流域下垫面植被、地形、土壤等因素对径流的调控机理

Runoff is impacted by precipitation (substance), potential evapotranspiration (energy), and system characteristics (Underlying Surface Characteristics, USC). The relationship can be quantitatively described by Budyko or Fu's theoretical formulas. However, it remains unclear how a number of underlying surface factors of the system such as vegetation, soil, and topography related to USC, thus leading to larger controversy over the interpretation of results according to numerous studies over different regions of interest, especially the impact of vegetation, slope, the area of watershed etc. on runoff. We suppose that an important reason could be different contributing rates of underlying surface variables to USC, apart from differences of precipitation and potential evapotranspiration. This project aims to find out the quantitative relationship between USC and underlying surface variables, then further explain the mechanism of their effect on runoff, which is of vital importance to understand how the different underlying surface changes affect the water distribution and yield in different climate conditions. We select three different study areas regarding different spatial scales — typical watersheds worldwide from a global scale, Dongjiang River and Beijiang River basin as regional scale, and point-scale catchments and Open Top Chamber (OTC) platform in Dinghu Mountain. Based on the long-term observations of meteorological and hydrological data, soil data, and land use/land cover data, combined with theoretical model calculations on partitioning the effect of precipitation, potential evapotranspiration, and USC on runoff, this project is expected to achieve a quantitative investigation of different underlying surface variables on the USC and its effect on runoff. The study will provide valuable information for decision-making with respect to selecting the appropriate measures on land use and cover change for better water resources management in different climate zones, and serve for the harmonious development between human and nature.

径流受降水（物质）、蒸散潜力（能量）和系统特征（下垫面特征,USC）的影响，它们的关系可由布德科或傅抱璞等公式定量描述。然而USC是如何由植被、地形、土壤等因素表征的并不清楚，导致全球众多研究者对观测到的植被、坡度、流域面积等影响径流量的阐释差异较大。我们认为除了降水和蒸散潜力的差别外，一个重要原因是下垫面众多因素对USC的贡献率不同造成的。本项目旨在弄清下垫面各因素与USC的关系，进而探明它们对径流的影响机理，寻求解答争议的内在规律。实验从3个层面选取研究区域，一是覆盖全球的典型流域、二是个案水平的东江流域和北江流域、三是精细水平的鼎湖山径流场和开顶箱实验平台。基于长期监测的气象、水文、土壤、土地利用和覆盖等空间属性数据，结合区分降水、蒸散潜力和系统特征的计算，定量探索下垫面因素对径流的影响机理。该研究将为不同气候区域选择适合水资源管理的下垫面措施提供决策依据，服务人与自然协调发展。

径流受降水（物质）、蒸散潜力（能量）和系统特征（下垫面特征,USC）的影响，它们的关系可由布德科或傅抱璞等公式定量描述。然而USC是如何由植被、地形、土壤等因素表征的并不清楚，导致全球众多研究者对观测到的植被、坡度、流域面积等影响径流量的阐释差异较大。本项目以长期定位观测、遥感解译和理论模型为手段，定量分析流域下垫面特征的时空格局与敏感性，推理确定了气候变化和下垫面特征参数的临界值及相应的水文敏感性；深入揭示下垫面变化对蒸散发和径流的调控机制，明晰了下垫面变化相对于气候变化对产水量的贡献量问题；同时基于Budyko理论框架发现蒸散发比率（AET/P）对干旱指数（PET/P）的敏感性会随着干旱程度上升而下降，但这种下降趋势同时会因应流域下垫面特征的差异而不同。本项目的研究结果将为不同气候区域选择适合水资源管理的下垫面措施提供决策依据，服务人与自然协调发展。