Study On Optimal Allocation Of Water Resources In Tongliao City Based On Water Ecological Security

Water ecological security is an important part of national water security,and water resources are an important basis for water ecological security.With the rapid development of economy,society and urbanization,the balance between water resources system-economic and society system-ecological environment system has been gradually broken,problems such as shortage of water resources,water ecological damage,and water environment pollution have become prominent,and the contradiction between supply and demand of water resources has become more and more prominent.Tongliao City is located in an ecologically fragile zone in the arid and semi-arid agricultural and animal husbandry interlaced area.It is an important national commodity grain base and animal husbandry production base.Under the influence of water resource shortage and human activities,water ecological problems such as water resources development over-exploitation,groundwater over-exploitation,river flow interruption,reservoir drying,lake wetland shrinkage and grassland desertification followed one after another,and the risks of water ecological security are increasing day by day.The contradiction between water resources shortage and increased demand for water has become the main constraint of Tongliao City’s unbalanced and uncoordinated development.Therefore,carrying out research on the optimal allocation of water resources in Tongliao City based on water ecological security is of great significance for optimizing the water resources allocation pattern in Tongliao City,promoting water ecological governance and protection,ensuring water ecological security of Tongliao City,and promoting high-quality economic and social development.The main research contents and results are as follows.(1)Based on a long series of meteorological and hydrological data from 1956 to2016,this study analyzes the evolution characteristics of water resources elements such as precipitation,measured runoff,water resources and groundwater dynamics in Tongliao City in the past 60 years,and diagnoses the existing water ecological environment problems.The results show that the precipitation,measured runoff at representative hydrological stations,surface water resources,groundwater resources,and total water resources in Tongliao City in the past 60 years have all shown a decreasing trend.The variation points of the annual measured runoff series mainly occurred in the 1960 s and 1990 s.The groundwater recharge structure gradually evolved from the "natural" recharge mode in the natural state to the "natural-artificial" composite recharge model,and the groundwater discharge structure evolved from natural discharge to artificial discharge.The imbalance between replenishment and discharge has become more and more serious,and the loss of groundwater storage has continued to increase,resulting in a large-scale drop in groundwater levels.Climatic factors,changes in hydrological regimes and human activities have directly or indirectly led to a series of water ecological environment problems in Tongliao City,such as excessive development and utilization of water resources,serious overexploitation of groundwater,aggravation of river interruptions,reservoirs without water to store,and serious desertification of grasslands.(2)This study expounds the conceptual connotation of water ecological security,and determines the main characteristic values of water ecological security in Tongliao City according to the current situation of water resources and water ecological safety issues in Tongliao City.Water ecological safety covers the four-dimensional elements of water quantity,water quality,water area and water flow.According to the actual situation of Tongliao City,from the perspective of recovering the ecological environment of rivers and lakes,restoring aquatic biological habitats,maintaining vegetation growth,preventing soil desertification and salinization,etc.,emphasizing the prominent role of "water quantity" in the water ecological security of Tongliao City,using the ecological environment water demand and groundwater ecological water level in the river as the main characteristic values of water ecological security in Tongliao City.With the goal of ensuring the ecological base flow of the main stream of the Xiliao River and the Wuli Jimuren River,the tennant method combined with the river hydrological change-ecological response BP neural network model was used to determine the ecological environment water demand in the tongliao city river was 297 million cubic meters.In order to meet the needs of vegetation growth without causing desertification and salinization,based on the normalized vegetation index(NDVI),the quantitative relationship between the vegetation coverage rate(FVC),groundwater depth and phreatic salinity was analyzed.The threshold of groundwater ecological water level in Tongliao City is 2-15 meters.(3)Based on the relationship between water ecological security and water resources allocation,the optimal allocation model of water resources and groundwater equilibrium model are coupled,and the optimal allocation model of water resources based on water ecological security is constructed.Based on ensuring regional water ecological security,taking the optimal allocation model of water resources as the leading traction module,comprehensively using the water supply capacity analysis,water demand prediction,and groundwater equilibrium model,through data transmission and the mutual feedback iteration method of "positioning by quantity,limiting by bit",a coupling model based on the ecological environment water demand and groundwater ecological water level constraint in the river is constructed,and a coupling calculation process based on "three configurations and four judgments" is proposed,so as to reasonably determine the water resources allocation scheme of Tongliao City,and the groundwater water volume-water level "dual control" is reasonable.Indicators provide technical support.(4)Considering the constraints of the characteristic values of water ecological security in Tongliao City,this study establishes an optimal allocation model of water resources in Tongliao City based on water ecological security,and proposes the optimal allocation scheme of water resources in Tongliao City and the "double control" index of groundwater volume and water level.Combined with the administrative division,water resources zoning and groundwater type zoning of Tongliao City,this paper reasonably divides the water resources allocation calculation zoning and the groundwater balance zone,and determines that 2018 is the current level year and 2025 is the planning level year.Based on the water demand constraints of the ecological environment in the river and related planning data,this paper analyzes the water available from the sub-water source and predicts the water demand of the sub-industry in Tongliao City in 2025.On the basis of establishing the optimal allocation model of water resources in Tongliao City based on water ecological security,after "three allocations",the "double control" index of water resources allocation plan and groundwater volume and water level in Tongliao City in 2025 is proposed.In 2025,the total water supply of Tongliao City will be 2.557 billion cubic meters,of which the local surface water supply is 130 million cubic meters,the groundwater water supply is 2.281 billion cubic meters,the external water transfer water supply is 0.80 billion cubic meters,and the water supply of other water sources is 0.67 billion cubic meters.And the total water consumption of Tongliao City is 2.557 billion cubic meters,of which the domestic water consumption is 193 million cubic meters,the industrial water consumption is 118 million cubic meters,the agricultural water consumption is 2.201 billion cubic meters,and the water consumption of the ecological environment outside the river is 0.47 billion cubic meters.There is no shortage of water in Tongliao City in2025.In 2025,the total groundwater withdrawal control index of Tongliao City will be2.281 billion cubic meters,which will reduce the groundwater extraction volume by481 million cubic meters compared with the current situation.The threshold of the groundwater level burial depth control index in the plain area is 1.4-18.1 meters,and the rate of groundwater level decline in some over-exploited areas has slowed down,and the groundwater level in the un-exploited areas has risen slightly or remained basically unchanged.