Evaluating the effectiveness of the water-saving society construction in China: A quasi-natural experiment

Quantifying the mutual effects of water trading and systematic water saving in a water-scarce watershed of China

In this study, a conjunctive water management model based on interval stochastic bi-level programming method (CM-ISBP) is proposed for planning water trading program as well as quantifying mutual effects of water trading and systematic water saving. CM-ISBP incorporates water resources assessment with soil and water assessment tool (SWAT), systematic water-saving simulation combined with water trading, and interval stochastic bi-level programming (ISBP) within a general framework. Systematic water saving involves irrigation water-saving technologies (sprinkler irrigation, micro-irrigation, low-pressure pipe irrigation), enterprise water-saving potential and water-saving subsidy. The CM-ISBP is applied to a real case of a water-scarce watershed (i.e. Dagu River watershed, China). Mutual effects of water trading and water-saving activities are simulated with model establishment and quantified through mechanism analysis. The fate of saved water under the systematic water saving is also revealed. The coexistence of the two systems would increase system benefits by [11.89, 12.19]%, and increase the water use efficiency by [40.04, 40.46]%. Thus mechanism that couples water trading and water saving is optimal and recommended according to system performance.

Influence and mechanism of solids on the air pressure fluctuations on the building drainage system

The conventional building drainage system was constructed based on the theory of two-phase flow involving water and air. However, the drainage system contained a more intricate three-phase flow, encompassing water, air, and solids, which was relatively overlooked in research. This study addressed the impact of solids on pressure fluctuations, air flow rates, and hydraulic jump fullness within the drainage system, considering three factors: the mass factor, cross-section factor, and viscosity. The investigation was conducted within a single-stack system using both experimental methods and CFD simulations. The findings revealed a positive correlation between both positive and negative pressures and above three factors. The mass factor and the cross-section factor had a more significant impact on the negative pressure of the system. The maximum growth rates of negative pressure extremes under different mass and cross-section factors reached 7.72 and 16.52%, respectively. In contrast, the viscosity of fecal sludge had a slightly higher effect on the positive pressure fluctuation of the drainage system, with the maximum growth rate of positive pressure extremes at 3.41%.

Improving water efficiency is more effective in mitigating water stress than water transfer in Chinese cities

The interactions between human and natural systems and their effects have unforeseen results, particularly in the management of water resources. Using water stress mitigation as an example, a water resources management effect index (WRMEI) was created to quantitatively evaluate the trends of water management effects. This revealed that the WRMEI was decreasing due to the impact of the water resources management process. The findings demonstrate that water resources management has unintended effects: there was a gap between the expectation of water stress to be mitigated and the actual results of water stress increasing. That is caused by human activities in water utilization: (1) increasing available water resources from water transfer was not utilized sparingly in the receiving cities-increased water transfers from external sources increase domestic water consumption per capita; (2) improving water efficiency has a positive effect on mitigating water stress, but the population growth decreased the efficiency. It was concluded that much greater attention needs to be paid to water conservation in residential and living use to counter these unintended water management effects.

Water resource dynamics and protection strategies for inland lakes: A case study of Hongjiannao Lake

Globally, lakes are drying up and shrinking and inland lakes, in particular, face severe water shortage problems. Thus, the degradation mechanisms and protection measures for inland lakes urgently need to be explored. Hongjiannao Lake (HL), an inland lake on the border of Shaanxi Province and Inner Mongolia Autonomous Region of China, was selected for the present case study. The evolution of HL was analyzed and the current lake water storage was measured on site. The driving factors of water resource changes in HL were discussed based on meteorological and landcover data. The results showed that (1) from 1929 to 2021, the lake area of HL experienced four stages: formation, stability, shrinkage and recovery. The smallest water area was 31.08 km2 in 2015, half the size of lake in the 1960s. (2) Spatially, the morphological changes of HL mainly occurred where the rivers entered the lake. (3) In 2021, the average depth of HL was 3.77 m, and the water storage capacity was 140.56 million m3. (4) The annual average evaporation was 3.36 times the amount of the annual average precipitation in Hongjiannao Basin (HB), but climate change was not the main driver of changes in the HL area. (5) In the past 20 years, cultivated land and artificial surface increased by 3.11% and 1.04%, respectively, whereas grassland and water body decreased by 3.51% and 0.45%, respectively. The expansion of cultivated land and artificial surface, as well as the construction of reservoirs upstream of the lake, hindered the replenishment of water resources to HL. This study recommends a range of strategies for water resource protection in inland lakes, including implementing ecological restoration projects, carrying out inter-basin water transfer measures, improving the efficiency of regional water resource use, and improving industrial structure and distribution.

Does the South-to-North Water Diversion Project promote the growth of enterprises above designated size in the water-receiving areas?-Evidence from 31 provincial-level administrative regions in China

The South-to-North Water Diversion Project (SNWDP) is believed to drive the next phase of sustainable productivity growth, meeting growing water demand, so as to address increasing environmental sustainability challenges. The Middle Route of SNWDP is regarded as an extremely large long-distance inter-basin water diversion project, which has benefited Henan, Hebei, Tianjin and Beijing since 2014 with great sustainable changes to the cities, groundwater, ecological environment, industrial structure and social development of the beneficiary areas. Taking the number of industrial enterprises above designated size (IEDS) in the water-receiving areas as the research object, this paper takes the year of policy implementation 2014 as the basic time point, evaluating the change of the number of IEDS in the beneficiary areas of the Middle Route of SNWDP through difference-in-difference model. The results show that: (1) The Middle Route of SNWDP promotes the additional growth of the number of IEDS in the beneficiary areas. (2) When the Middle Route of SNWDP promotes the growth of the number of IEDS in beneficiary areas, there is no regional difference for regions with different development levels. (3) The reasons why the Middle Route of SNWDP contributes to the additional growth of the number of IEDS are composed of promoting mixed ownership reform of enterprises in beneficiary areas, increasing water supply and increasing population. However, the Middle Route of SNWDP has not had a significant impact on the traditional total factor productivity or the components of production factors, technology and capital. From the final outcome, the South-to-North Water Diversion Project has played a facilitating role in the sustainable development of large-scale enterprises in the water-receiving areas.

Exploring the drivers of quantity- and quality-related water scarcity due to trade for each province in China

Previous studies have explored virtual water flows due to interprovincial trade within China as well as related impacts on both regional quantity- and quality-related water scarcity aspects. However, the driving forces behind changes in these impacts remain unknown, especially the quality-related water scarcity. Exploring these driving forces can provide targeted measures to mitigate the negative impact of trade on these two types of water scarcity issues. In this study, blue and grey water footprints have been calculated under the consideration of interregional trade between provinces within China and those attributed to international exports from 2007 to 2015. This calculation was based on multi-regional input output model (MRIO). Moreover, the drivers of changes in blue and grey water footprints due to trade have been explored through structural decomposition analysis. The results showed that blue and grey water footprint increased and then slightly decreased from 2007 to 2015 in China. At the same time, interregional trade made an increasing contribution to the blue and grey water footprint, and the proportion increased from 28.8% to 35.0% and from 22.4% to 28.6%, respectively, from 2007 to 2015. The roles of importers and exporters regarding the blue and grey water footprint driven by interprovincial trade within China have changed little, and the quantity- and quality-related water scarcity issues of the main exporters have been intensified by interprovincial trade. A reduction in the water footprint intensity yielded the largest contribution to curb the increase in blue and grey water footprint driven by interprovincial trade. Our study showed that an improvement in efficiency of water use from both quantity and quality perspectives is the key to accomplish sustainable water use in China, especially considering the impact of trade on regional quantity- and quality-related water scarcity issues.

Income inequality, carbon emissions, and green development efficiency

Income inequality affects not only social well-being, health, and carbon emissions but also the strategy for green development in China. Based on the panel data of 205 cities in China from 2010 to 2020, a panel model with partial linear functional coefficient is used to analyze and test the relationship between income inequality, carbon emissions, and green development efficiency under different regional economic development levels. The empirical results show that the impact of income inequality on carbon emissions and green development efficiency is significant. The worsening of income inequality could aggravate carbon emissions, but the effect of income inequality on carbon emissions shows an increase-decrease-flattening with the continuous improvement of regional economic development. In terms of affecting the green development efficiency, the effect of income inequality on the efficiency of green development presents an inverted U shape. However, the number of cities where income inequality has an inhibitory effect on carbon emissions and green development efficiency has increased over time, and the impact of income inequality in a few cities on green development efficiency is not significant. These findings provide new insights into the understanding of shared prosperity and the strategy of carbon peaking and carbon neutralization in China.

Analysis of the Relationship between Economic Development and Water Resources-Ecological Management Capacity in China Based on Nighttime Lighting Data

Water resources are important factors limiting social and economic development, so how to ensure the coordination between economic development and water resources-ecological management capacity has become a key issue that needs to be addressed urgently for China's high-quality economic development. This paper used nighttime light data as proxy variables of economic development to calculate the coupling coordination degree between provincial economic development and water resources-ecological management capacity in China from 2004 to 2019 based on the coupling coordination degree model; w constructed a spatial econometric model to explore the spatial correlation and influencing factors between economic development and water resources-ecological management capacity. The results are shown in the following: (1) The overall level of China's economic development is on an upward trend, but the regional development is unbalanced, showing a decreasing spatial pattern distribution of the eastern coastal region-mid-western region-far-western region. (2) The level of water resources-ecological management capacity is low, and the spatial distribution shows a decreasing trend in the far west-central and western-eastern coastal regions. (3) The level of coupling and coordination between economic development and water resources-ecological management capacity rises from a mild imbalance level to a little imbalance level, and the spatial distribution is consistent with the spatial distribution of economic development. (4) The factors influencing the level of coupling and coordination of inter-provincial economic development and water resources-ecological management capacity in China mainly involve the population scale, technological progress, affluence, and foreign direct investment. Each province and city should take into account its own actual situation and develop targeted measures to promote the coordinated development of economic development and the water resources-ecological management capacity.

Blue sky defense in low-carbon pilot cities: A spatial spillover perspective of carbon emission efficiency

The improvement of carbon emission efficiency is crucial to the realization of the global carbon peaking and carbon neutrality goals. Based on the panel data of 282 cities from 2004 to 2018 in China, this paper employs the stochastic frontier analysis approach combined with the Sheppard distance function to calculate the total factor carbon emission efficiency of each city. Regarding the low-carbon pilot city policy as a quasi-natural experiment, we evaluate the impact of the pilot policy on carbon emission efficiency and its spatial spillover effect using the spatial difference-in-differences model. The results show that the pilot policy can significantly improve the carbon emission efficiency and has long-term dynamic effects. Also, the effect of the policy has spatial spillover, and has a positive impact on the neighboring cities. Mechanism analysis implies that optimal allocation of resources, energy conservation and green technology innovation make the low-carbon policy play an important intermediary role in promoting carbon emission efficiency. Besides, the effects of the pilot policy have obvious heterogeneity, especially cities in large, higher population densities and the north. These findings reveal that low-carbon pilot city policies are indispensable for both implementing the dual-carbon strategy and winning the defense for the blue sky.

Evaluating the water-saving and wastewater-reducing effects of water rights trading pilots: Evidence from a quasi-natural experiment

Water rights trading is a market mechanism that promotes the conservation, protection and optimal allocation of water resources. This paper takes the water rights trading pilots' policy as a quasi-natural experiment, and then adopts the spatial difference-in-differences model to investigate the water-saving and wastewater-reducing effects of water rights trading pilots by using the panel data of 30 provinces in China from 2006 to 2019. The results indicate that water rights trading has good environmental governance effects on water-saving and wastewater-reducing in the pilot areas. However, water rights transactions are mainly concentrated within provinces, and there is no spatial spillover effect. Besides, the pilot policy has more long-term dynamic effects in reducing sewage discharge than water-saving due to rebound effect possibly. The optimization of the industrial structure and environmental regulation play important roles in the realization of the policy effects of the water rights trading pilots. An important implication is that water rights trading pilots are worthy of promotion throughout China in view of the policy effects, and China should focus on inter-regional market transactions and industrial structure transformation to promote the optimization of the water rights trading mechanism.

A Comprehensive Post Evaluation of the Implementation of Water-Saving Measures in Xiangtan, Hunan Province, China

Water resource is an important foundation to support industrial and agricultural production, in the maintenance of national energy security role is irreplaceable. Water conservation and the effective use of water resources are essential for achieving sustainable development in China. The construction of water-saving society is a prerequisite for realizing efficient utilization of water resources and an important strategic development for moving towards environment-friendly society. This study established an index system to evaluate the implementation of water-saving measures in Xiangtan, Hunan province, China. The index system incorporated five aspects: (1) comprehensiveness; (2) agricultural water; (3) industrial water; (4) domestic water, and; (5) aquatic ecology and environmental management. Analytic hierarchy (AH) was used to determine the weights of indices, and AH was integrated with grey relative analysis to establish a comprehensive system for the evaluation of the water-saving measures in Xiangtan. The results showed that the implementation of water-saving measures in Xiangtan is generally progressing well. However, industrial added value water consumption per 10,000-yuan remains at the primary stage and wastewater reuse remains limited. In addition, water use per 10,000-yuan gross domestic product, the coverage of water-saving irrigation projects, industrial wastewater reuse, and the leakage rate of urban water supply network remain at an intermediate stage. The result of this study can scientifically reflect the level of the water-saving measures in place in Xiangtan and could guide future implementation of water saving measures in Xiangtan and in other cities.

Agricultural Water Utilization Efficiency in China: Evaluation, Spatial Differences, and Related Factors

Agricultural water utilization efficiency (AWUE) reflects the rational utilization of water resources in agricultural production. Improving AWUE is important for both improving the levels of agricultural production and reducing consumption of water resources, and it is significant to explore the spatial differences between different cities and regions and the various factors related to AWUE, both theoretically and practically. The AWUE of totally 281 cities at the prefecture level or above in China between 2003 and 2018 was evaluated using the super-efficiency slacks-based measure (SBM). The spatial differences in AWUE were simulated by exploratory spatial data analysis (ESDA), and the various factors affecting AWUE were simulated using the graphical statistical tool, Geodetector. The results of this study are as follows: (1) The mean value of AWUE across the country was merely 0.23 when it registered a record high in 2018, indicating that the AWUE in China was low; (2) AWUE showed significant spatial differences judging from the results of ESDA, and the low-low type was the principal spatial type, which was distributed mainly in the North China Plain and the Loess Plateau; and (3) agricultural technology was the main factor affecting AWUE.

Dynamic simulation for comprehensive water resources policies to improve water-use efficiency in coastal city

Coastal cities play an important role in regional economic development and sustainable development strategies of water resources and their ecological environment. As a typical coastal city in Hebei Province, Qinhuangdao city is facing severe problems, such as water shortages and water environment deterioration, while social and economic development continues. Based on input-output analysis, we established a dynamic optimization model among Qinhuangdao city's socioeconomic development, water resources and water environment. The 2013-2030 simulation after introducing comprehensive water resources policies of regional development, examines the regional socioeconomic development, optimizes the water resources supply structure and improves the water environment under the optimal scenario, and evaluates policy feasibility through cost-benefit analysis (CBA). The simulation results suggest that under the optimal scenario, the water-use efficiency (WE) of Qinhuangdao is improved by 59.14% and the proportion of reclaimed water and desalinated seawater in the water supply structure is increased by 13.70%. In addition, it has achieved an average annual gross regional production (GRP) growth rate of 6.36% and an average annual chemical oxygen demand (COD) emission rate of 17.95%. Moreover, the net present value (NPV) of the projects under the optimal scenario is 1.534 billion Chinese yuan (CNY), which means that the policy is economically feasible. Our research is helpful to improve the WE, optimize the water supply structure and protect the hydrogeological environment in coastal cities with water shortages and can provide a reference for Qinhuangdao city and other similar coastal cities to realize the rational utilization of water resources and regional sustainable development.