祁连山八一冰川融水汇流过程观测与模拟研究

Modeling runoff from ice-covered catchments is vital for water resource management in mountianous areas. However, the forecasts of water yield from glaciers are likely to be inaccurate, if the runoff is effectively mediated by the glacier hydrological system. Generally, the glacier hydrological system may change from a hydraulically inefficient drainage system to a hydraulically efficient network of channels, which means the need to improve the ability of the model description of the process of glacier hydrology. There exist few researches to study the evolution of glacier drainage system and glacier confluence model in China, except some short-term observational studies conducted on the Glacier No.1 at the Headwaters of Urumqi River and Hailuogou Glacier. More research is needed combining direct measurements and modeling efforts as a base for incorporating these effects in operational runoff models. The research will investigate the process of the meteorological drive surface melting, the route of supraglacial meltwater to the bed of glacier, the evolution of englacial and subglacial drainage system on the Bayi glacier in Qilian Mountains by some field observation experiments. First, A simple physical method based on the Gauckler-Manning formula will be applied to investigate meltwater channel evolution on spraglacier. Some dye tracer experiments will be conducted to investigate the evolution subglacial drainage system structure. Finally, a model will be established to investigate the seasonal changes of the glacier hydrological system and discharge on the Bayi Glacier. The research also will give some physical or empirical parameters for the conceptual runoff models, which could incorporate explicit routines to route water through the small glaciers.

评估冰川变化对山区水资源的影响，需提高模型对冰川水文过程的描述能力。冰川表面物质收支状况的改变导致冰川水力热力条件的变化，引起了冰川排水系统（冰面、冰内及冰下）的季节性变化，加大了冰川汇流模拟的难度。目前国外很少有模型会从冰川排水系统空间分布格局来考虑冰川汇流过程，而国内涉及冰川排水系统演化和冰川汇流模拟的研究也相对较少，仅在乌鲁木齐河源1号冰川和海螺沟冰川进行过观测研究。项目选取祁连山八一冰川（小型的亚大陆型冰川）作为研究对象，拟通过野外试验，对冰面和冰下融水汇流过程进行系统监测，探讨八一冰川冰面和冰下水系及河道季节演化特征，定量或半定量地给出冰川不同阶段、不同部位的汇流参数，构建包括冰川消融、冰面汇流、冰内及冰下汇流的概念性冰川水文模型，并利用不确定行/灵敏度分析方法检验模型的不确定和敏感性，最终为流域尺度各种规模冰川融水径流模型提供科学依据和参数化方案。

评估冰川变化对区域水资源变化的影响，需提高模型对冰川水文过程的描述能力。冰川消融和融水汇流是冰川水文模拟研究中两个关键的过程，但当前冰川水文模拟中较少涉及融水汇流过程的模拟。项目通过野外观测和模型模拟，系统分析冰川-大气间能量交换过程，探讨若干综合性参数对冰川消融和汇流过程模拟的影响，揭示八一冰川排水系统季节演化规律，分析河道水力状况的变化规律，构建包含冰川消融和融水汇流的概念性冰川水文模型。结果表明：（1）净辐射是冰川的主要能量来源，其次为感热通量；八月份八一冰川冰面潜热通量存在正值现象，且持续时间较长，这一特性与国内已报道多数大陆性型冰川的能量平衡特征明显不同。（2）在数值和温度转化时间点两个方面模拟冰面温度均与实测值存在很好的一致性，模拟的反照率与实测值也存在较好的关系，这一结果有助于提高冰川水文过程的模拟；能量平衡模型中常用的0℃假设在一定程度上会过高的估计冰川消融量。（3）在年际尺度上，冰面河道的空间分布位置基本保持稳定；河网的形成明显受降水的影响明显；非主干河道的下切现象不明显；强消融期，八一冰川冰面水系极发育，消融末期，大部分冰面河道消失。（4）构建的概念性冰川水文模型较好地刻画了格网上游来水量对河道汇流的影响，较好地反演了冰面河道演变规律。