Water Resources Allocation And Ecological Environment Evaluation Of Shanxi Water Receiving Area Of Guxian Water Control Project Of Yellow River

In view of the fact that the contradiction between supply and demand of water resources in Shaanxi receiving area of the Yellow River Guxian Water Control Project is prominent and the ecological water use is not guaranteed,the technical route of field investigation,theoretical analysis and numerical calculation is used to carry out the research on the influence of Guxian Water Control Project on the optimal allocation of water resources and ecological environment in Shaanxi receiving area,and the agricultural planting structure in the receiving area is optimized and adjusted,which provides theoretical guidance and technical support for regional water resources layout,ecological environment protection and sustainable development of national economy.The main research contents are as follows:(1)Based on the actual situation of the water receiving area in the current year(2019),the time series method is used to predict the national economic development index an d water supply in the planning year(2030),and the quota method is used to predict the water demand.The results show that with the growth of economy and society,the demand for water resources in the water receiving area has increased significantly,the water supply has decreased with the loss of water conservancy projects and the limited exploitation of groundwater,and the contradiction between supply and demand of water resources has further intensified.Under the guarantee rate of 50%and 75%,the water shortage in the water receiving area in 2030 is 1.355 billion m3 and 2.165 billion m3 respectively,and the water shortage rate is 46.28%and 59.87%respectively.(2)Based on the non-dominated sorting genetic algorithm(NSGA-Ⅲ)with reference point selection,a multi-objective optimal allocation model of water resources is constructed with the goal of maximizing economic benefits,minimizing water shortage and minimizing chemical oxygen demand(COD)emissions.Combined with TOPSIS decision theory,the water resources allocation schemes before and after the West Route of the South-to-North Water Diversion Project after the construction of the Guxian Water Conservancy Project of the Yellow River and under different precipitation frequencies are proposed.The results show that under the precipitation frequency of P=50%,the total water allocation before and after the entry into force of the western route of the South-to-North Water Diversion Project after the construction of the Guxian Water Control Project is 2.603 billion m3 and 3.298 billion m3 respectively,and the water shortage rate is reduced to 35.15%and 46.28%respectively.Under the precipitation frequency of 75%,the total allocated water volume before and after the entry into force of the western route of the South-to-North Water Diversion Project after the construction of the Guxian Water Control Project was 2.482 billion m3 and 3.175 billion m3,respectively,and the water shortage rate decreased to 28.52%and 47.68%,respectively.(3)Based on the economic-social-ecological comprehensive system,the ecological environment impact assessment model was constructed by using the analytic hierarchy process combined with the fuzzy comprehensive evaluation method,and the coordination degree of water resources and ecological environment in Shaanxi water receiving area was evaluated.The results show that with the continuous improvement of the water diversion project,the coordination degree of water resources and ecological environment in the water receiving area is increasing.(4)Aiming at the situation that the water shortage department is mainly planting industry after water resources optimization,a planting structure optimization model with the minimum water consumption and the maximum economic benefit is constructed.The non-dominated sorting genetic algorithm NSGA-II based on crowding degree selection is used to solve the problem.The crop planting structure in the water receiving area under different precipitation frequencies was optimized.Compared with before optimization,under P=50%precipitation frequency,the net output value increased by 1.629 billion yuan,and the water demand of planting industry decreased by 37.04 million m3.Under P=75%precipitation frequency,the net output value increased by 1.567 billion yuan,and the water demand of planting industry decreased by 47.79 million m3.It can be seen that the optimization of agricultural planting structure is of great help to the improvement of agricultural output value and irrigation water saving in the future.