中文摘要：

在典型极干旱气候条件下，在敦煌莫高窟窟顶戈壁上搭建封闭塑料拱棚，经235d的膜面凝结水分的持续抽取和土壤水分监测表明：在潜水埋深200m以下的极干旱区，有2．1g·m^-2·d^-1的水分向上运转与输出；在长期的水分输出后，土壤湿度不但没有下降，反而上升，明显高于初始湿度和对照；棚内外土壤空气相对湿度、绝对湿度和温度的监测发现，存在水分向上连续运转的条件和机制，可排除水分来自外部土壤和大气侧入的可能。由此判定，在埋深较深的极干旱地区存在潜水蒸发，潜水是土壤水分的重要来源，并通过土壤的“呼吸”与大气保持着交流。土壤盐分对土壤水分的运转和时空异质分布有重要影响。极干旱气候、地热和上层土壤的温度变化是引起GSPAC水分运转和潜水蒸发的根本原因。

英文摘要：

In typically and extremely dry climate condition, a PVC greenhouse-canopy was built on Mogao Grottoes＇ roof on a gobi. After 235 days＇ continuously extracting out of condensation water from the film of the greenhouse, and through monitoring soil water content, it was found that there were 2.1 g·m^-2·d^-1 groundwater being moved up and exported from the greenhouse soil in the extreme dry area where groundwater was more than 200 m deep. After long-term exporting water, the soil water content was not getting lower, instead, it was obviousl higher than that before it being controlled and coved. From monitoring these elements, such as soil air RH, absolute humidity and temperature inside and outside the canopy, it was discovered that the condition and mechanism of groundwater continuing moving up was existed, and the possibilities of water inside the greenhouse coming from outside soil and atmosphere could be debarred. By these judgment, in the extremely dry areas where the phreatic water was buried deeply, its evaporation is existed. The phreatic water is soil moisture＇s important source. Through soil＇ s ＂respiration＂, the moisture exchanging between soil and atmosphere is kept. Soil salinity has important effects on soil moisture movement and spatio-temporal distribution of its heterogeneity. The extremely dry climate, terrestrial heat and upper soil＇s temperature change are an ultimate reason why GSPAC＇s moisture transportation and phreatic water＇s evaporation are taken place.