The Andes of southern Chile have isolated glaciers on volcanic edifices that, together with the precipitation, contribute to several important river systems in the region. The decrease in the extension of glaciers and the negative trend in precipitation will reduce the downstream water availability. Nonetheless, studies on the sensitivity of hydrological systems due to climate change focus mainly on arid and semi-arid areas of the Andes, compared to wet regions with isolated mountain glaciers. Despite the extension and hydrological importance of the Wet Andes and significant trends of decreasing flow that have affected the region for several years, studies have yet to assess the importance of its glaciers in runoff generation. Through isotopic monitoring, we estimate the contribution of glacial melt in the Allipen headwater basin of the Wet Andes (between 38°40’S and 39°S). We performed isotopic measurements of 18O and 2H on a seasonal basis during three seasons in snow, glacial melt, lagoons, groundwater, and stream flow in nested basins. Stable isotope data were analyzed in a Bayesian framework using the MixSIAR model, where spatial and temporal relationships were incorporated. The contribution of groundwater (springs) is prominent in three of the four nested basins throughout the analyzed period. In one of the basins, lagoons correspond to the main contributing source. Additionally, the contribution of glacier thaw reached up to 30% in another of the nested basins. Meanwhile, precipitation was less important in all basins. When analyzing the complete basin (without the nested basin approach), the results show the dominance of groundwater contributions as the main source, varying between 56% and 62%, followed by ponds, which vary between 13.5% and 23%. In contrast, glacier thaw varies between 11% and 18%, even though it only covers approximately 1.5% of the total basin area. These results show the variability of hydrological processes at different spatial scales and the importance of small mountain glaciers in the basins of the Wet Andes. Furthermore, the analysis of the physical variables of the basins allows for identifying the importance of the volcanic landscape in the hydrological dynamics of the region. Our results suggest that due to climate change, it is necessary to evaluate and quantify changes in flow dynamics in humid regions, especially in basins that receive significant contributions from retreating glaciers. These results will allow for the identification of new monitoring points and techniques to discriminate and quantify the contribution of different sources and the identification of areas or hydrological processes relevant in terms of conservation or integrated management.

中文翻译：

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高山冰川在湿安第斯山脉源头流域水文动力学中的作用


智利南部的安第斯山脉在火山大厦上隔离了冰川，这些冰川与降水一起促成了该地区的几个重要河流系统。冰川延伸的减少和降水的负趋势将减少下游的水资源供应。尽管如此，与孤立的山地冰川的潮湿地区相比，关于气候变化导致水文系统敏感性的研究主要集中在安第斯山脉的干旱和半干旱地区。尽管湿安第斯山脉的延伸和水文重要性，并且多年来一直影响着该地区，并且流量减少的显著趋势已经影响了该地区，但研究尚未评估其冰川在径流产生中的重要性。通过同位素监测，我们估计了湿安第斯山脉 Allipen 源头盆地（南纬 38°40 至 39°之间）冰川融化的贡献。我们在三个季节对巢盆地的雪、冰川融化、泻湖、地下水和溪流进行了 18O 和 2H 的季节性同位素测量。使用 MixSIAR 模型在贝叶斯框架中分析稳定同位素数据，其中结合了空间和时间关系。在整个分析期间，地下水（泉水）的贡献在 4 个嵌套盆地中的 3 个中表现突出。在其中一个流域中，泻湖对应于主要的贡献源。此外，冰川融化在另一个嵌套盆地中的贡献高达 30%。同时，降水在所有流域中都不太重要。在分析整个流域（没有嵌套流域方法）时，结果显示地下水贡献占主导地位，主要来源在 56% 到 62% 之间，其次是池塘，在 13.5% 到 23% 之间变化。 相比之下，冰川融化在 11% 到 18% 之间变化，尽管它只覆盖了流域总面积的 1.5% 左右。这些结果表明了不同空间尺度上水文过程的可变性以及小山地冰川在湿安第斯山脉盆地中的重要性。此外，对盆地物理变量的分析可以确定火山景观在该地区水文动力学中的重要性。我们的结果表明，由于气候变化，有必要评估和量化潮湿地区流动动力学的变化，尤其是在因冰川退缩而做出重大贡献的盆地中。这些结果将有助于确定新的监测点和技术，以区分和量化不同来源的贡献，并确定与保护或综合管理相关的区域或水文过程。