Multi-scale temporal variability in meltwater contributions in a tropical glacierized watershed
Multi-scale temporal variability in meltwater contributions in a tropical glacierized watershed
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DOI：
10.5194/hess-23-405-2019
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发表时间：
2019-01
影响因子：
6.3
通讯作者：
L. Saberi;R. McLaughlin;G. Ng;Jeff La Frenierre;A. Wickert;M. Baraer;W. Zhi;Li Li-Li;B. Mark
中科院分区：
文献类型：
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作者：
L. Saberi;R. McLaughlin;G. Ng;Jeff La Frenierre;A. Wickert;M. Baraer;W. Zhi;Li Li-Li;B. Mark
抽象。气候模型预测，低纬度高海拔地区的变暖将加剧，使热带冰川地区成为世界上最脆弱的水文系统。观察显示，由于安第斯山脉的冰川消退，径流量减少，安第斯山脉拥有99%的热带冰川。然而，融水促进径流的时间尺度及其所采取的途径-表面和地下-仍然不确定，阻碍了我们预测冰川萎缩将如何影响水资源的能力。造成这种不确定性的两个主要因素是热带冰川流域水文测量的稀疏性和全年冰川融化的水文分离的复杂性。我们使用多方法的方法，采用重复水化学混合模型分析，水文气候时间序列分析和综合流域建模来应对这些挑战。这些方法中的每一种都询问了融水，地下水和河流排放之间不同的时间尺度关系。我们的研究结果挑战了普遍持有的概念模型，冰川缓冲放电的变化。相反，在厄瓜多尔钦博拉索火山的半湿润流域，冰川融化几乎驱动了流量的所有变化（模拟中皮尔逊相关系数为0. 89），冰川贡献了20%-60%或更大范围的流量，大部分（86%）通过每小时时间尺度的地表径流，而且通过渗透，每年增加近20%的地下水贡献。我们进一步发现，降雨可能会增加冰川融化的贡献，以补充冰川融化生产的时间尺度排放，可能解释为什么在温暖但干燥的厄尔尼诺条件下，在研究地点发生最小排放，这通常会增加安第斯山脉的融化。我们的研究结果警告，从孤立的测量外推：流流量和冰川融化的贡献，在热带冰川化系统可以大大改变每小时到年际的时间尺度，由于气候变化和地表到地下流动过程。
Abstract. Climate models predict amplified warming at high elevations in low latitudes, making tropical glacierized regions some of the most vulnerable hydrological systems in the world. Observations reveal decreasing streamflow due to retreating glaciers in the Andes, which hold 99 % of all tropical glaciers. However, the timescales over which meltwater contributes to streamflow and the pathways it takes – surface and subsurface – remain uncertain, hindering our ability to predict how shrinking glaciers will impact water resources. Two major contributors to this uncertainty are the sparsity of hydrologic measurements in tropical glacierized watersheds and the complication of hydrograph separation where there is year-round glacier melt. We address these challenges using a multi-method approach that employs repeat hydrochemical mixing model analysis, hydroclimatic time series analysis, and integrated watershed modeling. Each of these approaches interrogates distinct timescale relationships among meltwater, groundwater, and stream discharge. Our results challenge the commonly held conceptual model that glaciers buffer discharge variability. Instead, in a subhumid watershed on Volcán Chimborazo, Ecuador, glacier melt drives nearly all the variability in discharge (Pearson correlation coefficient of 0.89 in simulations), with glaciers contributing a broad range of 20 %–60 % or wider of discharge, mostly (86 %) through surface runoff on hourly timescales, but also through infiltration that increases annual groundwater contributions by nearly 20 %. We further found that rainfall may enhance glacier melt contributions to discharge at timescales that complement glacier melt production, possibly explaining why minimum discharge occurred at the study site during warm but dry El Niño conditions, which typically heighten melt in the Andes. Our findings caution against extrapolations from isolated measurements: stream discharge and glacier melt contributions in tropical glacierized systems can change substantially at hourly to interannual timescales, due to climatic variability and surface to subsurface flow processes.