Optimal Management Of Groundwater Resources Based On Ecological Environment In The Tongyu County, Jilin Province

Water resource is serious scarce in arid and semi-arid region where the ecological environment is relative vulnerable. Production of industry, agriculture and livestock, human lives and ecological environment are dramatically depending on groundwater. As an important environmental element, groundwater becomes more sensitive to changes of the ecological environment. Groundwater and the ecological environment are interdependent and influence each other. The contradiction of supply and need of water resources is prominent increasingly with the rapid population growth and socio-economic development. As the result of the irrational development of water resources, it will cause the change of groundwater circulation conditions and the supergene ecological environment. This phenomenon that human development activities lead to changes of groundwater and supergene ecology prevails in the north arid region.Tongyu county lies in the transition zone between arid inland and the humid area of southeast monsoon climate. Groundwater is an important water source in local area. Since the past 20 years, the eco-environment is worsened continually.A series of increasingly serious ecological problems has emerged, for instance, sandlot and salt and alkaline land increase, the area of meadow, water and wetland decrease rapidly. Therefore, there is a need for carrying out the coordinated study about regional groundwater resources development,socio-economic and development of ecological environment and determining the program of reasonable exploitation of groundwater. It is of great significance of improving the regional ecological environment and socio-economic sustainable development.Directed toward the supergene ecological effect excited by groundwater, the paper, for the purpose of maintaining sustainable exploitation on groundwater and ensuring coordinated development of ecological environment. The ecology-oriented groundwater resources optimization management model was established. Based on the theory of hydrogeology and eco-hydrogeology, several research aspects were carried on by means of remote sensing, the coupling between groundwater flow numerical simulation and optimization model and GIS technical methods.The change of supergene ecological landscapes is the result of both nature condition and human activity. It is a major feature of the degree of eco-environmental vulnerability. At first, the paper analyzed the distribution and changes of ecological landscapes. RS and GIS techniques were used to translate ecological landscapes from remote sense image of 1989, 1996 and 2004 in Tongyu. Ecological landscape maps provided a great deal of basic data for the analysis of the characteristics of landscape elements. The features of ecological landscape were showed with the spatial overlay and statistical analysis functions of GIS. The studies have shown that the main landscapes of Tongyu appears "three increases and three decrease" in quantity in recent years. "Three increases" means cultivated land, woodland and salt and alkaline land increase, "three decreases" means the area of meadow, water and wetland decrease. The main cause is that irrational development and utilization of groundwater resulted in the change of water depth and water cycle. On the basis of above analysis, this thesis researched on the relationship between groundwater and ecological landscapes of surface. Three run-off sub-zones were delineated basising on ecological landscape maps, water depth and groundwater flow field. In each zone, characteristics of landscape elements (water, wetland, woodland, meadow, salt and alkaline land, sandlot, cultivated land) in groundwater recharge, transition and discharge areas were discussed separately. Finally, the appropriate depth of water level was determined for maintaining optimal circulation of eco-environment in each zone.In accordance with the steps of groundwater management model, groundwater flow numerical simulation model should be established firstly. The main simulated aquifer is Quaternary water table aquifer and confined aquifer in this numerical simulation model of groundwater. Between water table aquifer and confined aquifer is aquitard which is composed by mild sand clay and mild clay of mid Pleistocene series. They have unified hydraulic connections, which constitute a quasi-three-dimensional flow system. The groundwater flow was simulated by the software MODFLOW. The area of the calculated zone is 8496 km~2, the software used the finite difference method to calculating, partitioned by rectangle. The simulation period was from 1999.11 to 2000.11. The time from 1999.11 to 2000.4 is used to diagnosis the model and the time from 2000.4 to 2000.11 is used to verify the validity of the model. Run the model, diagnose the model parameters by fitting the fact and the calculating groundwater flow field; run the diagnosed model, check the model again. The results indicate that the model can be realistic portrait for characteristics of groundwater system of the study area. It laid the foundation for the solution of response matrix.The key to water resource management is the groundwater optimal management model. The responding matrix method is applied to establish the model for groundwater resources. The responding matrix is gained by solving the checked the quasi-three-dimensional flow model in this thesis. Then the method was presented for constructing response matrix approach in a two-aquifer system by employing the simulation model and treated two-objective management problems as a linear programming problem in order to solve it easily. Based on the above research, groundwater optimization management model for the ecological environment had been set up. In the model the minimum water level drawdown under meeting water demand was set as the objective function and the ecological water level and scheme water were adopted as the constraint condition. In addition, ecological water level was determined in accordance with the results of the analysis of Chapter III.Optimal exploitation was calculated under current situation through solving the management model, source of water table aquifer for the exploitation of areas in section 3, 5, 6, 8 and 9, source of confined aquifer for the exploitation in 12 zones. The exploitation of each zone amount to 1.625×10~4m~3/d, 0.805×10~4m~3/d, 6.667×10~4m~3/d, 2.85×10~4m~3/d, 3.095×10~4m~3/d, 3.509×10~4m~3/d, 1.824×10~4m~3/d, 2.723×10~4m~3/d, 1.885×10~4m~3/d, 2.167×10~4m~3/d, 0.931×10~4m~3/d and 1.919×10~4m~3/d from 1 to 12 partitions. Supergene eco-environmental problems were taken into account in the process of groundwater exploitation in the model. It provides a valuable, viable and practical approach for protecting the ecological environment and optimal circulation of eco-environment. Further more, the paper considered endemic disease caused by high concentration of fluoride and arsenic in Tongyu county. Drinking water security can not be ignored in this area in view of poor water quality in this area. Consequently, the author made a brief analysis of water quality of the study area. To ensure drinking water security, water treatment and control measures should be carried out in the implementation of management program.The thesis highlightst considering groundwater as an integral part of ecosystems, studying on the groundwater management model for groundwater coupled with the ecological environment, using remote sensing technology and GIS technology. However, limited to the lack of the raw data and other reasons, it failed to establish groundwater management program under different situations and assess the future. In the full information, we will continue to improve. The study is an attempt to the coordinated development of groundwater exploitation and eco-environment protection, providing a new idea for the research of maintaining sustainable exploitation on groundwater, meanwhile, providing a reference for improvement and construction of the ecological environment.