Numerical Simulation And Evaluation Of Groundwater In Baicheng City

The title of this thesis is selected on the basis of the item for science andtechnology development plan of Jilin province "Research on zoology buildand the measure of water resource collocation in the Western arid of JilinProvince" (Item NO. 20020406) and the item of China Geological Survey"Research on the subject of water resource and environment problem inSongnen Plain" (Item NO. 200310400018).The main simulated aquifer is Quaternary water table aquifer and confinedaquifer in this numerical simulation model of groundwater.Water table aquiferincludes the water-bearing sand seam of Holocene series,upper Pleistoceneseries and upper part of the mid Pleistocene series;confined aquifer includesthe sand seam of under mid Pleistocene series and down Pleistocene series;between these two aquifer systems is aquitard which is composed by mildsand clay and mild clay of mid Pleistocene series. Calculated aquifer can begeneralized to be heterogeneous and isotropy aquifer. The flow is unsteady incurrent time and forecast period.The water table aquifer boundary which is connected with bedrock is animpermeable boundary, the others are first boundary that the water level isknown. Confined aquifer boundary are all fist boundary. In vertical, the upside of the water table boundary is a water exchange boundary, lower side is alow permeability boundary;the up side of the confined aquifer boundary is alow permeability boundary, the lower side is an impermeable boundary.Based on the above research, the author built the mathematic model ofgroundwater flow system, simulated the groundwater flow by the MODFLOWpart of GMS4.0 (Groundwater Modeling System). The area of the calculatedzone is 23 813 km2, the software used the finite difference method tocalculating, gridding by rectangle, the total knots are 9334 and the totalelements are 9138. The simulation period was from 1997.11 to 1998.10, everytime interval is a month and every 5 day is a time step. The time from 1997.11to 1998.3 is used to diagnosis the model and the time from 1998.4 to 1998.10is used to verify the validity of the model. Combine the hydrogeologiccondition with the landform condition and the aquifer character, the authordivided the water table aquifer into 11 parameter partitions and the confinedaquifer into 10 parameter partitions. The inflow from the groundwater systemupper boundary included precipitation infiltration, irrigation infiltration, riverand ditch leakage, the outflow included evaporation and exploitation. Themainly recharge of the confined aquifer is the flow from the upper boundaryand discharge of the exploitation in the natural. Run the model, diagnose themodel parameters by fitting the fact and the calculating groundwater flow field;run the diagnosed model, check the model again.The period of water table predict is 2005~2015 which base on the nationaleconomic plan of Baicheng city. On the condition of planning exploitation, thewater level generally falls about 1m off in the study area, the maximal fallingextent appears in the adjacent of Tao'er-River fan and Taonan and Zhenlai.The author simulated the water table aquifer which NO3 ? is existed in as themajor aquifer.This calculation simulated the groundwater flow by the MT3DMS part ofGMS4.0. The software used the MOC method to calculating and the finitedifference method to calculating the change of concentration which caused bythe dispersion. The simulation period and the time step.are the same as thegroundwater flow model, the dispersion parameter partitions are the same asthe permeability coefficient partitions. The initial value of the parameter ineach partition was decided by field dispersion experiment result. Thecontamination of NO3 ? is mainly from fat used in the agriculture in the studyarea, the major outflow is flowing with the ground water. Run the model,diagnose the model parameters by fitting the fact and the calculatingconcentration isoline;run the diagnosed model, check the model again.The predict period of water quality is 2005~2010. The concentration of?NO3 in the study area is rising slowly by the contamination of fact in currentaccording to the result of the water quality prediction. The concentration of?NO3 in the adjacent of Baicheng city last rising in a large extent affect by thepoint contamination.The author suggested reducing the exploitation of the ground water andmake use of the surface water instead. To reduce the contamination of theground water, the using of the fat in agriculture should be used in science andthe impermeable measure should do well in the rubbish field too.