Research On Chengdu Plain’s Aquifer System Structural Model Based On GIS

Based on regional geological data, to establish groundwater numerical simulationis the development trend of groundwater management, especially important for thesustainable exploitation. Therefore, the process of regional groundwater numericalsimulation is particularly significant, and before taking some measureswe need tohave a full understanding of the regional hydrogeological conditions via theestablishment of3D geological model. Chengdu Plain as the main area of economicand cultural development in Sichuan Basin, various construction projects are builtfrequently. By studying mine, water conservancy, water hydrology and geology in thepast30years as well as large-scale urban exploration process in recent years, there aretens of thousands of drilling accumulated within the scope of the whole plain. It willbe a great progress for the work of geology and hydrology in Chengdu Plain, if thesedrillings results can be used to establish a complete database.Through the analysis of existing geological data in the Chengdu Plain, ChengduPlain Quaternary aquifer system, based on the lithologic characteristics, is dividedinto two systems, upper and lower. Meanwhile, according to available drilling data ofthe area, we have divided aquifer and aquifuge among each borehole, and countedelevations of each layer. Space of the aquifer system model is established by usingArcGIS software to realize the3D visualization of Chengdu Plain aquifer system.Then using the spatial analysis function of ArcGIS to analyse the surfacehydrologyical data of Chengdu Plain, the slope of each aquifer, and the key regionalprofile. Finally, we will get to the Chengdu Plain aquifer system model, combinedwith Modflow groundwater simulation software, to simulate the seepage fieldcharacteristics of Chengdu Plain under the natural conditions.Through the studies above, the following results and conclusions have beenobtained:(1)Upper aquifer in the Chengdu Plain is Holocene alluvial gravel cobble layerand upper Pleistocene ice water accumulation of mud gravel; the lower aquifer is lowPleistocene silt sandy gravel. Between the two distributions there is a more completeaquifuge. Middle and lower Pleistocene glacial sediment contains gravel, whichmakes the two water systems independent, and weaken the hydraulic connection. (2) By means of the surface DEM hydrological analysis, we have obtainedthe accumulated figure of Chengdu Plain surface drainage flow and the watersheddivision figure. It is comparatively clear to describe the Tuojiang river system innorthern and southern Pujiangin accordance with the real situation, but due to thelimited accuracy of the data, the complexity of central plain in Minjiang river areafeatures has the certain errors compared with the realities.(3)Compared the ArcGIS spatial analysis results with measured profile results ofthe previous regional census, the results of this model show the distribution well inlarge scale among Chengdu Plain aquifer. It can be used in large area. We willunderstand clearly the distribution of the Chengdu Plain aquifer and aquifuge by themodel. Meanwhile, based on geographic information system, a real Quaternaryaquifer system in the Chengdu Plain is restored, it can also be distributed moredetailed modeling of small-scale aquifer for each specific area, and then compare thedifferent regions to make the accuracy of the results smaller.(4)The “.grd” file is got after the conversion of ArcGIS and Sufer grid file, so asto realize the combination of ArcGIS and Modflow. Through the model generalizedwe have got the natural seepage field under the condition of the Chengdu Plain. Onthe plain, groundwater flowing direction is consistent with the surface water, mainlyfor supplies for the plain on the west side of North Piedmont Plain. It flows fromNorth West to South East runoff, controlled by the surface water on the plain. Jintangand Xinjin become groundwater discharge level.Groundwater is also the same assurface and flows out of the plains.Based on the groundwater system of GIS, the established model on ChengduPlain has successfully realized the3D visualization of Chengdu Plain aquifer system.By displaying the visualization of results, we can know Chengdu Plainhydrogeological structure more visible, and the realization of the model, combinedwith Modflow, provides a new technology for groundwater resources management,and make a hit of geographic information.