基于流量监测的西藏东南部然乌湖水量平衡季节变化及其补给过程分析

青藏高原分布着亚洲大陆最大的湖泊群,其湖泊变化对气候变化响应敏感。基于遥感数据的湖泊面积变化不足以反映外流湖对气候变化的响应,需借助湖泊水量平衡过程分析来进一步研究各补给要素的变化。本文利用2015年4月-11月然乌湖水文气象监测数据,通过建立流量—水位关系,依据连续的水位数据重建了观测期内然乌湖主要径流的水文过程线,并结合SRM模型分析了然乌湖的水量平衡过程及季节变化。结果表明,观测期内然乌湖入湖水量约为18.49×10⁸ m³,其中冰川融水约为10.06×10⁸ m³,冰川融水占然乌湖补给的54%以上,湖面降水、湖面蒸发对湖泊水量平衡过程影响微弱。流域降水对湖泊的补给具有明显的季节特征。春季受西风南支扰动影响,然乌湖地区降水量大,降水是春季然乌湖的主要补给源。夏季和早秋由于气温升高,冰川消融量大,冰川融水是湖泊补给的主控因素。在未来气候变暖的条件下,冰川融水将会在湖泊补给中占据更大比例,并可能使得流域内的冰湖水量增加,产生潜在灾害风险。

Seasonal variations of water balance and supply process based upon discharge monitoring in Ranwu Lake of Southeast Tibet

The Tibetan Plateau boasts the greatest lake group in the Asian continent, where the lakes respond sensitively to climate change. For the exorheic lakes, the area changes based on remote sensing data are insufficient to reflect their responses to climatic changes. Water balance analyses of these lakes are needed for understanding the hydrological processes of lake basins and their relationships with climate changes. In this paper, we use the hydrological and meteorological monitoring data in the Ranwu Lake Basin from April to November in 2015 to examine the relationship between water level and runoff and reconstruct flux process line according to continuous water level data. Together with the snowmelt runoff model (SRM) simulation, we analyze the water balance process and its seasonal changes of the Ranwu Lake. The result shows that the total water yield inputted into the lake during the monitoring period is about 18.49×10⁸ m3, and that the glacial melt water is about 10.06 ×10⁸ m3, accounting for more than 54% of the lakes' supplies. Precipitation and evaporation of lake water surface and the lake water storage change have only slight effects on the process of lake water balance. Replenishment of the lake water is clearly seasonal as it depends on rainfall. Under the influence of southern branch of Westerlies, the Ranwu Lake area witnesses high precipitation, which is the main supply source in spring. Due to temperature rise in dummer and early autumn, a large amount of glacial melt water is a dominant factor of the water balance of this lake. With the temperature rise in the future, glacial melt water will occupy higher proportions in the total supplies of the lakes in this area. It will conduce to the speedy rise of the glacial lake level and lead to potential hazard risks.