The Visualization Of Three Dimensional Aquifer System Based On Multi-source Data Fusion

Groundwater resources are distributed unevenly in China. Especially in recent decades, with the rapid development of industry and agriculture, the demand for exploitation and utilization of water resources initially from surface water transform into the comprehensive utilization of surface water and groundwater. In recent years, over-exploitation of groundwater is very serious, and the falling level of groundwater has induced a series of environmental disasters like surface collapse, ground fissures, land subsidence, ecological degradation, desertification and sea water intrusion and so on. Therefore, rational exploitation of groundwater has become an important topic for the current economic development. But groundwater store in underground space, it is difficult for us to form a clear understanding the space distribution of groundwater. 3D hydro-geological model not only can be used to express the groundwater storage space in the way of graphic images, but also master the migration of groundwater through the spatial analysis function of software. so 3D hydro-geological model has become a means of in-depth study on groundwater for hydrology workers, and it has been provide an important decision and technical support for the rational development and utilization of groundwater resource. But the borehole data as the primary data source for 3D hydro-geological modeling has some disadvantages including high acquisitions cost, distribution unevenly, sparse or absent in some areas and the geological information discontinuity between adjacent borehole. In the case of geological inherent complexity, ambiguity and uncertainty characteristics, it is difficult to build a relatively accurate, complete 3D model using these non-uniform, discontinuous, sporadic drilling data, and without introducing any processing and other data sources. Therefore, we selected some areas of Suzhou-Wuxi-Changzhou as the study area, we comprehensive the borehole data, profiles, geological maps and other sources of data, in order to solve the problem that the main source data is not sufficient in modeling process. In this study the main results are as follows:(1) For the problem of inadequate modeling data, this paper mainly utilized a virtual borehole and profile correction model to improve the modeling accuracy. Virtual borehole can be directly involved in the 3D model building as the same as the original borehole. In this paper, virtual boreholes are mainly used to deal with the phenomenon of the pinch out of stratigraphic, intermediate layer, borehole sparse that occurring in the processing of 3D model building. In addition, we use the geologic cross section as a boundary conditions, and in accordance with the cross section to build the boundary virtual borehole and revised the new geological cross section to improve the model accuracy. The experimental results show that: the accuracy of the model greatly improved after introduce the virtual borehole and the cross section into the modeling process.(2) In order to obtain the virtual borehole stratigraphic data, we should use the interpolation algorithm to interpolate and extrapolate inevitably. It is difficult to take into account the local characteristics of the area if we use the integral interpolation under the sample data unevenness circumstances. In this paper the study area is divided into five parts consequently. Considering the spatial distribution characteristic of data sampling points in each partition, we select the optimal interpolation method to calculate the formation data after compared the cross validation of eight kinds of spatial interpolation algorithm. Through analysis, our conclusion is: the optimal interpolation algorithm of partitionⅠis Spline with Tension(Tspline), the partition Ⅱ is Local Polynomial Interpolation(LPI), the partition Ⅲ is Universal Kriging(UK), the partition Ⅳ and partitionⅤ is inverse distance weighted( IDW). After comparison and analysis the partition optimal interpolation algorithm with integral interpolation algorithm comparison in this article show that the former can consider partial feature of the area, and has a certain advantage in the interpolation. Besides, the adaptive of eight kinds of interpolation algorithm are discussed in this paper based on the sampling points characteristics of each partition. The conclusion is that the interpolation adaptation order from strong to weak is spline function interpolation algorithm, the inverse distance interpolation algorithm, the local polynomial interpolation algorithm, the kriging interpolation algorithm, and the global polynomial interpolation algorithm.(3) The original and virtual boreholes which are through consistency processed are imported into the GMS software. we construct the 3D groundwater system of Suzhou-Wuxi-Changzhou after a series of space operations and correct teatments, and use the spatial analysis functional of GMS software to analysis the 3D model. The results of the 3D model are basically consistent with the previous survey record of the study area, which indicates that the GMS software is feasible to build a 3D visualization model, and has a high simulation accuracy.