Elements Content And Genesis Of Natural Water In Upstream Of Upper Reaches Of Han River Basin

The Danjiangkou Reservoir in the mid-section of Han River in south Qinling-Daba Mountain is the main water source of China’s South-North Water Diversion Project,which has transferred about 35 billion cubic meters of water,providing 73%of Beijing’s drinking water.In order to study the elements content and water quality of upper reaches of Danjiangkou Reservoir of Han River,upper reaches of Han River Basin was chosen as the main research area,and Wei River Basin,Chaobai River Basin,Baiyangdian River Basin,Gongnaisi River Basin and Lian River Basin were chosen as the comparison area.A total number of 472 natural water samples such as groundwater,surface water and mineral water were collected.The content of main ions and trace elements were detected.The results showed that:（1）The hydrochemical type of natural water in all the study areas were mainly Ca²⁺-HCO₃^-type.The chemical composition of natural water in upper reaches of Han River Basin were mainly Ca²⁺,Mg²⁺and HCO₃^-,followed by SO₄^2-,and TDS was low,all samples were fresh water.The Wei River Basin has the highest content of major elements,and the content of all elements in natural water of Lian River Basin were lower than other basins.（2）5.12%of the samples meets the standard for Se-type mineral water,38.6%of the samples meets the standard for Sr-type mineral water,and 11.16%of the samples meets the standard for H₂Si O₃-type mineral water.The health index in the area was high,and there were rich mineral water resources.（3）The ion content in Du River Basin,the largest tributary of the Han River,vary greatly from year to year.Contents of HCO₃^-,V,Ti,Na and SO₄^2-were higher in the months with heavy rainfall,while the contents of TDS,U and Mo were lower.Beijing’s drinking water,mixed with"southern water",contains more beneficial elements such as Se,Sr,Li and Zn than Beijing’s groundwater.The South-to-North Water Diversion Project had brought many elements to Beijing.（4）Water in the studied area is greatly affected by carbonate rocks and silicate rocks,and the ions in water may mainly come from the dissolution of calcite,followed by dolomite,sodium feldspar and magnesium sulfide.（5）The content and combination of trace elements in different areas of the upper reaches of Han River Basin vary greatly,and are mainly related to the lithology and lithofacies of the basis strata.The Se-rich and Zn-rich water were distributed in the area where the black rocks of the Cambrian Formations with high content of Se and metal elements are distributed.Water in the upper reaches of Han River Basin has low Na content and high Se and Sr content.And has the potential for the development of natural Se-type mineral water and Sr-type mineral water.