Assessing the ecological security of the Three Gorges reservoir complex ecosystem based on the improved three-dimensional emergy ecological footprint model.

The ecological security (ES) of the reservoir complex ecosystem (RCE) is one of the critical components of watershed water security and sustainable development. Hence, accurately assessing the ES of the RCE is of utmost importance. This study proposed a novel ecological security assessment model based on the improved three-dimensional emergy ecological footprint (ESM-IEEF3D), which integrated various emergy flows during the RCE's construction and operation into a three-dimensional emergy ecological footprint (EEF3D) calculation account. The Three Gorges Project (TGP) is selected as a case study to evaluate the ES from 1993 to 2022 comprehensively. The results showed that the Three Gorges RCE mainly showed an ecological remainder state, and the inflow runoff enormously promoted the TGP's sustainability. The EEF3D indicated a fluctuation decrease trend with a mean value of 7.18 × 102 ha, illustrating that TGP's ecological security and sustainability levels are gradually improving. Regarding the ES evaluation indicators, the TGP's resource dependency and ecological pressure on the natural ecosystem and the external socio-economic system are steadily relieved. Furthermore, the Three Gorges RCE's resource utilization condition is safe, the structural characteristics are healthy, and the eco-economic coordination degree is continuously enlightening. Finally, applicable policy implications for improving the ecological security of Three Gorges RCE were provided. This study helps to understand the complex relationship between humans and ecosystems. It provides a novel framework to be used as an evaluation index and policy insights for hydropower ecological security and sustainable development.

Emergy-based sustainability evaluation model of hydropower megaproject incorporating the social-economic-ecological losses.

The sustainable development of the hydropower megaproject (HM) is one of the critical components of sustainable water resources management. Hence, an accurate assessment of the impacts of social-economic-ecological losses (SEEL) on the sustainability of the HM system is of utmost importance. This study proposes an emergy-based sustainability evaluation model incorporating the social-economic-ecological losses (ESM-SEEL), which integrated the inputs and outputs during HM's construction and operation into an emergy calculation account. The Three Gorges Project (TGP) on the Yangtze River is selected as a case study to comprehensively evaluate the HM's sustainability from 1993 to 2020. Subsequently, the emergy-based indicators of TGP are compared with several hydropower projects in China and worldwide to analyze the multi-impacts of hydropower development. The results showed that the river chemical potential (2.35 E+24sej) and the emergy losses (L) (1.39 E+24sej) are the primary emergy inflow sections (U) of the TGP system, accounting for 51.1% and 30.4% of the U, respectively. The flood control function of the TGP produced tremendous socio-economic benefits (1.24 E+24sej), accounting for 37.8% of the total emergy yield. The resettlement and compensation, water pollution during operation, fish biodiversity loss, and sediment deposition are the main L of the TGP, accounting for 77.8%, 8.4%, 5.6%, and 2.6%, respectively. Based on the enhanced emergy-based indicators, the assessment reveals that the sustainability level of the TGP falls in the middle range compared to other hydropower projects. Thus, along with maximizing the benefits of the HM system, it is necessary to minimize the SEEL of the HM system, which is a critical approach to promote the coordinated development of the hydropower and ecological environment in the Yangtze River basin. This study helps to understand the complex relationship between human and water systems and provides a novel framework that can be used as an evaluation index and insights for hydropower sustainability assessment.

Coupling coordination and spatiotemporal dynamic evolution of the water-energy-food-land (WEFL) nexus in the Yangtze River Economic Belt, China.

The interrelationship between regional water, energy, food, and land systems is extremely complex. Hence, accurately assessing the coupling coordination relationship and identifying the influential factors of the water-energy-food-land nexus (WEFL nexus) are of utmost importance. This study proposes a novel analytical framework and evaluation index system for exploring interactions across the WEFL nexus. The comprehensive benefit evaluation index (CBEI), coupling coordination degree (CCD) model, and obstacle factor diagnosis model are integrated to assess and analyze the coupling coordination relationship and spatiotemporal dynamic evolution of the WEFL nexus in the Yangtze River Economic Belt (YREB) from 2006 to 2020. The results indicated that (1) the CBEI and CCD generally increased from 0.23 to 0.79 and 0.45 to 0.88, respectively, revealing the upward trend of the coordination development levels of the WEFL nexus in the YREB. (2) The lower reaches achieved a relatively higher coordination development degree than the upper and middle reaches of the YREB. (3) The findings of obstacle factors reveal that agricultural non-point source pollution control, waterlogging disaster prevention, industrial solid waste efficient treatment, and urban water-saving are the essential fields that need to be improved in YREB's future development. This study helps to understand the complex interrelation of the WEFL nexus at different spatial-temporal scales and provides a novel framework that can be used as an evaluation system and policy insights for a region's integrated resources, environmental management, and green sustainable development.

Spatial multicriteria decision analysis of flood risks in aging-dam management in China: a framework and case study.

Approximately 30,000 dams in China are aging and are considered to be high-level risks. Developing a framework for analyzing spatial multicriteria flood risk is crucial to ranking management scenarios for these dams, especially in densely populated areas. Based on the theories of spatial multicriteria decision analysis, this report generalizes a framework consisting of scenario definition, problem structuring, criteria construction, spatial quantification of criteria, criteria weighting, decision rules, sensitivity analyses, and scenario appraisal. The framework is presented in detail by using a case study to rank dam rehabilitation, decommissioning and existing-condition scenarios. The results show that there was a serious inundation, and that a dam rehabilitation scenario could reduce the multicriteria flood risk by 0.25 in the most affected areas; this indicates a mean risk decrease of less than 23%. Although increased risk (<0.20) was found for some residential and commercial buildings, if the dam were to be decommissioned, the mean risk would not be greater than the current existing risk, indicating that the dam rehabilitation scenario had a higher rank for decreasing the flood risk than the decommissioning scenario, but that dam rehabilitation alone might be of little help in abating flood risk. With adjustments and improvement to the specific methods (according to the circumstances and available data) this framework may be applied to other sites.