巴丹吉林沙漠沙山区径流与地下水补给条件

在全球高差最大的巴丹吉林沙漠沙山斜坡上发现了沙漠区罕见的因大气降水而产生的地表超渗径流,地表径流侵蚀,缓渗径流及因地下径流出露而产生的地表径流--风沙混合物理沉积与化学沉积(次生盐).根据电镜观察,能谱分析,化学分析和粒度分析等资料,研究了径流化学沉积物的矿物和化学组成,风积沙和径流--风沙混合物理沉积物的粒度组成,径流类型及沙山区水分平衡,降水对地下水与湖水的补给机制.超渗径流的出现表明,虽然该区降水量少,但存在能够为地下水提供补给来源的较强有效降雨过程.径流,径流--风沙混合物理沉积和化学沉积等六项科学指标从深层次上充分证明,该区降水通过入渗至少达到了沙山的下部,完全能够对地下水构成有效补给.细粒层相对的隔水性是该区地下径流出露于地表的原因.沙山区确实存在令人惊奇的水分正平衡,即在大气降水在经过蒸发和蒸腾等消耗之后,每年还有约134648.4 t/km²水补给了地下水和湖水,成为湖水的重要补给来源之一.沙山区能够产生有效降水,植被稀少蒸腾量少,沙层入渗率高和沙层受蒸发影响深度很小是该区水分出现正平衡和大气降水能够补给地下水的四个条件,也是导致该沙漠区有众多湖泊发育的主要条件.

Runoff and groundwater recharge conditions in the megadune area of Badain Jaran Desert

Field investigation was carried out in the Badain Jaran Desert, where develop numerous megadunes with the largest height difference in the world. Infiltration-excess runoff, slow seepage runoff, erosion features of runoff caused by atmospheric precipitation, as well as mixed physical sediment of runoff-aeolian sand and chemical deposition (secondary salts) caused by ground runoff converted into surface runoff, were discovered in the slope surfaces of megadunes. These natural features are rare in arid desert area. According to the data of electron microscopy observation, energy spectrum analysis, chemical analysis and particle-size analysis and others, some issues are discussed, namely, mineral and chemical composition of secondary salts, particle-size composition of aeolian sand and mixed physical sediment of runoff-aeolian sand, runoff type, water balance of megadune area and mechanism of precipitation recharging groundwater and lake water. The emergence of infiltration-excess runoff means that the strong effective precipitation can be used as a source of groundwater, although there is less rainfall in this region. Various runoff and runoff depositions on a deep level sufficiently prove that precipitation via infiltration reaches the bottom of megadune and constitutes effective recharge to groundwater. The fine layer with relative impermeability is the reason why underground runoff is exposed to Earth's surface. The positive water balance is surprising in the megadune area. Precipitation, after evaporation and transpiration, and other consumption, could provide about 134648.4 tons of water per square kilometer per year to recharge groundwater and lake water, which has become one of the important recharge sources of lake water. Positive water balance and precipitation can recharge groundwater in the megadune area and mainly depend on four conditions, namely, the presence of effective precipitation, scarce vegetation and less transpiration, a high infiltration rate and a small evaporation depth of sand layer. These factors are also the priority for numerous lakes developed in the megadune area of the Badain Jaran Desert.