天山北坡不同冰川覆盖率流域径流组成及变化研究

The northern slope of Tianshan Mountains is the priority areaof the new roundofgrand western development program, and a “core area” on theSilk Road Economic Belt. The water shortageis the greatest threat to thesustainable development of socioeconomic and ecological system in the northern slope of Tianshan Mountains, where the water resources derived from snow and glacier melt are more vulnerable and sensitive to climate change. The lack of understanding about runoff composition and its changes are the main sources of uncertain in the assessing the regional hydrological impacts of climate change. This project will focus on the runoff composition and change in different glacierized catchments on the northern slope of Tianshan Mountains. Through intensified precipitation and glacier observations and multi-source remote sensing data, we will reveal the spatial distribution characteristics and change rule of precipitation, and build the model precipitation forcing data and glacier/snow calibrating and validating data. After further improvement and perfection of glacier melt and dynamic schemes in the VIC-CAS model based on the observations and experiments of typical glaciers, a hydrological model that suits for the special characteristics of runoff yield and concentration in Tianshan Mountains can be built. Based on the hydrological simulation method, this project quantitatively depicts the runoff components, change mechanisms, future change trends and these differences for different glacierized catchments on the northern slope of Tianshan Mountains. The project will lay a scientific basis for the water resource management and the construction of Silk Road Economic Belt.

天山北坡是国家新一轮西部大开发的重点区域之一，也是“丝绸之路经济带”的核心区域，水资源匮乏是制约该区域社会经济和生态系统可持续发展的关键问题。在全球变暖背景下，以冰雪融水补给为基础的天山北坡水资源系统更脆弱和敏感。针对该区流域径流组成及其变化认识的欠缺、制约着山区水资源变化准确评估的现实，本项目拟以天山北坡不同冰川覆盖率流域为研究对象，通过地面加强的降水和冰川观测结合多卫星遥感手段，确定降水分布及变化规律，获取冰川面积和物质平衡及积雪变化数据，从而建立模型降水驱动和冰川/积雪校正和验证数据集；基于典型冰川的观测和实验，对已发展的VIC-CAS模型的冰川消融及动态变化方案进一步改进和完善，从而构建适合天山山区流域产汇流特点的水文模型；通过数值模拟，系统研究天山北坡不同冰川覆盖率流域的径流组成、变化机理、未来变化趋势及其差异性，为合理的水资源规划提供科学依据，服务于“国家丝绸之路经济带”建设。

水资源缺乏是制约天山北坡区域社会经济和生态系统可持续发展的关键问题，在全球变暖背景下，以冰雪融水补给为基础的天山北坡水资源系统更为脆弱和敏感，亟需定量评估天山北坡流域的径流组成、变化机理及未来趋势。围绕项目的总体目标，在降雪与积雪对气候变化的响应机理、水文模型的优化与改进、冰冻圈流域水文预估方面取得一定的进展，完成了项目预定目标。项目主要进展包括：1）发展了一个包含单条冰川消融及动态变化方案、融雪水追踪方案及水库水量调节方案的VIC-CAS水文模型，该模型已成为国家重大基础建设的基础计算平台。2）系统评估西北干旱区降雪的时空特征及趋势，指出“高温”极端降雪事件是导致降雪增加的主要原因，这一趋势将持续到本世纪中期。3）提出了利用遥感的冰川面积变化数据结合观测的径流来校验模型，减小了冰川流域水文模拟和预估的不确定性；在此基础上，定量解析了天山北坡6个不同冰川覆盖率的径流组成、变化机理及未来趋势，指出由于冰雪融水的减少，天山北坡暖季（5-8月）的径流将大幅下降，水安全将面临巨大的威胁；将发展的VIC-CAS推广到了青藏高原流域，发现由于降雨径流的增加，青藏高原腹地的大江、大河源区的河川径流将呈现增加趋势，而祁连山的内陆河流域，由于冰冻圈的萎缩，夏季河川将显著下降。4）梳理了已有冰冻圈水文方面的研究进展，系统总结了中国冰冻圈融水径流历史及未来变化特点，指出在温升2 ℃阈值下，到21世纪末，西北干旱区冰川融水量将减少34% ~ 74%，其将导致水源涵养能力下降、径流补给量减少、对水资源的调节作用减弱、流域径流变化幅度增加、发生旱涝的风险增加、春汛提前等。