希夏邦马峰北麓佩枯错流域入湖河流补给水文过程研究

Replenishment composition and change of inflowing rivers is one of important factors for the inland lake evolution in the Tibetan Plateau under the condition of climate change. This study is carried out in the Peiku Co Basin located at the northern foot of Mt. Shishapangma, which is a typical inland lake in the Tibetan Plateau. Based on field observations, integrating melting runoff model, hydrogen and oxygen stable isotopic, and remote sensing, this study is focus on hydrological recharge processes of inflowing rivers of the lake. Supported by continuous field observation and sampling, with the method of hydrogen and oxygen stable isotope separation, each contribution from glacier and snow melting, and precipitation is quantified. Based on monthly data of glacier and snow area obtained by remote sensing interpretation, the sequences of meting runoff from glacier and snow are calculated through improving degree-day model. The long-term series of inflow runoff is recovered by applying methods such as runoff coefficient calculation, area analogy, and runoff overlay. Finally, the impact of variation of glacier and snow melting runoff to the lake is determined. This application can enrich the basic researches on hydrological processes for the un-gauged inland lake basin in the Tibetan Plateau. Meanwhile, this study has important theoretical and practical significances for deeping the researches of inland lake change processes such as expansion, shrink, and even breaking, scientifically understanding the effect of hydrological processes to the formation and evolution of alpine-cold inland lake ecosystems.

气候变化背景下入湖河流补给构成及变化是导致青藏高原内陆湖泊演变的重要因素。本研究选取希夏邦马峰北麓佩枯错流域为研究区，立足野外观测，结合融水径流模型、氢氧稳定同位素与遥感等技术，开展冰川、积雪融水与流域降水对入湖河流补给的水文过程研究。在野外连续观测及采样数据支持下，应用氢氧稳定同位素径流分割方法，量化冰川、积雪融水及降水对河川径流的贡献；基于遥感解译获取的月尺度冰川与积雪面积序列，改进度日模型，建立冰川与积雪融水径流序列；采用径流系数、面积类比与径流叠加等方法，构建入湖径流长序列数据；分析气候变化背景下流域冰川、积雪融水径流变化对湖泊的影响。本申请可极大地丰富青藏高原资料匮乏区内陆湖泊流域水文过程基础研究积累，对于深化高寒内陆湖泊扩张、退缩甚至溃决等演变过程研究，科学认识水文过程在高寒湖泊流域生态环境形成及演化中的作用，以及流域防灾减灾等具有重要的理论价值和实践意义。

气候变化背景下入湖河流补给构成及变化是导致青藏高原内陆湖泊演变的重要因素。本项目基于野外考察及观测等手段，借助遥感与GIS技术，在希夏邦马峰北麓佩枯错流域开展冰川、积雪融水与降水对入湖河流补给的水文过程研究。通过对流域气象及主要入湖河流水位、流量的连续观测，构建了佩枯错流域1970-2017年入湖径流序列资料；基于多源遥感数据，包括Landsat影像与MOD10A2积雪产品，采用度日模型方法，识别了冰川与积雪覆被及其融水径流的动态变化，并结合降水观测数据，分析了入湖径流补给构成及变化特征；利用ICESat和Cryosat-2测高数据计算了湖泊储水量，并阐述了气候变化背景下入湖径流对佩枯错湖泊储水量变化的影响机制。研究结果表明，1976-2010年间佩枯错流域冰川呈退缩趋势，冰川面积共减少60.57 km2，相对1976年的变化率为39.58%，变化速率为-1.73 km2/a，冰川储量共减少17.57 km3，相当于冰川水资源158.14亿m3，减少比例近50%；2000-2018年间流域冰川融水总量为2.36×109 m3，积雪融水总量为3.92×109m3，并受气候变化影响，冰川与积雪融水量分别以0.55×107 m3/a和0.29×107 m3/a的速率增加。降水是入湖径流的最主要来源，其次为冰川融水和积雪融水，三者的贡献率分别为55.6%、27.7%和16.7%。2000-2018年间暖干的气候变化趋势导致了湖泊呈萎缩趋势，湖泊水位平均以-0.02 m/a的速率持续下降，储水量以-0.27×108 m3/a的速率共减少4.85×108 m3。本研究结果对科学认识喜马拉雅山脉中部地区冰雪融水对水循环过程的影响具有重要意义。