高寒资料匮乏河源区地表特征性要素影响的水文过程研究

Due to severe environment, the alpine river basin is lack of data. Besides that, hydrological processes are also affected by the alpine surface characteristic elements, which include glacier, seasonal frozen soil and snow cover. Therefore, the mechanism of hydrological processes is still need more research. Hydrological processes affected by the alpine surface characteristic elements at the headwater region of the Yangtze River will be studied in this project. It is focus on effect mechanism of the glacier melt runoff process and the soil evaporation process. Field observations, stable isotope and remote sensing technologies will be used. It is mainly included: 1. Based on the consideration of surface spatial heterogeneity, soil moisture will be up-scaled from the monitoring site scale to the catchment area scale. The up-scaled soil moisture data will be validated by remote sensing retrieval soil moisture. 2. Analyses for temporal and spatial characters of soil frozen and thaw processes at the permafrost region. Impacts of that on runoff will be also analyzed. Besides that, effects of seasonal snow cover on runoff will also be analyzed by remote sensing and observed datasets. 3. Based on the application of stable isotope in runoff separation and evaporation, glacier melt runoff will be separated from total runoff for both monthly and daily time scales. Then, impacts of air temperature and glacier area on glacier melt runoff will be analyzed. 4. Contribution of glacier, seasonal frozen soil and snow cover to total runoff will be quantified at the studied catchment. According to the hydrological budget balance, runoff generation will be simulated and routed to the outlet of the studied catchment. Besides that, the soil evaporation will be also simulated. The effect mechanism of the soil evaporation process will be investigated. This study is useful to the investigation of hydrological processes at the alpine regions. It is also helpful to reveal water resources formation mechanism of the cryosphere. It is valuable for theoretical research of eco-environmental evolvement in which water plays an important role, at the alpine regions.

高寒流域观测资料匮乏，且受冰川、冻土与积雪等地表特征性要素的综合影响，其水文过程机制更为复杂，亟需深入研究。本申请以长江河源区为研究区，借助野外观测、稳定同位素及遥感等手段，开展高寒流域地表特征性要素影响下的水文过程研究，着重分析冰川融水与土壤蒸发过程的影响机制。主要包括：1、在考虑下垫面异质性的基础上，将监测点的土壤含水量升尺度至流域尺度，并对其进行验证；2、分析季节性冻土区土壤冻结与融化的时空变化特征，及其对径流的影响；结合遥感和观测数据，分析季节性积雪对径流的影响；3、利用稳定同位素技术，进行不同时间尺度的冰川融水径流分割，研究冰川融水径流过程及其影响机制；4、量化冰川、季节性冻土与积雪对径流的贡献，并进行流域土壤蒸发与产汇流过程模拟及其影响机制分析。本研究将有助于对高寒地区水文过程的深入了解，揭示冰冻圈水资源形成机理，对于水资源在高寒地区生态环境演化中的作用等理论研究具有重要价值。

高原冰冻圈生态系统对全球变化和人类干预响应十分敏感，深入开展高原冰冻圈水文过程的影响机制研究，具有重要的科学意义及社会价值。本项目立足于野外观测，借助遥感和稳定同位素等技术手段，开展沱沱河流域地表特征性要素影响的水文过程研究，主要包括流域下垫面土壤含水量遥感反演及基于水文过程反演的流域实际蒸散发量模拟与评价两个方面。研究中，改进了地表土壤含水量反演方法─地表温度与植被指数（Ts/VI）方法，使其更适用于高寒山区流域，并通过了实地观测数据的验证；提出了一种从Ts/VI特征空间确定干边与湿边的半自动提取方法，该方法可以剔除Ts/VI散点图中的异常点，提高反演精度；基于遥感反演的流域下垫面土壤湿度空间分布及其与实测土壤含水量之间的线性拟合关系式，模拟了流域下垫面平均土壤含水量序列。结果表明在考虑海拔高度和冻土影响条件下，遥感反演土壤含水量与实测值之间线性R2值达到了0.617。基于土壤含水量、降水和径流等水文要素的定点连续观测序列数据，提出了一种使用水文过程反演方法的流域实际蒸散发量(AET)模拟方法，在冰川融水径流和下垫面平均土壤含水量序列模拟基础上，模拟了沱沱河流域实际蒸散发序列，并评价了常用的实际蒸散发气象方法。其中，构建了土壤水分约束条件下沱沱河流域AET与潜在蒸散发量之间的非线性关系式，评价结果显示，该非线性关系式能够较准确的计算月尺度和两周尺度的AET序列，相应的纳西效率系数值分别为0.903和0.613；潜在蒸散发量和土壤水分约束的降水指数都可由气象数据计算得到，因此，仅使用气象数据即可实现AET的估算。蒸发互补理论模型能够准确估算月尺度的AET序列，但对较短时间尺度的AET模拟效果较差。总体而言，土壤水分约束条件下非线性关系式模拟效果优于蒸发互补理论模型。基于水文过程反演的AET模拟方法充分利用了土壤含水量等水文要素观测序列，在全球范围内越来越多的流域中开展了含土壤含水量等水文要素观测的前提下，该方法具有一定的应用前景。