Internal structure of sand dunes in the Badain Jaran Desert revealed by GPR and Its implications to inter-dune lake hydrology

Badain Jaran Desert in northwestern China has the world´s highest stationary sand dunes, which are up to 500 m tall from bottom to top. Despite the prevailing dry and windy climate conditions the mega dunes were relatively moist underneath a dry surface layer of less than 1 m. It is very common to find a salt lake directly at the foot of the leeward side of a mega dune. Using 50- and 100-MHz antennas we have conducted ground penetrating radar (GPR) surveys on both the windward and leeward sides of the mega dunes in southeastern Badain Jaran Desert. The GPR surveys clearly revealed the existence of numerous, almost evenly spaced bedding features on the windward side of the mega dunes. The reason for the existing beddings is on the leeward side sand dune surface can be cemented by moisture with annual precipitation and the caliches generated by these calcareous cement will be likely inducing more infiltration flow toward the leeward side and consequently channeling more recharging water to the lake than to the windward side. This trend may be one of the key factors that kept the lake exist in a very arid environment with high evaporation rate. The GPR profile also clearly revealed the shape of the water table beneath the mega dunes, which is gradually elevated toward the peak area from both toes, implies that the desert lakes are possibly recharged at least partly by the groundwater from the precipitation. Numerical simulation reconstructed the proposed internal structure.