Study On Optimal Allocation And Emergency Support Of Urban Multi-source Combined Water Supply

In recent years,the contradiction between supply and demand of water resources has become increasingly acute,which has promoted the rapid development of the new pattern of multi-source water supply,resulting in an increasingly complex urban water supply system.How to improve the utilization rate of urban multi-source water supply resources and the emergency protection of multi-source water supply systems Capacity has become a key issue that needs to be solved urgently.Starting from the purpose of efficient utilization of water resources,aiming at the particularity of the new pattern of multi-source water supply in the study area,and based on the theory of optimal allocation of water resources,this paper conducts research on the optimal allocation of water resources for the pattern of multi-source water supply in the study area,and at the same time aims at its new pattern,analyze the water supply risks of water sources,and carry out emergency water supply guarantee research on target areas.This paper chooses the urban-rural east line water supply project in Ningxia metropolitan area and its water supply scope as a case study.The main research contents and results are as follows:(1)Based on the investigation of hydrogeology,water resources and the east route water supply project of the study area,the population development forecast of the study area in 2025(near term)and 2035(long term)was carried out based on BP neural network.At the same time,based on the prediction of the economic and social development and the development of animal husbandry in the study area,the water demand of different water users in different regions of the study area and the water supply of water sources in the predicted level years of the study area were predicted and analyzed.The results show that in 2025(near term),the total water demand of the study area is 93.0695 million m~3,and the total available amount is 115.8677million m~3;in 2035(long term),the total water demand is 140.9427 million m~3,and the total available amount is 180.0658 million m~3,which lays the foundation for the subsequent research on optimal allocation of water resources and emergency support.(2)Based on the theory and principle of optimal allocation of water resources,a multi-objective optimization mathematical model including water resources objectives,economic objectives and environmental objectives was established on the basis of the prediction results of water supply and demand.Constraint conditions and model parameters were determined.NSGA-Ⅱ was used to solve the model and analyze the correlation between multi-objectives and the strength of the relationship.The results show that there is a negative correlation between water resources and economic goals and between economic goals and environmental goals,while there is a positive correlation between water resources and environmental goals.In 2025(near term),the relationship between water resources and economic goals is the highest,followed by the relationship between economic goals and environmental goals,and the relationship between water resources and environmental goals is the weakest.In 2035(long-term),the relationship between economic and environmental targets is strongest,followed by water resources and economic targets,and the relationship between water resources and environmental targets is weakest.(3)The weight of water resource objective,economic objective and environmental objective is determined by binary fuzzy comparison method as 0.48,0.32 and 0.20 respectively.The multi-objective fuzzy optimization model is used to screen the Pareto solution set obtained by the algorithm,and the maximum relative optimal degree u_i is selected as the optimal scheme:Under the optimal plan in 2025(near term),the groundwater consumption is 13.8628 million m~3,the secondary water consumption is 6.5167 million m~3,the surface water consumption is68.8172 million m~3,the economic target is RMB 42.885 billion,and the environmental target is 1.6191 million kg.Under the optimal plan in 2035(long-term),the target function value of groundwater consumption is 4.2883 million m~3,surface water consumption is 122.8143 million m~3,secondary water consumption is 10.3134 m~3,the economic target is RMB 70.10 billion,and the environmental target is 2.3303 million kg.(4)Through relevant planning standards and literature research,combined with the characteristics of economic society and water source of the study area,the emergency risk period of the study area was determined to be 7 days,15 days,30 days and 60 days,the water supply compression ratio of each industry was determined and the emergency water demand was calculated.According to the emergency water supply process,the emergency water supply scheme is determined in the study area,the results show that in 2025(near term),water supply accident occurs in the groundwater source area of Hedong area of Qingtongxia City,and the emergency water quantity cannot be met when the risk period is 7 days and 15 days.In 2035(long term),if the risk period is 60 days or more due to a major disaster at the Yellow River intake port,the emergency water supply in Litong District of Wuzhong City and Lingwu City will not be able to meet the emergency demand.It is suggested to increase the compression ratio of each water user or replan new emergency backup water source to meet the emergency water supply demand,to maintain the social stability of the study area and promote the coordinated and sustainable economic development of the study area.(5)According to the calculation of economic profit and loss of emergency water supply,under scenario 2,in 2025(near term),the economic profit and loss of Hedong area of Qingtongxia City is greater than RMB 0.006 billion and RMB 0.022 billion,respectively,because the emergency water supply does not meet the demand during the 7-day and 15-day risk periods.In scenario 1,in 2035(long term),the economic profit and loss of Litong District of Wuzhong City and Lingwu City will be more than RMB 3.703 billion and RMB 1.337 billion,respectively,due to the emergency water supply not meeting the water demand during the 60-day risk period.