from 2013 to 2022. Full size image

Analysis of subsystem development level

From the perspective of the water resources subsystem, the CAI of the water resources subsystem shows a fluctuating upward trend from 2013 to 2022. The average value of CAI of water resources subsystem of the nine provinces in the YRB increased from 0.1272 in 2013 to 0.1457 in 2022, an increase of about 14.5%. Among them, the CAI value of water system peaked at 0.1673 in 2021 and decreased slightly in 2022. This overall upward trend is due to the efforts made by provinces in recent years to improve the efficiency of water use according to local conditions, such as the improvement of water infrastructure in Sichuan province and the implementation of the Outline of the National Medium and Long-term Plan for Food Security in Henan Province, a major agricultural province. The development trend of the water resources subsystem in the past ten years is the most consistent with the overall development trend of WECEc system, which indicates that the improvement and promotion of water resources utilization capacity plays a crucial role in the benign development of WECEc system.

From the perspective of the energy subsystem, the CAI of this subsystem showed a slow and steady upward trend from 2013 to 2022. The regional mean of the energy subsystem increased from 0.0680 in 2013 to 0.0730 in 2022, an increase of about 7.4%, which is the least statistically significant of the four subsystems. Among the nine provinces in the YRB, Inner Mongolia Autonomous Region and Shaanxi Province are the major energy production and consumption provinces. The application of clean energy technology and optimization of energy structure in each province have played a certain role in promoting the improvement of regional energy security level. However, the sustained and rapid development of heavy industry, coal and chemical industry and other energy-consuming industries has slowed down the rise rate of the CAI of energy system. In the context of the dual carbon goals, the endeavor to restructure the energy system and optimize corresponding policies in the YRB remains a formidable and protracted challenge.

From the perspective of carbon subsystem, the CAI of this subsystem shows a steady upward trend between 2013 and 2022. The average CAI of the subsystem in the nine provinces of the YRB rose from 0.0779 in 2013 to 0.0992 in 2022, an increase of about 27.3%. Taking Shanxi Province and Shandong Province as examples, the CAI of carbon emission subsystem in Shanxi increased from 0.0414 in 2013 to 0.0556 in 2022, with an increase of about 34.3%. The continuous growth of total carbon emissions in Shanxi Province during this decade may be related to factors such as increased energy consumption and expansion of industrial activities. The CAI of Shandong’s carbon subsystem increased from 0.0441 in 2013 to 0.0525 in 2022. Shandong is an important industrial province in the lower reaches of the YRB, with heavy chemical industry (such as steel, chemical industry, building materials, etc.) accounting for a relatively large proportion and high carbon emission intensity, resulting in an increase in the overall carbon emission level. It also shows that the economic growth of Shandong Province still relies on the high-carbon model, and has not yet realized the decoupling of economic development and carbon emissions.

From the perspective of the ecological environment subsystem, the CAI of this subsystem showed a significant upward trend from 2013 to 2022. The mean value of ecological environment subsystems in the nine provinces of the YRB increased from 0.0341 in 2013 to 0.0625 in 2022, an increase of 83.3%. This shows that with the improvement of regional ecological environment and the implementation of the “Three-North Shelterbelt Project” and “Desertification Prevention and Control Project”, the overall optimization effect of ecological environment is obvious. The ecological environmental subsystem CAI of Qinghai Province and Gansu Province has increased by 51.6% and 100% respectively in the past ten years, which is inseparable from the relevant departments in the upper reaches of the Yellow River to effectively coordinate the integrated protection and systematic management of “mountains, rivers, forests, fields, lakes, grasses and sand”.

However, complex synergistic and restrictive relationships exist among the subsystems. The development of the water resources subsystem provides fundamental support for energy production and ecological restoration. For example, efficient water resource utilization can meet the cooling water demand in energy extraction processes, reducing pressure on the ecological environment. Conversely, improvements in the ecological environment subsystem help conserve and purify water resources, forming a benign cycle. However, the contradiction between the energy subsystem and the carbon subsystem is particularly prominent. Energy system growth driven by high-energy-consuming industries directly exacerbates carbon emissions, offsetting part of the achievements in ecological environment governance and indirectly impacting the water resources system, for instance, water pollution issues during energy extraction. Such imbalanced relationships among subsystems necessitate strengthening the concept of multi-system collaborative governance in the sustainable development planning of the YRB. It is essential to comprehensively promote the economical and intensive use of water resources, low-carbon transformation of the energy structure, precise control of carbon emissions, and protection of the ecological environment system, breaking down development barriers among subsystems and building a new development pattern of mutual promotion and symbiosis.

Development of CCD of WECEc system in nine provinces of the YRB

Spatial and Temporal distribution characteristics

In the time dimension, it is noted that from 2013 to 2022, the mean CCD of the basin gradually increased from 0.5061 to 0.5673, and the overall WECEc system of the YRB showed a steady growth trend, with an annual growth rate of about 1.2%. Among them, the growth rate of CCD from 2013 to 2016 was relatively low, with an average annual growth rate of about 1.1%; From 2017 to 2021, the growth of CCD accelerated, with an annual growth rate of 1.5%; In 2022, the overall CCD of the YRB decreased slightly, and this downward trend is related to the increased pressure on the ecological environment caused by economic development in some regions.

In spatial dimension, the CCD of Inner Mongolia, Sichuan, Shaanxi and other upstream provinces is generally high, and the coordination type is mostly “General Coordination”, forming a high-value agglomeration area of coupling coordination. This level of coordination reflects the better balance between ecological protection and economic development in the upstream regions, as well as the remarkable results achieved in ecological protection and economic transformation in these regions. The CCD of Shanxi, Gansu, Qinghai and other provinces located in the middle reaches is mostly at the medium level, and the coordination type is concentrated as the state of “Near Imbalance” gradually improved to “Primary Coordination”, and it is represented as the median accumulation area of coupling coordination. It shows that these regions have made some progress in coordinated development, but still need to be further optimized. In the downstream provinces of Shandong and Henan, although the CCD is low, most of them are of the “Near Imbalance” type, which is reflected in the accumulation area of low coupling coordination value, but the CCD has shown a steady rising trend in the past ten years, indicating that these regions are facing greater pressure on water resources, energy and ecological environment in their economic development. The improvement in coupling coordination of multidimensional systems is slow (Fig. 7).

From a comprehensive perspective of spatiotemporal evolution, the changes in the coupling coordination degree of the WECEe system in the YRB not only reflect the divergent development paths across regions but also mirror the periodic effects of policy implementation. Temporally, the accelerated growth period from 2017 to 2021 closely aligns with the policy cycle of strengthening ecological civilization construction and promoting green development during China’s “The thirteenth Five-Year Plan” (2016–2020), demonstrating that top-down policy design has significantly propelled the coordinated development of the systems. However, the brief decline in 2022 serves as a warning that extensive economic recovery may backfire on the ecological environment, underscoring the critical need for policy continuity and precision. Spatially, the gradient differences in coordination levels among the upper, middle, and lower reaches are deeply rooted in regional resource endowments. Upper-reach provinces, supported by abundant ecological resources and low development intensity, hold a natural advantage in ecological protection. Middle-reach regions, as energy and chemical industry hubs, exhibit slow coordination improvement due to lagging industrial transformation. Lower-reach areas, characterized by dense populations and industrial agglomeration, face the dilemma of resource-environmental carrying capacity nearing saturation. This spatial heterogeneity suggests that it is urgent to promote the formation of a development pattern of complementary advantages and coordinated progress in the entire basin.

Fig. 7 Spatial and temporal distribution of CCD in nine provinces of the YRB. The base map was obtained from the standard map service system of the ministry of natural resources of China, map review number: GS(2022)1873. The maps were generated using ArcGIS software version 10.7 (https://www.arcgis.com/index.html). Full size image

Provincial variation trend

Most of the nine provinces showed a steadily improving form of CCD (Fig. 8). Among them, Inner Mongolia Province, which has the highest mean value of CCD, presents a fluctuating growth trend. The coordination degree decreased by 3.87% from 2013 to 2015, and gradually increased at a growth rate of 2.53% every year from 2015 to 2021, reaching a peak of 0.7319 in 2021. However, the CCD decreased slightly in 2022. The potential negative impact of energy development and carbon emissions on water resources and ecological environment should be vigilant. The average CCD of Ningxia Hui Autonomous Region is 0.3941, which is the lowest among the nine provinces in the YRB, and its CCD value rises from 0.3753 in 2013 to 0.4071 in 2022, with an average annual growth rate of about 0.80%, which is related to the realistic basis of Ningxia’s shortage of water resources, high energy dependence and great pressure on ecological environment. Ningxia should strengthen the protection of water resources, promote the low-carbon energy structure, reduce carbon emissions, and strengthen ecological and environmental governance.

Fig. 8 Variation trend of CCD in nine provinces of the YRB. Full size image

Factors hindering the CCD of WECEc system in nine provinces of the YRB

According to the calculation results of OD, the regional mean represents the obstacle degree of the YRB. In this paper, the top 8 obstacle factors are selected and analyzed according to the order of OD of indicator layer from high to low (Fig. 9). In the YRB, the ranking of the top 8 degrees of influence on the CCD of the WECEc system is as follows: Total water resources > Per capita carbon storage > Coal production > Water production modulus > Carbon storage of forest and grass > Total energy production > Carbon sink of forest and grass vegetation > Domestic water consumption.

Fig. 9 Heat map of obstacle factors diagnosis for WECEc system in the YRB. Full size image

The OD of total water resources is increasing by 1.5% per year and will peak in 2022 (14.33%). It is speculated that this is related to the fluctuation of precipitation and the increase of economic development demand. The increasing OD of this index directly reflects the worsening water shortage problem in the YRB, indicating the slow improvement of regional water resources utilization efficiency and the persistent water pressure in agriculture and industry. The OD of per capita carbon storage increased from 10.67% in 2013 to 10.71% in 2022, with a slow upward trend, indicating that the improvement of carbon sink capacity is limited. This is related to low vegetation coverage, overgrazing and development in ecologically fragile areas of the YRB. Coal mining and thermal power industry development in Inner Mongolia, Shanxi and other places will also lead to increased carbon emissions and weaken carbon sink capacity, thus affecting regional coordinated development. The annual average value of OD of coal production is 8.71%, and the annual growth rate of this variable is about 0.3%. This result may be due to the increase of carbon emission pressure caused by excessive dependence on coal economy in coal-rich areas. Meanwhile, the long coal industry chain involves high-carbon emission industries such as coking and thermal power, which will aggravate the pressure on the ecological environment subsystem. The OD of the water production modulus increased from 7.37% in 2013 to 8.21% in 2022, with an average annual growth rate of about 1.2%, reflecting the increasing pressure of water resources development year by year. The proportion of agricultural water in Henan Province is more than 60%, the development of water resources is over, the ecological water is squeezed, and the low water production modulus leads to insufficient irrigation water and aggravates the shortage of water resources. The OD of carbon storage and carbon sink capacity of forest and grassland vegetation on the system is about 7%, which is related to the degradation of grassland caused by overgrazing in the province with large animal husbandry, and the decrease of carbon sink capacity indirectly caused by the reduction of forest and grass vegetation caused by farmland expansion in the province with large agriculture. The OD of total energy production decreased from 6.5% in 2013 to 6.43% in 2022, showing a slow downward trend. The total output of energy industry in coal-dominated energy provinces is higher, and the hydropower development in Qinghai, Sichuan and other places is more intensive, which leads to the overall energy production as an obstacle factor affecting the coordinated development of regions. The annual average value of OD of domestic water is about 6.12%, which is related to the increasing demand for domestic water in densely populated areas, aging and imperfect water supply facilities in urban and rural areas (Fig. 10).