Reliability-resilience-vulnerability Of Water Supply System And Its Response Relationship To Multiple Factors

China has more people and less water,and the distribution of water resources is uneven in time and space.The sustainable development of social economy is restricted by regional drought and water shortage.In addition,driven by climate change and human activities,extreme drought events tend to be more and stronger,and the contradiction between supply and demand becomes more prominent.The frequency,severity and the duration of water shortage events have aroused wide concern,however,the traditional water supply reliability index(reliability)only reflects the failure frequency,which cannot fully reflect the socio-economic impact of extreme water scarcity events.Hence,represent the system attributes completely.With the diversification of water supply security measures and the gradual improvement of evaluation standards,the water supply system presents the characteristics of "multi-elements and multiattributes".An in-depth understanding of the multi-element-multi-attribute correlation of water supply system can help decision makers to choose the most reasonable and economical water supply guarantee measures,which is an important basis for system planning and design,operation and management,and also a key scientific problem to be solved urgently.Therefore,this paper focuses on the correlation between the reliability,resilience,vulnerability and multiple factors of the water supply system,and focuses on the analysis of:(1)The influence mechanism of inflow,demand and storage capacity on different system attributes,(2)competition and collaboration between multiple attributes under different scheduling strategies,(3)the response mechanism between different water supply objects and multiple elements of the system.The main achievements are as follows:(1)This paper comprehensively analyzed the understanding and definition of system reliability,resilience and vulnerability of different researchers,and proposed the multi-attribute system of water supply system.In order to make water supply systems in different regions comparable,four dimensionless variables,namely annual runoff variation coefficient CV,water demand rate YI,reservoir capacity coefficient ? and standard net inflow m,were used to characterize the inflow,water demand and storage capacity of the system.A standardized,dimensionless multi-element system of water supply system was proposed.Within the reasonable variation range of multiple factors,a large number of experimental samples were generated by using random sampling technology,and the experimental samples were divided into 4 categories to represent different types of water supply systems,which laid a foundation for the analysis of multi-factor-multi-attribute correlation of the system.(2)The influence degree of multiple factors on reliability,resilience and vulnerability of water supply system is analyzed quantitatively by using multiple elastic regression analysis method,and the controlling factors in different types of water supply system are explored.The results show that in different types of systems,the annual runoff variation coefficient CV,water demand rate YI and storage capacity coefficient ? have obvious diminishing marginal benefit to improve the system reliability.For the water supply system in different regions,it is necessary to identify the weak links among the multiple elements,and then to select various water supply guarantee measures,such as inter-basin water transfer,water-saving management and reservoir construction.For the two attributes of resilience and vulnerability,no matter what type of water supply system,the annual runoff variation coefficient CVhas the greatest influence degree,followed by the water demand rate YI,and the reservoir capacity coefficient ? has the least influence degree.It is difficult to improve the resilience and vulnerability of the system by increasing the reservoir capacity,and the measures such as inter-basin water transfer and standby water source construction have the best effect on the improvement of these two attributes.(3)From the perspective of operation management,the effects of reservoir hedging regulation on system reliability,resilience and vulnerability,as well as the competition and coordination among three kinds of attributes are revealed.The results show that with the increase of "hedging degree",the reliability and vulnerability of the system become worse,while the resilience tends to be better first and then worse,and the implementation of hedging rules makes reservoir operation a complex multi-objective problem.In the multi-objective nondominant solution space,the critical region where the competition-collaboration relationship between multiple attributes is transformed is identified.When the "hedging degree" is high,the system resilience and reliability show a cooperative relationship,and the system vulnerability shows a competitive relationship.When the "degree of hedging" is low,the relationship between the resilience of the system and the other two types of attributes is reversed.At the same time,the consistency of the above rules is confirmed based on a number of cases,and the application conditions of the reservoir hedge rule are analyzed,that is,when the standard net inflow m is large enough,the SOP rule can make all kinds of attributes reach a satisfactory state,while the hedge rule will cause unnecessary restrictions on the water supply.When the standard net inflow m is too small,the water supply guarantee rate cannot meet the basic requirements,and the hedging rules will further reduce the water supply guarantee rate.(4)The responses of GSI of urban,agricultural and ecological water supply subjects to the changes of multiple factors,such as water demand rate YI,annual runoff variation coefficient CV,storage capacity coefficient ?,water supply priority,water use ratio,and scheduling rule,were quantitatively analyzed by ANOVA.The results show that when there are multiple types of water supply objects,the direct use of reliability,resilience and vulnerability attributes will cause the evaluation system to be too complex.GSI can comprehensively reflect the influence of the three types of attributes.The value of determines the degree of GSI's inclination to different attributes.When 1.5<<2.0,GSI can better weigh the three types of attributes.GSI of urban,agricultural and ecological water supply objects is significantly correlated with water demand rate and annual runoff variation coefficient.In addition,urban water supply objects are very little affected by other factors.The object of agricultural water supply is greatly affected by the hedging regulation.The water shortage degree of ecological water supply objects is closely related to water supply priority,and the water competition between ecological water supply and other two types of water users is mainly caused by water supply priority.