冰湖对冰川融水的滞留作用及其灾害效应研究

A large amount of meltwater was retained as glacier meltwater continuously flowing into glacial lake, which resulted in lake area expanding and water volume increasing, adjusted the cycle process of melting water in glaciated area, modified the water storage and lifetime of glacial lake, and produced far-reaching effects on hydrological processes and glacial lake outburst flood (GLOF) hazards in the glaciated regions. Currently, it is urgently to be answered: What role does glacial lake play in the dynamic of the glacier melting resource? What extent does the meltwater retained by glacial lake deteriorate the breaching probability of the potentially dangerous glacial lakes? In this project, we propose a series of models to estimate lake storage for different glacial lakes classified by proglacial landforms, types of hydrologic relationships between the glacial lakes and glaciers. Furthermore, based on the glacial lake inventories and field surveyed data, the north slope of Himalayas was chosen as an experimental region for discussing the heterogeneity of glacial lake distribution and changes, estimating the retained lake water volume during 1990-2015, figuring the informatic Tupu about meltwater retention effect by computing the increment volume of glacier-fed lake, evaluating the GLOF hazards effect of retained meltwater by calculating the potential flood volume of glacial lake, analyzing the impacts of heat flow between moraine-dam and lake water by simulating permafrost degradation of moraine-dam. The proposed study will provide further knowledge of meltwater retention effect in the view of glacier melting resource dynamics and GLOF hazards in the glaciated regions.

冰湖因不断滞留冰川融水而呈现出面积扩张和水量增多的态势，这在一定程度上调整了冰川水资源的循环过程，改变了冰湖的蓄水量和蓄水周期，对寒区水文过程和冰湖溃决灾害产生深远影响。当前亟需回答：冰湖在冰川水资源的动态变化中扮演什么角色？被冰湖滞留的冰川融水在多大程度上致使冰湖溃决风险增大？项目主要基于三期冰湖编目数据和野外观测数据，从不同冰缘地貌形态、不同冰湖-冰川的水力联系类型的角度研制冰湖水量估算模型，计算冰湖的水量。在此基础上，以喜马拉雅山北坡为研究试验区，计算1990-2015被冰湖滞留的冰川融水量及其变化，绘制冰湖滞留冰川融水的信息图谱，解析冰湖滞留冰川水资源的时空异质性，定量评价冰湖对冰川融水的滞留作用，并从冰湖危险水体估算和滞留融水对坝体冻土/埋藏冰消融影响模拟等方面，剖析被冰湖滞留的冰川融水的灾害效应。项目的完成，有助于从冰湖水量变化的角度，深入认识冰川水资源的动态变化及其灾害效应。

2018-2021年，项目研究团队根据计划书安排，主要围绕冰湖水量估算模型构建、冰湖滞留冰川水资源时空异质性解析和冰湖滞水的灾害效应分析三个内容进行。项目总体进展顺利，按期完成计划书的各项任务，取得如下重要结果：（1）维护龙巴萨巴湖野外观测站运行，获得2018-2021年龙巴萨巴湖的湖盆气象（气温、降水、湿度、气压、风）、堤坝物理参数（5层地温、4层含水量、2层热通量）、湖水水温（5层）等一批珍贵的野外资料。（2）建立了基于3S技术的冰湖编目理论与方法体系，发布了亚洲高海拔地区1990-2018年冰湖编目数据集，完成冰湖分布与变化及滞留融水信息图谱；1990和2018年，高亚洲地区分别发育27205个冰湖和30121个冰湖（面积规模在0.0054-6.46km2间），总面积分别为1806.47±2.11和2080.12±2.28 km2；1990-2018年，亚洲高海拔地区面积平均增长15.2%，但变化率空间差异显著。（3）2018年亚洲高海拔地区冰湖水资源总量为52.2Gt，其中冰川补给湖水量（约41.6Gt）占总水量的79.7%，非冰川补给湖的水资源总量约为10.6Gt（20.3%）。亚洲高海拔地区冰湖水资源分布存在明显的空间差异，其中青藏高原内陆地区与喜马拉雅山东部的冰湖水储量最多，分别占区域冰湖总水量的17.4%（9.1Gt）和15.5%（8.1Gt），Hissar Alay地区的冰湖水储量仅占区域冰湖总水量的0.4%（0.22Gt）。（4）冰川接触型湖泊扩张加速冰川的退缩速度，但冰川-冰湖耦合变化在时空上表现出显著的差异性；气候变化是冰川-冰湖耦合变化的主控因子，局部的地形因素使冰川-冰湖变化呈现复杂化趋势，而冰川物理性质差异进一步加剧了趋势的复杂性。（5）在过去60年中，典型高危险性冰湖龙巴萨巴湖湖水量以0.0132±0.0018km3a-1的速度扩张，坝体最大融化深度增大、最大冻结深度减少，坝体活动层平均以0.047m-1的速度增加，坝体稳定性下降，未来坝体溃决风险在增大。目前已发表相关资助标注的SCI论文6篇、EI论文2篇、中文核心论文9篇；发布数据集6个，其中高亚洲冰湖编目数据集申请下载量已近2万次。项目的完成，有助于从冰湖水量变化的角度深入认识冰川水资源动态变化及其灾害效应。