变化环境下的雅鲁藏布江流域径流响应与水文过程演变机理研究

Response of runoff and evolution mechanism of hydrological cycle under the driving of climate change has being a very important field of research in hydrological sciences, and also one of the key scientific questions for the international research plan initiated by the International Association of Hydrological Sciences (IAHS). In the present research project proposed, the Yarlung Zangbo River basin was selected as the study area. With the combination of observed gauging data, remote sensing and radar data as well as the statistical downscaling output, a multi-source data assimilation technique will be developed to use for the simulation of hydrological processes in ungauged basins. The characteristics of runoff evolution will be investigated, the key factors to influence runoff will be identified, and the source of runoff recharge and its spatial and temporal distribution characteristics will be analyzed in the study area. On the basis of multi-sources remote sensing images, the evolution of underlying conditions will be analyzed, the ecosystem model will be developed, and dynamic evolution mechanism of vegetation ecosystem will be explored. On the basis of field observed data, the mechanism of runoff generation and concentration in typical basins of the Yarlung Zangbo River basin in a very cold region with complex underlying conditions will be clarified. The distributed eco-hydrological model with snowmelt runoff and frozen soil module will be developed, and bidirectional coupling between hydrological processes and vegetation ecosystem will be formulated. The evolution of hydrological processes and ecological system will be analyzed in the Yarlung Zangbo River basin. Response of runoff and evolution mechanism of hydrological cycle in the study area under changing environment will be revealed. The results of this study will provide theoretic basis and scientific support for the water resource management and ecological restoration in the Tibet Autonomous Region.

气候变化驱动下的径流响应与流域水循环演变机理是水文科学研究的热点问题，也是国际水文科学协会（IAHS）倡导的国际研究计划核心科学问题之一。本项目拟以雅鲁藏布江流域为研究对象，结合地面观测数据、遥感遥测资料和统计降尺度输出结果，研究多源数据融合技术，解决缺资料流域水文模拟的技术难题。分析研究区径流演变特征，辨识径流演变关键影响因子，揭示径流补给来源及其时空分布特征。基于多源遥感数据，分析研究区下垫面演变规律，构建陆地生态系统模型，揭示植被生态系统动态演变机理。结合野外试验观测数据，研究雅鲁藏布江典型流域高寒地区复杂下垫面条件下的产汇流机理，构建考虑融雪径流和冻土的分布式生态水文模型，实现水循环过程和植被动态过程的双向耦合，辨析雅鲁藏布江流域水文过程和生态过程演变规律，揭示变化环境下雅鲁藏布江流域径流响应与水文过程演变机理，为西藏地区水资源管理、生态恢复等一系列重大问题提供理论依据和科技支撑。

气候变化影响下的水循环与水资源演变规律研究是国际地圈生物圈计划、世界气候研究计划和全球环境变化国际人文因素计划等重大科学计划的前沿科学问题之一，也是国际社会普遍关注的全球性问题和各国政府的重要议题之一。我国西南河流源区生态环境极为脆弱，开展该类地区水循环与水资源对气候变化和人类活动的响应研究具有十分重要的现实意义。项目以雅鲁藏布江流域作为研究对象，围绕“气候和下垫面协同变化的径流效应”的关键科学问题，开展了流域气候变化-径流演变互馈机理辨识、流域下垫面植被动态演变机理及其驱动力分析以及气候变化驱动下的流域水文过程响应研究，系统分析和揭示了变化环境下径流响应特性与生态水文过程演变机理。取得的重要结果和关键数据包括：.（1）开展了流域基础数据的收集、制备及评估工作，揭示了雅鲁藏布江流域气候-下垫面-径流的时空演变规律及其相关关系。得到流域土壤湿度同化数据及具有较好模拟精度的降水卫星数据。流域气温呈上升趋势，土壤水、降水和径流呈相似的年际变化特点。流域呈整体湿润化趋势。极端降水频率显著上升，引起洪涝灾害的风险在中游东部和下游南部增加。.（2）基于流域植被动态模拟，辨识了流域植被动态演变的主要驱动因子及其驱动机理。研究基于MODIS数据的LPJ植被动态模型，开展了流域陆地生态系统演变分析，识别了雅鲁藏布江干支流及不同下垫面条件子流域径流变化的驱动因子。.（3）基于流域水文过程模拟，从机理上揭示了气候与下垫面协同变化下的径流响应及其演变规律。对冻融过程进行了精细化分析，厘清了冻融时期土壤含水量变化趋势和土壤水分深度变化及其对径流深变化的贡献；对雅江冰川物质平衡序列进行了重构，分析了气候变化对其的影响；开展了流域未来气候变化情景下的水文过程模拟和分析，降水变化仍是雅江流域径流变化的主导因素。. 研究结果提高了我们在高寒流域复杂下垫面影响下的产汇流机理的认识，极大地推动了雅鲁藏布江水科学基础理论的研究。