Hydrogeology Digitization And Groundwater Numberical Simulation Of Tianjin

Water resources are extremely scarce in Tianjin,though the South-to-North Water Diversion Project started to supply water in December 2014.For long-term groundwater overexploitation,many environmental-geological problems occur,such as land subsidence,seawater intrusion etc.So it is necessary to establish a scientific groundwater management information system.Around the main problems to be solved in the development and utilization of groundwater,the study starts.After the deep analytics of the hydrogeological conditions,the digitization of hydrogeology began.The hydrogeological conditions were divided into three parts in the study: the hydrogeological structure,the groundwater flow field and the water level dynamics,and the groundwater chemistry.SURFER and MAPGIS software was used to draw the hydrogeological space graphs,including the aquifer isopach maps,the isobaths maps of aquifer,the zoning maps of hydrogeological parameters(including infiltration coefficient of precipitation,irrigation return flow rate,hydraulic conductivity,specific yield,storage coefficient etc.),the groundwater level contour maps,the hydrogeochemical maps of groundwater and so on.The hydrogeological spatial database was established by the secondary development of MAPGIS and ACCESS with Visual Basic 6.0,which could conduct both spatial data and raw data.Based on the data and space graphs that provided by the database and GMS software,groundwater numerical simulation model of Tianjin was constructed.This model selected January of 2011 to December of 2013 as the simulation period.The trial and error method was used to fit flow field and hydrograph of the simulation period by adjusting the hydrogeological parameters.And then ran the corrected model to calculate the groundwater balance in the testing period.The average recharge value of groundwater system was 17.72 × 108m3/a,and the average discharge value was 17.40 × 108m3/a,which means the recharge and the discharge was almost in balance.The result of equilibrium analysis was consistent with the actual situation,which further proved the reliability of the model.In the study,the hydrogeological spatial database is established,which will conducive to the scientific management of hydrogeological data and the establishment of the groundwater numerical model,also provides the basis for the utilization and management of groundwater resources in Tianjin city.