干旱区大尺度地下水蒸发排泄机理及遥感计算方法研究

Arid and semiarid regions occupy approximately 50% of the global land surface. These regions and their environments are considered to be water limited because annual precipitation is typically less than the annual potential evapotranspiration. Although variable with respect to physiography, geology and soils, these environments are often sensitive and vulnerable because of low and highly variable precipitation, limited water resources and sparse vegetation. The environmental changes occurring over vast areas in these arid regions include land desertification, groundwater depletion, salinization and soil erosion. These environmental changes increasingly affect human societies and have a growing influence on global biogeochemical cycles. The vegetation is an environmental indicator in water-limited ecosystems and is often linked to both the causes and consequences of arid land degradation. The role of vegetation in the dynamics of soil moisture, runoff, and streamflow has been acknowledged to be very important. Understanding the influence of vegetation on hydrological changes is part of the foundational basis of ecohydrology. Therefore, studies on quantifying the relationship between the vegetation and water resources represent a critical step in developing advanced ecohydrological approaches, supporting resource management and environmental change. However, due to little population density, inconvenient transportation and shortage of available long-term monitoring data, traditional methods performing qualitative ecohydrological analysis that usually employ point observations and are only representative for local scales, cannot be extended to large areas. The use of remote sensing can provide continuous and representative measurements of several relevant physical parameters at scales from point to continent. The purpose of this study is to develop a method to quantitatively assess the vegetation eco-hydrological process using remote sensing methods and applying it to ecohydrological applications in China. Firstly, the correction method of regional evapotranspiration(ET) which is estimated by remote sensing will be found by combination of field observations. Secondly, the quantitative relationship among groundwater depth,vegetation growth, soil type and climate will be established, and further the impact factors of surface ET will be analyzed in this research. Furthermore, the relationship between surface ET and groundwater depth will be established based on statistics. The mechanism of groundwater evaporation will be understand through the quantitative relationship between groundwater depth and evaporation intensity in this research. The result can provide scientific surport for sustainable development of water resources and eco-environmental protection in north-western China. It also has important significance in generalization and perfection of ecohydrology theory and its application.

我国西北干旱地区，缺水少雨，水资源时空分布不均匀，生态环境极为脆弱， 地下水资源在盆地人类生存和社会发展中扮演着极为重要的角色。地下水资源合理开发利用的关键是深入认识区域生态－水文过程及其演变规律。本项研究将采用定量遥感技术，结合地面蒸散发观测结果，建立大尺度遥感蒸散发计算结果的校正方法；分析植被时空分布，通过植被与地表蒸发之间的关系研究，建立地表蒸散发与植被生长、地形地貌、土壤、气候等要素间的定量关系，深入了解干旱区地面蒸散发的主要控制因素；利用统计学方法，研究干旱区地表蒸散发与地下水之间的关系，将地下水在地表蒸散发中的贡献分离出来，揭示干旱区地下水蒸发排泄的机理。研究成果将为西北干旱区水资源的合理开发与配置，以及西北地区生态环境的保护和规划提供有效的技术支持；也对完善和推广生态水文地质学理论和应用具有重要的意义。

我国西北干旱地区，缺水少雨，水资源时空分布不均匀，生态环境极为脆弱，地下水资源在盆地人类生存和社会发展中扮演着极为重要的角色。地下水资源合理开发利用的关键是深入认识区域生态-水文过程及其演变规律。本项研究以柴达木盆地为研究区，采用定量遥感技术，基于表面能量平衡系统，计算了柴达木盆地的实际蒸散发；并应用表观热惯量法，对盆地土壤湿度进行了模拟，结合土壤湿度实测结果，建立了大尺度遥感蒸散发计算结果的校正方法；应用统计学方法，讨论了地表蒸散发与植被生长、地形地貌、土壤、气候等要素间的定量关系，深入了解干旱区地面蒸散发的主要控制因素。同时，本项研究分析了柴达木盆地植被的时空分布特征，讨论了植被与地下水的相互依存关系，圈出了浅层地下水分布的可能范围。此外，本项研究还应用水体指数法，定量分析了柴达木盆地湖泊随时间的变化特征，分析了冰川消融及区域地下水位变化对湖泊面积变化的影响。研究成果将为西北干旱区水资源的合理开发与配置，以及西北地区生态环境的保护和规划提供有效的技术支持；也对完善和推广生态水文地质学理论和应用具有重要的意义。