巴丹吉林沙漠沙山区高含量薄膜水与水分平衡研究

通过野外实地考察和实验分析,在巴丹吉林沙漠的呼和吉林湖东沙山、呼和吉林湖西沙山和伊利克敖包沙山斜坡上发现了高含量薄膜水和带状分布的灌木植被。分析表明：① 沙山沙层中出现了含量在3％~5％之间、占据厚度为0.5~3.0 m之间的高含量薄膜水,并出现了一部分水分含量大于5％的重力水,这在极端干旱的沙山斜坡沙层中是非常少见的。② 沙层中的含水量垂向分布与重力水的存在指示,在当年雨季末期,大气降水就完全能够通过沙层入渗达到2~4 m或更大深度,从而避免了蒸发作用的消耗,确保了沙层水分能够通过入渗向深层运移。③ 沙山沙层中高含量薄膜水和重力水的存在以及灌木植被带的发育充分证明,该区大气降水在经过蒸发与蒸腾消耗之后,仍有剩余的水分渗入地下,显示了沙山区沙层水分为明显的正平衡。高含量薄膜水的存在和带状植被的发育的表明大气降水至少是该区地下水和湖水的重要补给来源之一。④ 沙山表层1~4 m深度范围有时存在含量大于5%的重力水,表明沙山表层水分运移动力很强。沙层入渗率高,沙层水受蒸发影响的深度小,利于大气降水向地下水的转化,这也是该区大气降水能够补给地下水的重要原因。

Film Moisture with High Content in Sand Layer and Its Movement in Mega-dune of the Badain Jaran Desert

Through field investigations and experimental analysis, film moisture with high content and zonal distribution of vegetation were discovered on the slope of megadunes of eastern Huhejilin lake, western Huhejilin lake and Yilikeaobao megadune in the Badain Jaran Desert. The experimental results show that the sand layer has appeared film moisture with high content from 3% to 5% and with about 0.5-3 m a thick, even appeared the gravity water with a content above 5% in a small part of sand layers, which in extreme arid desert area is rare in sand layer on slope of mega-dune. The vertical distribution of moisture content and the presence of gravity water indicate that, at the end of rainy season, precipitation infiltration will be able to reach through the sand layer about 2-4 m at least or more than that, thus avoiding the evaporation effect, to ensure that the sand layer water can reach to deep megadune through infiltration. The existence of the film moisture with high content, gravity water in sand layer and zonal distribution of vegetation prove sufficiently that there are still remaining water infiltrations into underground after evaporation and transpiration, which shows that the water in sand layer of the megadune area is a significant positive balance. The film moisture with high content in sand layer and zonal distribution of vegetation indicates that precipitation is at least an important supply source of groundwater and lake water. The water film pressure difference between film water with high content and film water with low content in adjacent underlying sand layer is the driving force of atmospheric precipitation infiltration into groundwater. Content and distributive thickness of film water with high content indicate that and its migration force is stronger and can effectively supply the groundwater in this area. Sometimes there is gravity water with content of more than 5% in 1-4 m deep in the surface layer of megadune, indicating that migration force is very strong in the surface layer of the megadune. The rainy season is the supply period of sand layer water. Rapid infiltration and small depth affected by evaporating in sand layers are beneficial to the conversion of precipitation to groundwater, which also is an important reason for the precipitation can supply groundwater.