A Study Of Numerical Simulation For Groundwater Flow In The Beijing Plain

In Beijing, the production volume of groundwater hits 2/3 of the water totally supplied,so Beijing's water supply mainly depends on the groundwater extraction. Actually theaverage per person holds only 300m3 groundwater a year in Beijing, so Beijing is lack ofwater compared other metropolises. Since 1999, the continuous drought and the increasingwater consumption have intensified the scarcity of water resources and made the waterenvironment problem more serious. It is very important to set up the groundwaternumerical simulation model so as to study precisely groundwater resource and providedecision supports for allocation of surface water and groundwater.After the data, including: meteorology, hydrology, geology, topography, hydrogeology,groundwater exploitation, is collected and analyzed, the groundwater model of theQuaternary aquifer is built up by GMS software. In this procedure of setting up the model,the Solid model, which can reflects the aquifer structure, is also built up. The aquiferstructure is conceptualized based on the understanding of aquifer structure and theconvenience of using software. The upper boundary of the model is phreatic surface. thebottom boundary is the base of the Quaternary. The boundary of mountain and plain isconceptualized as inflow or outflow boundary. The administrative boundary at the southand east side is conceptualized as general head boundary. The whole model is characterizedby five transient flow aquifers which are continuous, heterogeneous, anisotropic, threedimension. The steady and transient flow models are set up by using the data in 1995 and1992 separately;finally the transient model is certificated by the data in 2000. The builttransient model can reflects the groundwater moving character, so it can be used to predicteffectively the future groundwater level. Three scenarios of exploitation for water plants aremade out based on the analysis of precipitation and future extracting situation. The watertables under those three scenarios are predicted by the built transient flow model.During the study, the steady flow model was built and then the transient flow model.These could avoid the troubles of multi-parameter calibration in the procedure of setting uptransient flow model. The groundwater dynamics can be predicted effectively and thegroundwater resource can be evaluated by using the built model.By thinking of the geo-environment problems caused by the decrease of water level, inthe future the extraction rate of groundwater source plants should be reduced by at least30% of the rate in 2000.