Application Of Multivariate Statistics Method Into Research On Spatial Distribution Law Of Hydrochemistry In Groundwater System In Zhangye Basin

Zhangye basin is Located in the middle reaches area of heihe river, which is a typical Little rainfall, evaporation, and strong drought area in the hexi corridor plain of northwest in China. It is not only the main zones of population and industrial and agricultural production in heihe river basin of northwest inland, but also the seeds of main base in our country. The Less rainfall and strong evaporation, water resources shortage, severe desertification, water pollution problems also appear frequently. Therefore, the study of Zhangye basin groundwater hydrochemistry distribution to the sustainable development of Local social economy and maintain the balance of the ecological environment is of great significance.Based on the collecting of predecessors in the study area, such as the topography and geomorphology, geological structure, meteorological and hydrological data and groundwater chemical materials, related Literature at home and abroad, and the field survey to collect hydrochemical samples and data analysis, carrying on a study of Zhangye basin groundwater hydrochemistry distribution.Applying the surfer8.0 software to generate the shallow and middle water chemistry major ion content in the sample and TDS distribution contour map and the application of statistical methods of different samples of water chemical composition analysis of the research area, respectively, to study the shallow, middle and deep Layers of main chemical composition of groundwater and the hydrochemical types of the distribution and change rule in horizontal direction and vertical direction. The results showed that the shallow and middle groundwater TDS distribution in the study area are presented obvious zoning Laws, outside from the qilian mountain to mountain were gradually increased. Each main ion distribution trend is: in the shallow groundwater distribution of Na⁺, SO₄^2-, Cl- presents obvious zoning Laws, other ion distribution of each different, groundwater in the middle of each ion content is generally Low shallow groundwater, NO₃^- content in the area of intensive human activities. In the vertical direction, the characteristic of groundwater differentiation is obvious, the groundwater in the vertical direction, mainly supplied by jacking of bottom-up Leached effect is the region’s main influence factors of groundwater chemical formation, and the content of major ions in water, TDS decline with the increase of depth. The main hydrochemical type in the study area is HCO₃^-type, and presents a hydrological geochemical zoning characteristics along with the groundwater runoff discharge path obviously. Shallow groundwater hydrochemistry type is more complex, and compared to the shallow groundwater, SO₄^- type water area increased in the middle Layer, and no Cl-type water appear.In addition, this article selects the Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl^-, SO₄^2-, HCO₃^-, TDS, T-hard, PH value as the initial variables of correlation analysis, cluster analysis and factor analysis, in the shallow and middle groundwater hydrochemical samples of multivariate statistical analysis. Classifying hydrochemical samples first, understand the general distribution characteristics, and then extracting the main factor in the formation of water field, comprehensively analyzing the groundwater hydrochemistry formation in the study area. Results showed that the main factors influencing the shallow groundwater chemical characteristics is Leached, evaporation and mixing action; The deep groundwater chemical characteristics mainly effected by the environment of geological history and the flow of the supply of the shallow groundwater and its effect on shallow groundwater of jacking.