气候变化驱动下黄河源区冻土退化过程及其对坡面径流的影响机制

The change of frozen soil will significantly affect the change of underlying surface in cold regions under the influence of climate change. Especially, permafrost degradation affects the physical, chemical and biological process of the ecological and hydrological system in cold regions. Hydrological process of the frozen soil is the important carrier or main form of matter migration and energy transformation among each surface layer of cold regions. So the hydrological process of frozen soil is one of the main driving forces to water-resources deterioration and ecological-function degradation. In Qinghai-Tibet Plateau, the permafrost occurrence is complex due to different terrain feature. Therefore, the different frozen-soil degradation ways differently affect the watershed runoff process. This has been increasingly important to reveal the multiple influence mechanism of the different degradation-process of frozen-soil on runoff. Thus, this study selects "one sunny slope and one shady slope" of two field profile as the classic investigated example in the source region of Yellow River. And this study also builds the hill-slope observation test-field of frozen-soil, runoff and hydrology based on "point-line-surface" principle. According to the field observation data, we clarify the degradation process and way of the seasonal frozen-soil and the permafrost under the influence of climate change. We also study the change characteristics of the hill-slope runoff process under the typical frozen-soil degradation stages. Then, we build the physical mechanism model of the permafrost hydrological process on the hill slope. And the study simulates the difference mechanisms of the hill-slope runoff process in typical stages of frozen-soil degradation by the use of the building model. So the relationship between the frozen-soil degradation and the runoff process is revealed based on the perspective of the life cycle of frozen-soil. The results enhance the cognitive ability of the formation process and evolution mechanism of the river runoff and the prediction ability of the runoff change. And it will provide theoretical basis and scientific measures for the stability and adaptability of basin water resources.

气候变化驱动下冻土的变化将会显著影响寒区下垫面的变化，进而影响寒区生态和水文系统的物理、化学和生物过程。其中冻土水文过程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地影响着流域径流过程，为深入揭示其多元机制与差异机理，立足于坡面尺度，选取“一阴坡一阳坡”两个野外典型剖面，基于“点-线-面”坡面冻土-径流-水文观测试验场，明晰气候变化驱动下季节冻土和多年冻土退化过程与方式，研究典型冻土退化阶段下坡面径流过程的变化特征，构建坡面冻土水文过程物理机制模型，模拟分析不同冻土退化对坡面径流影响的差异性和敏感性，从“冻土生命周期”角度全面揭示冻土退化与坡面径流过程之间的关系，从而提升流域径流形成演化的认知能力与径流变化的预测能力，并为流域水资源稳定和适应性利用提供理论基础与科学对策。

气候变化驱动下冻土的变化将会显著影响寒区下垫面的变化，进而影响寒区生态和水文系统的物理、化学和生物过程。为此，研究在认识气候变化驱动下黄河源区冻土不同退化过程、模式与变化趋势的基础上，拟初步阐明典型冻土退化阶段坡面径流过程的变化特征，揭示典型冻土退化阶段对径流过程的影响机理，从坡面尺度上回答气候变化驱动下黄河源区冻土退化与径流变化的关键过程、相互关系与影响机制。项目选择在康穷小坡地、汤岔玛滩地、巴颜喀拉山北坡等地新增冻土径流要素观测，形成了涵盖气象、冻土、径流等关键要素的综合坡面观测场，构建了坡面冻土径流过程野外监测体系，系列开展了冻土退化对气候变化的响应、不同冻土类型下土壤水分运移特征、冻土退化对径流过程的影响等工作，初步理解了气候变化驱动下冻土退化过程及其水文效应。研究取得如下结果：1）分析了气候变化驱动下多年冻土过去60年及未来近百年的变化过程，进一步明晰了黄河源区多年冻土退化过程、模式与方式；2）揭示了不同冻土退化阶段下坡面活动层土壤水文过程季节性运移特征，进一步明确了典型冻土退化阶段下坡面径流过程的差异性响应特征；3）模拟了不同冻土退化情景下土壤水分运移过程特征与地下水文过程特征，进一步明晰了冻土退化对坡面径流过程的影响机制与作用机制。项目通过野外监测和数值模拟进一步明晰冻土在水文过程中的作用，加强了冻土对产流的影响机制的认识，进而提升了对冻土区水文模型的预测能力，从而提升流域径流形成演化的认知能力与径流变化的预测能力，并为流域水资源稳定和适应性利用提供理论基础与科学对策。