| Badain Jaran Desert is the second largest desert in China,with extremely dry climate.The desert is famous for its high sand mountains and numerous lakes.The lake-centered wetland is not only a tourist landscape,but also a habitat for desert animals,plants and human beings.The Sumujaran lake basin in the southeastern badain Jaran desert contains two lakes,southern lake and northern lake.The area of the southern lake is about 1.24km2 and the maximum water depth is more than 10m,The area of the northern lake is 0.59km2 and the average depth is less than 10m.This research focuses on the southern sumujaran lake.In this paper,a typical section is selected in the north of the Southern Sumujaran lake for data collection,field sampling and laboratory experiments to obtain basic data.The characteristics of groundwater environment and characteristics of lake water level fluctuation zone?LWLFZ?are obtained by analyzing the water level?lake sediment and pore water.The results are helpful to deepen the understanding of the hydrological and water environment characteristics of lakes and wetlands in the Badain Jaran desert.This paper summarizes identification methods of LWLFZ and discusses advantages-disadvantages and applicability of each method.The slope of typical lakeshore profile was obtained by topographic survey method,and the width of LWLFZ was speculated to be about 20 times that of lake level variation.By analyzing water level data,the characteristics of LWLFZ at different time scales are obtained.The daily variation of the water level is in centimeters,and the width of the daily LWLFZ is in decimeter to meters;The inner-annual variation of the water level is in the order of decimeter,and the average width of the annual LWLFZ is close to 5m;In the past five years,the water level fluctuation amplitude does not exceed 1 m,but the width of the inter-annual LWLFZ could be 7m.The sedimentary history was preliminarily inferred by analyzing the organic matter content of sediment grain size and 14C data,indicating that the climate was relatively warm and humid during 3000 to 4200cal a BP,and then the Badain Jaran desert turned to an arid climateic environment.The climate changed from dry and cold to relatively warm and humid after 1350cal a BP.A cross section was established for the main ion content in the pore water of sediments.It is indicated that there are significant spatial variations in the ion concentration of groundwater at different locations and depths.The concentration of groundwater TDS ranges from 0.5g/L to100g/L.Within a depth of 1m,the interface between saltwater and freshwater is nearly vertical and slightly inclined to the far shore.The intersection of saltwater and freshwater interface with lakeshore is approximately controlled by the highest water level in a year.Analyses of stable isotope characteristics of water samples collected from well and lakeshore sediments show an enrichment of heavy isotopes due to evaporation effect.After groundwater discharging into lakes,the secondary evaporation of lake water is obvious,with more enrichment of heavy isotopes. |
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