Study On Spatial Equilibrium Evaluation And Regulation Of Water Resources In Large-scale Irrigation Area

The spatial equilibrium evaluation and regulation of regional water resources is the important technical basis and scientific management method with development and utilization of water resources are coordinated with economic and ecological environment development.The water demand and water supply respectively are comprehensive indicators of natural resource conditions and economic and social activities on water resources,the balance relationship between them can directly reveal the unit supply-demand equilibrium degree and spatial equilibrium degree of water resources system.In view of the increasingly prominent contradiction between supply and demand of water resources,this paper proposes a method for evaluating the spatial equilibrium degree of regional water resources based on the relationship between water supply-demand and seven-element connection number,and an evaluation and regulation study is carried out in the water resources system of large irrigation area:Firstly,the water resource system supply-demand equilibrium degree of each unit(county or city)was defined and calculated by the ratio of supply and demand difference to total supply and demand.Then,a comprehensive evaluation method based on the seven-element connection number is constructed,and the evaluation and comparative analysis of the spatial equilibrium degree of water resources system with and without water resources configuration within the system are carried out.Then,forecast the water demand and water supply in the long-term planning year(2035).On this basis,the evaluation and calculation of the unit equilibrium degree of water resources in each county(city)and the overall water resource spatial equilibrium grade of water resources system of irrigation area are carried out in 2035.Finally,the optimal regulation scheme to improve the spatial equilibrium of water resources in irrigation area are put forward.Main results obtained as follows:(1)The spatial equilibrium grade of water resources in Pihe irrigation district is evaluated by using the method proposed in this paper.In the current level year,when there is no water resources allocation within the system,the overall water resources spatial equilibrium level of the irrigation area is 2.95,which is in the state of moderate water shortage imbalance.After the allocation of water resources in the irrigation area,the spatial equilibrium grade of water resources in the irrigation area is increased to3.21,which means the disequilibrium of light water shortage.Using genetic algorithm to optimize the regional water resources allocation scheme,the water allocation ratios of Hefei City,Feidong,Feixi,Changfeng,Lu’an City and Shouxian county are 54.84%,0.69%,3.77%,7.28%,30.32% and 3.1% respectively,and the spatial equilibrium grade of Pihe irrigation area is improved to 3.42.(2)Under the scenario of average inflow in the long-term planning year,when there is no water resources allocation within the system,the overall water resources spatial equilibrium grade of the irrigation area is 2.75,that is,moderate water shortage disequilibrium.According to the current water resources allocation scheme,the spatial equilibrium grade of water resources in the irrigation area was increased to 3.08.Considering the external water diversion and using genetic algorithm to optimize the regional water resources allocation scheme,the water allocation ratios of Hefei City,Feidong,Feixi,Changfeng,Lu’an City and Shouxian are 33.52%,2.36%,9.64%,12.00%,22.31% and 20.17% respectively,and the spatial equilibrium grade of Pihe irrigation District is increased to 3.79,which means that the water supply and demand are balanced.(3)Under the scenario of 80% inflow frequency in the long-term planning year,when there is no water resources allocation within the system,the overall water resources spatial equilibrium grade of the irrigation area is 2.57,that is,moderate water shortage disequilibrium.According to the current water resources allocation scheme,the spatial equilibrium grade of water resources in the irrigation area is increased to 2.62.Considering the water diversion from external sources and using genetic algorithm to optimize the regional water resources allocation scheme,the water allocation ratios of Hefei City,Feidong,Feixi,Changfeng,Lu’an City and Shouxian county are 35.67%,3.71%,30.98%,2.46%,11.95% and 15.23% respectively,and the spatial equilibrium grade of Pihe irrigation district is increased to 3.51,which means slight water shortage disequilibrium.This study shows that: The evaluate method of supply-demand equilibrium degree of water resources can simultaneously express the disequilibrium of regional water shortage and excess water,so it can be widely applied to various situations;The improved seven-element connection number evaluation model can describe the uncertainty of complex water resources system in more detail,and provide a new way to accurately identify the spatial equilibrium state of regional water resources system;Due to the difference of the condition of natural and economic society,the equilibrium degree of water resources of different counties and cities are obviously different which in a same large irrigation area.Through the optimal allocation of water resources among units which in the system and the allocation of multiple external water sources,it can effectively improve the spatial equilibrium degree,which plays an important role in promoting the coordinated development of water resources and economic society and ensuring the smooth implementation of regional long-term planning.