Study Of The Groundwater Hydrodynamic Field And Balance Evolution In The North China Plain Based On Numerical Modeling

With the high development of human society,human activities bring unprecedented effect on groundwater in North China Plain(NCP)during the recent fifty years,and focus on the impacts of human activities on groundwater has become a social concern.Based on the groundwater numerical simulation technology,this paper uses the GMS software and improved Modflow2005 program to construct the numerical model of regional groundwater flow of the NPC respectively in the natural state and under the influence of human activities with a long time series from 2000 to 2010.This model simulates the flow field and the dynamic change of groundwater in NCP.It quantitative analyses the impact of human activities on groundwater circulation and the composition and variation of groundwater recharge and discharge,to lay the foundation for the further quantitative understanding of water resources in NCP and provide important scientific guidance for reasonable exploitation and utilization of groundwater resources.This paper analyzed the change of groundwater flow in two modes.By the analysis,flow trend of the groundwater flow field in NCP changes little affected by human activities.It flows almost from the west northwest and southwest to eastward.However,human intervention makes the local groundwater flow become complex,local hydraulic gradient increase,or the groundwater drawdown funnel.It then change the flow direction of groundwater.Using the simulation results,we carry out the quantitative research on the balance of groundwater in the study area and make equilibrium analysis both by layers and by administrative regions of the recharge and discharge of groundwater in the natural state and the period from 2000 to 2010.On this basis,groundwater recharge and discharge of the two models is analyzed and compared.The average total recharge of groundwater is 237.03×108m3/a in 11 years from 2000 to 2010,and the total discharge quantity is 271.79×108m3/a.Compared with the natural state,the total recharge increased 97.94×108m3/a,total discharge increased 133.83×108m3/a.The transition from the recharge and discharge of groundwater balance is negative equilibrium state.The precipitation infiltration amount is the most important source in the study area and it increases from 118.10×108m3/a in the natural state to 179.38 x108m3/a average from 2000 to 2010.Agricultural recharge gradually become one of the main recharge sources of the study area.Exploitation of groundwater is an important driving factor of groundwater evolution.Artificial exploitation leads to the decline of groundwater level.Groundwater evaporation amount is greatly reduced,making groundwater which was dominated by evaporation of phreatic water excretion in natural state gradual evolution of artificial exploitation.The average annual evaporation is 57.69×108m3/a in 2000-2010 years.It bears a decrease of 79.50×108m3/a compared with the natural state evaporation which is 137.20×108m3/a.The NCP shallow groundwater exploitation is composed by the storage capacity of incremental supply,natural excretion reduction in exploitation conditions and mining in the funnel,the proportion is respectively 54.04%,32.91%and 13.05%.