Observation Experiment Of The Water Cycle And Lake Water Balance In Alxa Desert

The main climate and hydrological elements of Badain Jaran Desert such as precipitation, evaporation, lakes and groundwater levels and temperature since2010had been obtained through located observation, based which the lake water balance, the temporal and spatial variation of the lakes and shallow groundwater levels had been analyzed. The results showed that the local precipitation cannot balance the evaporation, and the desert lakes and groundwater levels were rising fast as there was only little rainfall in winter. The levels kept highest in spring and lowest in summer, the trends of which were opposite to the seasonal distribution of local precipitation, which indicated that the lakes and shallow groundwater were mainly recharged by the deep groundwater and evaporation may be the key controlling factor of the water levels’undulation. The water ratio, salinity, hydrogen and oxygen stable isotopes of several profiles in Badain Jaran Desert and Tengger Desert were analyzed, the results of which showed that the local precipitation can only infiltrated into the surface sand layers for less than1meter. Additionally, it indicated that the8D and δ18O of rainfall were significantly more positive to the groundwater and the soil water in the deep sand layers. Therefore the precipitation and groundwater in Alxa Desert might have different sources. A simulated rainfall experiment was carried out in Badain Jaran Desert, and the results showed that in the condition of30mm rainfall the wetting front only reached the depth of40cm after17hours, and the infiltration was nearly to cease. All these results above proved that local rainfall cannot recharge to the lakes and shallow groundwater in Alxa Desert. According to the seasonal variation of the water levels in different regions of Badain Jaran Desert, the monitor of the desert springs’temperature and some geologic-geomorphic evidences, we conjectured that deep water originated from distant regions gush from the crushed stratum may be the main source of the lakes and phreatic water in Alxa Desert. In southeast of Badain Jaran Desert, deep groundwater might bubbled up from among the NE strike-slip fault and flood northwest to recharge to the brackish lakes and saline lakes in turn.