The interaction and the interface migration between salt lake water and fresh groundwater in small salt lake: a case of Lake Cherigele, Badain Jaran Desert, China

Abstract

The salt lakes in arid deserts serve as crucial ecological resources and tourist attractions. However, due to the limitations of aeolian sand cover, it is challenging to directly investigate the underground contact relationship between lake water and groundwater. In the Badain Jaran Desert (BJD) of China, the fresh groundwater near salt lakes is the sole source of drinking water. Consequently, a pressing concern arises regarding how groundwater exploitation impacts the intrusion of salt water into groundwater. In this study, Lake Cherigele (CRG) was chosen as a case to investigate the characteristics and migration mechanisms of the saltwater-freshwater interface using numerical simulation methods. The results reveal that: (1) The saltwater-freshwater mixing zone exhibits a wedge-shaped morphology, with a length of 250 to 290 m and a depth ranging from 50 to 70 m within the model. (2) The hydrodynamic conductivity coefficient (K) of the sand layer and molecular diffusion coefficient (D_m) in the desert are identified as the primary parameters influencing the characteristics of the interface. (3) The annual fluctuations in the current groundwater level have a limited impact on the saltwater-freshwater interface; however, excessive groundwater exploitation can lead to the intrusion of salt water into freshwater body. (4) The density difference between groundwater and lake water results in the concentration of groundwater flow lines around the lake, giving rise to the numerous springs observed in the field.