水分是引起莫高窟文物病害的关键因子，水-盐耦合导致了酥碱、起甲、空鼓、霉变等众多病害的发生，但洞窟内水分来源与引发水分运移的动力基础尚不明确，水分来源与活动规律的不确定性给壁画病害的防治带来了很大困难。拱棚-凝结实验表明窟顶戈壁存在潜水蒸发，环境对潜水蒸发有重要影响，其中太阳辐射是引起潜水蒸发的主要动力基础。对于完全规避了太阳辐射的洞窟来说，是否存在潜水蒸发尚无确切的证据。本项目将窟顶戈壁水分研究中较为成熟的凝结法应用到典型洞窟中，利用冷凝收集封闭洞窟内的蒸发水分，通过蒸发数量、蒸发特征及水分同位素特性确定洞窟水分来源与驱动基础。同时，洞窟内收集水分过程也是对洞窟温湿度进行调控的过程，应用除湿空调设备对洞窟微环境的控制，分析洞窟内的温湿度变化及窟外天气过程对洞窟水分蒸发的影响，揭示洞窟水分活动机理，为壁画病害的主动预防提供科学依据，为莫高窟文物的保存及保护提供新的思路与方法。

Water is a key factor in causing cultural relics deterioration at Mogao Grottoes. Water-salt coupling leads to such deteriorations as disruption, flake, detachment and mildew. But it is uncertain to find cave water sources and dynamical foundation of moisture transport, which brings enormous difficulty for us to control diseases of wall paintings. Arch shed-Condensation test manifests phreatic water evaporation exists in the Gobi Desert on top of Grotto cliff body and the environment has a main influence on phreatic water evaporation. Where in solar radiation is the major factor to result in water evaporation. To caves there without any solar radiation, no evidence of water evaporation has been found. This project applied Condensation, a relatively mature method among the research of cliff top water to typical caves. This method made use of condensing to collect evaporate water from closed caves and identified cave water sources and driving force by evaporation quantity, evaporation characteristics and water isotope characteristics. Meanwhile the process of collecting moisture in the cave was a way to regulate temperature and humidity, in the process using desiccant air conditioning system to control micro-climate and analyzing changes of humidity and temperature in the cave and the influence of outside weather to moisture evaporation inside, and then finding water activity mechanism to provide the scientific basis of initiative preventing mural deteriorations and new thoughts and methods to prolong the lifetime of cultural relics of Mogao Grottoes at the same time.