| Water resources were the basis for human survival,and water security was related to the sustainability of the development of the whole human society;Agricultural water security ba-sically determined the state of water security,and the global agricultural water consumption accounted for about 70%of the total water consumption.In China,agriculture in irrigation district was the ballast stone to ensure food security,bearing more than 75%of food production;Water security in irrigation district was the key prerequisite to ensure food security in China,and agricultural water consumption in irrigation district accounted for more than 50%of the total water consumption.Currently,there was limited research on water security diagnostic sys-tem on the scale of irrigation district.In the context of the country’s explicit requirement to ensure water security,food security and construction of high quality irrigation district,the study of water security in irrigation district not only clarified the complex correlation mechanism between current food security,water security and rural revitalization,but also had a very im-portant strategic value for the long-term guarantee of China’s food security and national security,and provided an example for water security studies in the same type of irrigation district.In this study,based on the concept of system security and sustainable development,the theory of water security at the irrigation district scale was elaborated with system functional security and high quality development as the core,and a diagnosis and optimal control system was constructed by the above theory,including the diagnosis model,diagnosis index,Set Pair-Matter Element coupling model(SPME)and optimal control and risk prediction model oriented to the diagnosis results.On the basis of the above,the evolution characteristics of water security elements were identified in Jinghuiqu Irrigation District,and the current situation of water se-curity was initially grasped;The water security problems were diagnosed in Jinghuiqu Irriga-tion District,and the synergistic evolution of water security elements,the key risk factors af-fecting the system functional security and the constraints of high quality coordinated develop-ment were clarified;The optimal regulation and risk prediction model of water security suita-bility was established,and optimal solutions were proposed.The main conclusions obtained were as follows:(1)Based on the system and sustainable development view,the connotation and exten-sion of water security in irrigation district was tried to expand.The connotation was to ensure the functional security and high quality development of the irrigation system,to realize the unified management of water quantity and quality and the sustainable use of water resources;Through the connotation of water security in irrigation district,the composition of its extension included food security,economic security,social security,ecological security and national se-curity.(2)Based on the theory of water security system in irrigation district,the diagnosis model and index system of water security in irrigation district were constructed under the dual perspective of system functional security and high quality development;Using D-S evidence and Nash equilibrium theory method,the diagnosis indexes were selected and assigned with combination weights respectively;By the mapping relationship between same-different-oppo-site principle of Set-Pair and the topizable domain of Matter Element,SPME coupling model with uncertainty and incompatibility was established.(3)Using trend analysis,mathematical statistics or other methods to identify and ana-lyze the water security elements in Jinghuiqu Irrigation District,the results showed that:the climate would be in a relative drought period in the current and future period,and the amount of groundwater resources and surface water resources showed a decreasing trend,while along with the accelerated urbanization process,the farming district decreased by 36.9%from 1990to 2020,and the food production decreased by 18.4%from 2010 to 2020.On this basis,a com-prehensive diagnostic analysis of water security using the above diagnostic system was exe-cuted,and the results showed that:along with the synergistic evolution of water security ele-ments,water resources elements played a dominant role in the development of system func-tional security,among which over-exploitation of groundwater,decline in surface water and decline in the proportion of grain crops cultivated had become key risk factors impeding the functional security,with a particular serious in Gaoling and Jingyang counties;At the same time,the shortage of water resources and the imbalance of the canal-well irrigation ratio had hindered the coordination of high quality development,most prominently in Gaoling and Jingyang counties;The water security in Jinghuiqu Irrigation District was in the"primary security"state,which was consistent with the actual situation,and compared with the evaluation of the Set Pair and Matter Element,the SPME coupled model had shown some superiority in terms of stability,effectiveness and applicability.(4)By coupling the numerical model of water resources system and multi-objective op-timization model,a four-dimensional optimization regulation model was constructed,contain-ing social benefit,economic benefit,ecological benefit and fairness of water use.The regulation results showed that:In dry year,the optimal solution of well irrigation was 149 million m~3 with canal irrigation of 194 million m~3,and the appropriate proportion of winter wheat planting was about 0.60,with a 18%increase in the comprehensive benefit target;In normal year,the optimal solution of well irrigation was 144 million m~3 with canal irrigation of 235 million m~3,and the appropriate proportion of winter wheat planting was about 0.50,with a 14%increase in the comprehensive benefit target;In high flow year,in order to ensure groundwater conservation,the well irrigation volume should be controlled at 0.8-0.9 billion m~3,the canal irrigation volume should be kept at 172 million m~3,and the appropriate proportion of winter wheat planting should be about 0.47,with a 10%increase in the comprehensive benefit target.In addition,the well irrigation volume of Jingyang county with serious groundwater overdraft,needed to be con-trolled at 0.36-0.39 billion m~3 in dry year,0.28-0.30 billion m~3 in normal year,0.19-0.21 billion m~3 in high flow year.(5)Using the cloud-Markov prediction model based on random numbers to predict and analyze the evolution trend of water security risk in Jinghuiqu Irrigation District before and after optimal regulation,the results showed that:Under the current conditions,water security presented the coexistence characteristics of medium-high risk,medium risk and medium-low risk in 2020-2030,with the occurrence probability of 0.27,0.36,0.30,and medium risk occu-pied dominant position;After optimization,the system functional security,the level of high quality development and the comprehensive water security had increased by 3.7%,4.4%and4.1%respectively,and the system functional security transformed from"primary security"to"relatively safe".In 2030,the probability of medium-high risk,medium risk and medium-low risk of water security was 0.21,0.32 and 0.37 respectively,and the confidence probability of medium-low risk would be increased to 0.61 in 2051,reaching the level of fully reliable con-clusion.By optimizing the regulation mechanism,the water security situation in Jinghuiqu Ir-rigation District would be significantly improved in the current and future period,and the opti-mized scheme can provide long-term guarantee for water security in the irrigation district. |
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