Numerical Simulation Of Controling Saltwater Intrusion In The Downstream Of Zi River Reservoir

Sea water intrusion is the phenomenon of environmental degradation in coastal areas that due to natural factors and human factors,made the coastal area of hydrodynamic conditions changed,and break the old dynamic equilibrium between the underground fresh water and sea salt water,finally caused salt water infect to the Fresh,and salinization gradually,while affect the industrial and agricultural production and living;Natural factors such as rising sea levels,tides,wind direction and so on.Human factors is a major factor that over-exploitation of underground water which caused significant decline in groundwater level.Study area include the south of Guangrao County and which located in the downstream of Zi River Alluvial Plain,is the only shallow fresh water reserves of the Yellow River Deltas,and the important industrial and agricultural economic zones;Due to population growth,expansion of industrial and agricultural production,since 1975,because of over-exploitation of shallow underground water,resulted the southern irrigation area formed groundwater drawdown funnel,groundwater flow changed from northward to southward,resulted the north of salt water invasion;Saltwater intrusion front line(250mg/l contour of Cl~- concentration) roughly in a wide Guangrao County of Qianyan-Xiaojia-Yanxu-Gaowan, extending across the Zi River to the Shouguang City area.Currently,to supply industrial water and river landscape,Guangrao water sector built a reservoir in the Zi River which the water from the Yellow River,while at the same time reservoir water recharge a large number of water to the groundwater.This thesis is based on Public service sectors of Ministry Water Resources"Optimal Water Resources Allocation and Adaptive Technology In Yellow River Water Resources",and fully investigated of meteorological,hydrological,geological,hydrogeological conditions and groundwater observation information and monitoring water quality data (Cl~-),and other first-hand field data which obtained by field measurements,including select the monitoring section to measure the water level and test the water quality(Cl~-),use the Gamma probe detection of the Auslog geophysical logging system to probe the selected typical profiles,in order to know the dynamic changes in salt and freshwater interface. Finally use the Visual ModFlow4.2 software to build mathematical model,established a three-dimensional unsteady flow and variable density solute transport model,including to determine the scope of the simulation,overview the aquifer,establish the boundary conditions and handle the source and sink terms,use the long view groundwater well data,Cl~- concentration data from 2005 to 2009 as the fitting basis,adjust the parameters, identify the model,and use the data to verify the model,simulate the intrusion of salt water,not only to simulate the process of river-type reservoir effect on salt water intrusion,but also predicted the conditions of guaranteed rate of rainfall 25%,50% and 75%,the effect of river-type reservoir prevent salt water intrusion.Operating results are accurate and intuitive,Analysis of three kinds of schemes and indicate that at this three conditions of guaranteed rate of precipitation,under the conditions of river-type reservoir ensur the amount of the water,Cl~- 250mg/l conter concentration have the same trend by 2015.But in this three trend assurance conditions,due to ground water supplies, reservoir reservoirs have obvious back,but in this three conditions,because of the recharge of reservoir,saltwater intrusion area reduced,and the 250mg/l contour of Cl~- concentration back obviously where around the reservoir.so as to provide a scientific basis and programs for further prevent the salt water intrusion,and at the same time protect the natural ecological environment of the region while develop the industrial and agricultural production,achieve the strategy of sustainable development Yellow River Deltas.