Construction Of 3D Hydrogeological Structure Model For The Middle Reaches Of Heihe River Basin

The traditional hydrogeological maps express the three-dimensional spatial structure with plans,sections or borehole data,which limits the understanding of the overall regional geological conditions and the characteristics of the aquifer.In this paper,the middle reaches of Heihe River Basin(HRB)are selected as the research area.Based on the VGEOI3 D system platform,the quaternary spatial lithology structure model and the hydrogeological three-dimensional structure model of the study area are constructed and the lithology content and spatial distribution characteristics of aquifers in the Quaternary were analyzed and studied.The main conclusions are as follows:(1)By analyzing the structural model and the groundwater surface model,it is testified that the groundwater "head fall" exists in Xinba Town and Jiayuguan large fault which are affected by fault structure.(2)The accuracy of the model can be reflected by the cross-section comparison verification,and the 3D model can reflect the lithological distribution of the Quaternary and the structural characteristics of the aquifer.(3)It can be known that the main lithology of the middle reaches of HRB is gravel and gravel in the region,accounting for 36.9% and 33.7% of the total lithology of the study area,followed by sand,sandy loam and clay loam,with the lowest content of clay loam.The content of aqueous medium such as gravel and gravel is obviously more than the content of weakly permeable medium such as sandy loam and clay loam,indicating that there is a large water-rich space in the study area.(4)The lithological characteristics determine the structure of the aquifer.Among them,the gravel and gravel are mainly distributed in the top of the alluvial fan in front of the Qilian Mountain and in front of the northern hill,and the aquifer is a single phreatic aquifer.In the downstream fine soil plain area,the lithological particles become fine,and the sand gravel,sand aqueous medium and the weakly permeable medium are deposited alternately.The aquifer structure is summarized as 1-4 layers from the perspective of the region as a whole.(5)The figure-cut profile has a good overall fitting effect with the artificially drawn hydrogeological profile.The schematic section can be improving the understanding of the underground space structure and aquifer structure distribution characteristics of the study area on a microscopic level.