Weihe River basin (34°–37°N, 104°–110°E; Figure 1), originating from Niaoshu Mountain in Gansu Province, flows into the Yellow River basin in Shaanxi Province. It lies in the north of Qinling Mountain, south of Liupanshan Mountain, the east of Loess hilly and gully region, and the west of Guanzhong Plain. Located in the warm temperate zone, WRB in Shaanxi Province has a subhumid continental climate, with an annual mean temperature of 7.8–13.5°C and an annual precipitation of 500–800 mm (Zhao et al., 2016). The main stream of WRB in Shaanxi Province, a length of 502.40 km, covers a drainage area of 67,108 km², accounting for 50% of the total drainage area of the Yellow River basin in Shaanxi Province. The average annual runoff of the whole river is 1.04 × 1010 m³, of which the runoff in Shaanxi Province is 6.27 × 109 m³, with the flooding period (July to September) accounting for about 60% (Deng et al., 2020).

The Weihe River is the mother river of Shaanxi, related to the rise and fall of economic and social development in Shaanxi Province. The core of Guanzhong–Tianshui economic region, WRB, plays an important role in the western development strategy of China. By the end of 2018, the population of the study area grew to 2.45×10⁷ people and GDP 9.87×10¹⁴ yuan (Shaanxi Provincial Bureau of Statistics, 2019). The total water resources quantity in the study area, 7.25 × 109 m³, only accounted for 1.95% of that in Shaanxi Province. Only covering one-third of the land area of Shaanxi Province, WRB in Shaanxi Province discharged over three-fourths of the wastewater in Shaanxi Province. The water supply and water consumption of WRB in Shaanxi Province compose more than half of Shaanxi Province, 57.50% and 59.37%, respectively (Shaanxi Province Department of Water Resources, 2018). This study involves five cities on the main stream of WRB in Shaanxi Province, including Xi’an, Tongchuan, Baoji, Xianyang, and Weinan.

In recent years, remarkable changes have taken place in WRB with the intensification of human activities and the rapid development of the regional economy and society. However, multiple issues have attracted public concern, such as insufficient water resources, aggravated water pollution, overexploitation of groundwater, and incomplete containment of soil and water loss. Therefore, the study on sustainable development of WRB in Shaanxi Province is of great significance for promoting green development of the economy and society in Shaanxi province.

The indicator system was based on the United Nations Sustainable Development Goals (SDGs) and China’s National Plan on Implementation of the 2030 Agenda for Sustainable Development. To clarify the status of RBSD, this article regarded water resources as the core, the basin as a research space, and the complex system composed of human and nature in the basin as a research object. According to the construction principle of indicator system and covering the main environmental and socioeconomic issues contained in the concept of sustainable development with Chinese characteristics, the evaluation indicator is divided into a hierarchical system consisting of target layer (A), system layer (B), subsystem layer (C), and indicator layer (D).

The indicators were chosen for systematicness, completeness, representativeness, and accessibility. In terms of the actual situation, the water resource characteristics, and the evaluation content of WRB, 31 indicators were selected to construct the indicator system of RBSD (Table 1).

To eliminate the magnitude difference among the data, the deviation standardization formula is adopted for each indicator, so that the results are all within the range of (0,1).

Positive Indicator

Y i j = x i j − m i n ( x i ) m a x ( x i ) − m i n ( x i ) . (1)

Negative Indicator

Y i j = m a x ( x i ) − x i j m a x ( x i ) − m i n ( x i ) . (2) Here, x_ij and Y_ij are the original and normalized values of the ith indicator in the year j, respectively.

In information theory, entropy is a measure of uncertainty. According to the characteristics of entropy, the discrete degree of indicator layer can be measured by calculating the entropy value. The larger the discrete degree of indicator, the greater the influence of indicator on a comprehensive evaluation. The entropy method is used to quantify the information of each indicator with the Shannon entropy (Shannon, 1948). Information entropy is employed to calculate the weight of each indicator layer to achieve an objective quality evaluation.

Assuming that there are m evaluation objects and n evaluation indicators, a matrix A with n rows and m columns can be established: A = ( x i j ) n × m . (3) The proportion Z_ij of the ith indicator in the year j is given as follows: Z i j = Y i j ∑ i = 1 m Y i j . (4) The entropy k_i of the ith indicator is as follows: k i = − 1 I n m ∑ i = 1 m ( z i j I n z i j ) . (5) The redundancy g_i of the information entropy of the ith indicator is as follows: g i = 1 − k i . (6) The weight w_i of each indicator is calculated as follows: w i = g i ∑ i = 1 n g i . (7) The comprehensive evaluation of RBSD is calculated as follows: R B S D = ∑ i = 1 n Y i j W i . (8)

In the process of sustainable development evaluation, it is not only necessary to measure the level of RBSD but also to understand the critical factors that affect RBSD. Therefore, the obstacle degree model (Chen Y. et al. (2020), Fan and Fang (2020)) is introduced to analyze the obstacle factors of RBSD so as to carry out the pathological diagnosis in a practical application. The formula is as follows: P i j = 1 − x i j , (9) Q i j = P i j W j ∑ j = 1 n P i j W j , (10) where Q_ij represents the obstacle degree of the ith indicator in the year j, and P_ij is the deviation degree of indicator i in year j.

In view of accessible and limited data, this article chose 2009 to 2018 as the research period and five cities of WRB in Shaanxi Province were selected as samples to establish a comprehensive indicator system for the sustainable development of WRB in Shaanxi Province. Data were collected from the China Urban Statistical Yearbooks (2010–2019), Shaanxi Statistical Yearbooks (2010–2019), and Shaanxi Water Resources Bulletins (2009–2018). In addition, missing data were obtained by the interpolation method.

The evaluation levels of sustainable development of WRB in Shaanxi Province rose from 1.29 in 2009 to 1.87 in 2018 with an upward overall trend and a subtle fluctuation (Figure 2 and Table 2). The inflection points were detected between 2013 and 2017, and the values remained around 1.6 from 2014 to 2016.

At the regional scale, the levels of sustainable development in different regions (Table 2 and Figure 3A). The level of sustainable development in Xi’an was much higher than that of the other four cities (Tongchuan, Baoji, Xianyang, and Weinan) from 2009 to 2018. It indicated that the levels of sustainable development of these four cities had different levels of hysteresis, and different regions showed diversified development. The value of Tongchuan was the lowest, hovering between 0.20 and 0.26. The levels of sustainable development in four cities except Tongchuan had seen a yearly increase.

The economic development system (B₁) and the social development system (B₂) were on a similar development track compared with the sustainable development system (A) (Figures 3B,C). In comparison, the value of the ecological development system (B₃) was far lower than that of the economic development system (B₁) and social development system (B₂) (Figure 3D), indicating the lag of ecological development behind local economic and social development. In the economic development system (B₁) and the social development system (B₂), the values of the four cities (Tongchuan, Baoji, Xianyang, and Weinan) were relatively centralized, with only the value of Xi’an being far ahead than that of the rest (Figure 3A). In the ecological development system (B₃), the increased values of Weinan in 2017 and Baoji in 2018 were 0.19 and 0.17, respectively, while the values of the other three cities (Xi’an, Tongchuan, and Xianyang) were relatively stable over the past decade. The level of sustainable development in the ecological system was the lowest, illustrating that the ecological development lagged behind economic and social development in WRB in Shaanxi Province and sustainable development was unbalanced.

Through the change of the spatial distribution for the sustainable development of WRB in Shaanxi Province (Figure 4) and calculation of the relative parameters of standard deviational ellipse (Table 3) from 2009 to 2018, the evolution of spatial pattern was analyzed from four aspects of spatial distribution (center, shape, range, and direction) to account for the dynamic changes of spatial difference.

The spatial distribution centers of sustainable development of WRB in Shaanxi Province were adjacent to Xi’an and Xianyang in 2009–2018. Overall, the spatial distribution center shifted to the north, showing that the accelerated growth speed of cities in the northern part of the axis, and the enhanced influence on the overall distribution pattern of the study area. The rotation angle of the standard deviational ellipse of spatial distribution dropped with a small counterclockwise rotation, suggesting that the study area in the northeastern cities were growing faster than the southwestern cities.

From the perspective of a spatial distribution shape, the long axis of the ellipse increased first and then shortened. Such a trend indicated that the spatial distribution shape changed from dispersion to polarization and then to dispersion. The changes in the short axis were the opposite. On the whole, the spatial distribution ellipse showed an obvious flattening trend; that is, the long axis grew and the short axis shrank. Afterward, the flattening trend gradually weakened and the directivity abated.

The obstacle degree of 31 indicators ranked by the obstacle degree model (Table 4 and Figure 5). The biggest obstacle degree was the number of college students per 10,000 (D₁₂). Prior to 2013, the financial revenue (D₂) and the amount of water resource per capita (D₂₁) were ranked second and third, respectively. The rankings were reversed from 2013 to 2017, indicating that the influence of economic obstacles on sustainable development of WRB in Shaanxi Province was gradually weakened with the increase of financial revenue. The fourth obstacle indicator was the investment in water conservancy as a percentage of GDP (D₃₀), while the fifth obstacle factors alternated between the gross domestic product (D₁) and urban living area per capita (D₁₆).

The ecological development of WRB in Shaanxi Province fell so far behind economic and social development on the whole during 2009–2018, despite the striking advancement of ecological development that had been made at the later stage of the study. The improvement of ecological development cannot be separated from the management behavior of the government. China attaches great importance to RBSD in the face of environmental degradation and water shortage. In 2014, President Xi Jinping called for a water control policy of “giving priority to saving water, balancing space, systematic treatment, and exerting force all-sided.” From 2016 to 2017, the Shaanxi provincial government issued a series of policies such as the Overall Plan for the Construction of Weihe Ecological Zone in Shaanxi Province and the Implement Plan Comprehensively of River Administrator in Shaanxi Province. Subsequently, a major national strategy of “Ecological conservation and high-quality development of the Yellow River basin” was proposed in 2019. WRB is a typical region with water shortage and underdeveloped economy, and water resources pose an obvious constraint on the sustainable development of WRB in Shaanxi Province. The water resources shortage and ecological environment pollution hamper the sustainable development of the economy and society. Conversely, the long-term development model has only focused on the aspects of economy and society, exerting great pressure on the ecological environment. Thus, solving the contradiction between economic and social development and environmental protection should be considered pivotal to the sustainable development of WRB in Shaanxi Province. The government departments must attach importance to the basin ecological management and water resources conservation for the sake of ensuring sustainable development of WRB in Shaanxi Province.

Among the five cities, Xi’an was identified as the region with the highest level of sustainable development during the study period, while Tongchuan was the lowest. Xi’an has developed into the only megacity in northwest China by virtue of its sound economic-social development foundation and the status as the central city of Shaanxi Province. Xi’an is in a high-speed state of sustainable development; its core leading role constantly enhanced, exerting a siphon effect. Meanwhile, Tongchuan, as a resource–based city in its early development stage, is facing the pressure of resource exhaustion, limited natural conditions, and prominent environmental problems, impeding its sustainable development. The results revealed evident polarization among regions as well as unsynchronized sustainable development. The study area belongs to an important exploitation area of Guanzhong Plain urban agglomeration, having formed a superior economic base in the long-term development. The western development provided favorable conditions for resource-rich regions, which is the main reason for the internal differences in sustainable development among regions. Besides, the implementation of the Belt and Road Initiative has greatly promoted regional coordination and sustainable development.

The results of obstacle degree unexpectedly discovered that the amount of water resource per capita (D₂₁) and the investment in water conservancy as a percentage to GDP (D₃₀) in the ecological development system (B₃) were vital factors hindering sustainable development of WRB in Shaanxi Province. The ecological environment, especially water resources, acts as a primary in the river basin sustainable development. Water conservancy construction is regarded as the basic support and important guarantee for promoting economic growth, social progress, and ecological control. In recent years, investment in water conservancy construction and water conservancy projects have seen a continuous increase, especially the construction of the Water Diversion from Hanjiang River to Weihe River basin project (172 major national water conservancy projects of China in 2015 and 10 major water ecological projects of Shaanxi Province in 2017), bringing obvious ecological–economic benefits.