Study On Numerical Simulation Of Groundwater Recharge In Plain Area Of Beijing

With the fast development of urbanization and the ever-increasing population inBeijing, the problem of water shortage is becoming increasingly prominent. In orderto meet water demand in Beijing, the groundwater exploitation had been increased farbeyond the available quantity which could cause series of problems such as groundsettlement, groundwater pollution, ecological environment problem and so on. Whilethe Middle Route Project of the South-to-North Water Diversion brings one billioncubic of water in2014, the water supply structure will be changed and it becomespossible to restore the groundwater level with recharging. However, the matching ofthe water from South-to-North Water Diversion Middle Route Project and the localacceptable adsorptive capacity in Beijing, appropriate place and way, quantity ofwater, even the effect for the groundwater recharge all need to be studied.This article firstly introduced the hydrogeological characteristics andgroundwater’s feature of Beijing plain area detailedly. After Conceptualization of theaquifer structure and boundary conditions, three-dimensional unconfined aquifergroundwater flow model of the study area is set up by FEFLOW which is agroundwater numerical simulation software. The model was calibrated by thehydrological data of1992, which determined the hydrogeological parameters of themodel. Then the model was validated by the hydrological data of2000and thesimulated groundwater field fit well with the measured result. After analyzing thefuture water supply and demand in Beijing and prediction of groundwaterexploitation, different groundwater recharge scenarios under different situations areproposed and simulated by former flow model. Set up corresponding Solute transportmodel through which a representative program would be simulated to analyze theinfluence of the groundwater recharge to the local groundwater.Results from this study showed that, if the recharge capacity of the place isacceptable, more water recharged into the recharge place, more extensive therecharge area will be and more higher the water level will rise. The effect of the groundwater recharge in Yongding River underground reservoir was better than otherrecharge places in restoring the groundwater level of plain area. There are three betterprograms under different rainfall levels. Compared with the water level with norecharge, the highest water levels were increased by24.65m,29.79m and23.63m,and the lowest water levels were increased by7.26m,5.47m and5.38m.Without consideration of other serious pollution sources, sorption andbiodegradation in the groundwater, the recharge water quality would influence thelocal groundwater quality in less than approximately58square kilometers around therecharge place. The concentration of TDS and nitrate nitrogen of the recharge waterwould cause the concentration of the same solute from nearby groundwater decreaseby diffusion and hydrodynamic dispersion, while the concentration of total hardnesswould increase the concentration of the same solute from nearby groundwater.