Application of Visual MODFLOW to the dynamic change and simulation of deep groundwater in Dezhou City,China

摘要

In view of this major environmental geology problem in Dezhou City that continuous overexploiting of deep groundwater has caused he rapidly-expansion of groundwater drop funnel in recent years,the dynamic change of deep groundwater in Dezhou City was systematically analyzed as well as the evolution and development of hydrodynamic field and deep drawdown cone in temporal and spatial variation was simulated by the application of the numerical Model.On the basis of hydrogeological conditions generalized in this region,Visual MODFLOW software was applied to build mathematical model of groundwater and stimulate the seepage field of groundwater.It predicted the expansion of groundwater drop funnel and the change of underground water level under the conditions of exploitation situation and different designed exploiting volume by the model built.The depth reduction and variation of groundwater under different design schemes for pumping rate were argued by contrast analysis of the calculated results.The forecasting result under the current situation of groundwater exploitation indicates that the drawdown of water level would increase more with the continuous exploitation when the exploiting volume of current situation is 2047×l04m3/a.When t (time) is equal to 5a (2013),s (the decline depth of groundwater) is at 4.81 ～22.65m and the annual deceleration is at 0.96～4.53m/a.When t is equal to 10a(2018),s is at 14.32～32.87m as well as the annual deceleration is at 1.43～3.29m/a,and then the average elevation of central water level of funnel is -118.06m.The forecasting results under different design schemes for exploiting volume showed that the groundwater level would continuously decrease if the present exploiting quantity is still kept at 2047×104m3/a,which the depth of central groundwater level of funnel is 144.95m in 2012.While exploiting quantity cuts down to 1950×104m3/a,the groundwater level still constantly decreases,which the depth of central groundwater level of funnel is 133.90m in 2012.Only when exploiting quantity further cut down to 1750×104m3/a,the groundwater level would never descend after 2011,and then it would begin ascending,which the depth of central groundwater level of funnel would be 120.25m in 2012.According to the model stimulation of groundwater flow and the results of water balance analysis,the exploitation project was proposed that the drawdown cone would not further expand.The key measure to protect deep groundwater resources in this region is scientific planning of underground water,and ensuring that The allowable exploiting volume in this region should be kept at 1750×l04m3/a in order that it can reach a benign circle with the balance of exploitation and supplementation.