Clines in salt lakes in the Badain Jaran Desert and their significances in indicating fresh groundwater discharge

A number of salt lakes exist in the Badain Jaran Desert that located in the Alxa Plateau,China. To reveal the stratification characteristics of salt lake water and the impacts of groundwater to the lakes,a survey of the depth-dependent temperature and electric conductivity in September was carried out in the second largest salt lake: the Sumu Barun Jaran. Thermocline is observed even though the lake has a big wide / deep ratio that is higher than 90. The salinity( TDS) varies from 60 to 160 g / L,exhibits a relatively strong spatial variation. Abnormally low TDS zones exist near the lake bottom,forming chemocline in the themocline,which is considered to be influenced by concentrated discharge of fresh groundwater. This type of sub-lake springs have also been observed beneath shallow water bodies in other salt lakes,showing that both shallow and deep groundwater contribute water and salts into the lakes. Variation of temperature versus depth in the thermocline approximately satisfies the heat transfer in a static water body,is not significantly influenced by heat transfer from groundwater discharge. Further investigations are required for the seasonal variation patterns.