黄河源区典型冻土退化方式对水文过程影响的时空差异及敏感预估

Permafrost degradation and its freezing-thawing process affect the physical, chemical and biological process of ecological and hydrological system in cold regions. Especially, frozen-soil water movement is the important carrier or main form of migration-transformation of matter and energy among each surface-layer of cold regions. So the frozen-soil water movement is one of the main driving forces to water-resources deterioration and ecological-function degradation. Due to the complexity of frozen-soil type in Qinghai-Tibet Plateau, different permafrost-degradation ways differently affect the hydrological-geological conditions and hydrological processes. In order to further reveal the multiple and difference mechanism between the hydrological processes, two field permafrost-hole profiles located in one sunny slope and one shady slope are investigated in the source region of Yellow River. Firstly, the investigated permafrost is divided into 3 kinds of the hillside, gentle-slope and flat-ground based on the terrain feature. Meanwhile, the permafrost-degradation process is classified into 3 stages of initial-rising, thawing-sandwich and end-disappearing. We study on the differentiation regularities of hydrologic process under different frozen-soil types and the variation characteristics hydrologic process under typical permafrost degradation stages. Then, the study simulates the differences and sensitivities of hydrologic process in typical stages of permafrost degradation under different frozen-soil types by using permafrost hydrology-process model. Moreover, the "space-time" mechanism is superimposed to different hydro-geological unit from point to surface. It will estimate the macroscopically impact on water resources changes due to the permafrost degradation in the whole source region of Yellow River. This study will completely reveal the mechanism of hydrologic process to permafrost degradation from two angles of "space-time". The results provide important parameters and theoretical basis for establishing regional permafrost-hydrology model and its accurate simulations.

冻土退化及其冻融过程影响着寒区生态和水文系统的物理、化学和生物过程。其中冻土水分运动是物质和能量在寒区地表各圈层迁移转化的重要载体与主要形式，是水资源恶化与生态功能退化的主要驱动力之一。在青藏高原黄河源区，冻土赋存状况复杂，不同冻土退化方式差别化影响着寒区水文地质条件与水文过程，为深入揭示其多元机制与差异机理，选取“一阴坡一阳坡”两个典型野外冻土钻孔剖面，基于山坡、缓坡、平地3种冻土类型和初期升温、融化夹层、末期消失3个退化阶段的认识，研究不同冻土类型下水文过程的分异规律与典型冻土退化阶段下水文过程的变化特征，运用冻土水文过程模型，模拟分析不同冻土类型在不同退化阶段下水文过程的差异性和敏感性，并将其叠加到不同水文地质单元上由点及面预估源区冻土退化对水资源变化的宏观影响，从“空间-时间”两个角度全面揭示冻土退化对水文过程的作用机制，从而为区域冻土水文模型建立与精确模拟提供重要参数与理论基础。

冻土退化及其冻融过程影响着寒区生态和水文系统的物理、化学和生物过程。其中冻土水分运动是物质和能量在寒区地表各圈层迁移转化的重要载体与主要形式，是水资源恶化与生态功能退化的主要驱动力之一。在青藏高原黄河源区，冻土赋存状况复杂，不同冻土退化方式差别化影响着寒区水文地质条件与水文过程，为深入揭示其多元机制与差异机理，在黄河源区构建了典型坡面冻土水文过程监测体系，开展了不同冻土退化阶段下的水分运移特征、典型冻土退化阶段下水文过程的差异响应、冻土退化对水文过程的影响机制等工作，初步理解了坡面尺度下冻土退化的水文影响。主要研究结果：1）建成了涵盖气象、冻土、径流等关键要素的综合坡面观测场，积累了典型坡面冻土水文过程监测数据集；2）识别了影响坡面冻土土壤水分空间异质性的主控因子及其相互作用关系，明确了不同冻融期与不同深度坡面冻土土壤水分的主要环境影响因子；3）揭示了多年冻土活动层土壤水文过程季节变异特性，明确了融化期多年冻土和季节冻土土壤水分运移过程的差异性规律；4）模拟了不同冻土退化方式下的土壤水分运移过程与地下水文过程，明晰了冻土退化对坡面水文过程的影响机制。研究成果将为深入理解流域冻土水文效应与有效推进区域生态文明建设提供科学依据与基础支撑。