Stable water isotope variation in a Central Andean watershed dominated by glacier- and snowmelt

Abstract

Central Chile is an economically important region for which water supply is dependent on snow- and ice melt. Nevertheless, the fraction of water supplied by each of those two sources remains largely unknown. This study represents the first attempt to estimate the region's water balance using stable isotopes of water in streamflow and its sources; isotopic ratios of both H and O were monitored during one year in a high-altitude basin with a relatively high glacial cover (11.5%). We found that the steep altitude gradient of the studied catchment caused a corresponding gradient in snowpack isotopic composition and that this spatial variation had a profound effect on the temporal evolution of streamflow isotopic composition during snowmelt. Glacier- and snowmelt contributions to streamflow in the studied basin were calculated using a quantitative analysis of the isotopic composition of streamflow and its sources, resulting in a glacier melt contribution of 50–80% for the unusually dry melt year of 2011/12. This suggests that in (la Niña) years with little precipitation, glacier melt is an important water source for Central Chile. Predicted decreases in glacier melt due to global warming may therefore have a negative impact on water availability in the Central Andes as well as in comparable semi-arid regions of the world; this impact is non-commensurable with areal glacial cover or with the relative areal influence coverage of glacier versus seasonal snowpack. The pronounced seasonal pattern in streamflow isotope composition and its close relation to the evolution of snow cover and to discharge presents a potentially powerful tool for relating discharge evolution in mountainous, melt-dominated catchments with related factors such as contributions of sources to streamflow and snowmelt transit times

Interannual variability in glacier contribution to runoff from a high‐elevation Andean catchment: understanding the role of debris cover in glacier hydrology

“…As demonstrated by previous studies for individual years, snowmelt is the largest contributor to runoff in Andean catchments of central Chile with an outlet point around 3,000 m asl (Ohlanders et al, ; Ragettli & Pellicciotti, ). In this study, we showed that this result holds for a long time period, although with important interannual variability (Figure ).…”

“…Seasonal snow and glacier melt in the semiarid Chilean Andes provide water to more than two thirds of Chile's population as well as maintaining key economic activities, ecosystems, and ecosystem services (Favier, Falvey, Rabatel, Praderio, & López, ). Central Chile is characterized by warm and dry summers, and humid cold winters, and ice melt provides a key contribution to runoff in dry periods and during late summer and autumn, in a water balance otherwise dominated by snowmelt (Ayala et al, ; Ohlanders, Rodriguez, & McPhee, ; Ragettli & Pellicciotti, ; Ragettli, Pellicciotti, Bordoy, & Immerzeel, ; Rodriguez, Ohlanders, Pellicciotti, Williams, & McPhee, ). While glaciers in the region have been receding and losing mass over the past few decades (Barcaza et al, ; Bown, Rivera, & Acuña, ; Malmros, Mernild, Wilson, Yde, & Fensholt, ; Mernild et al, ; Ragettli, Immerzeel, & Pellicciotti, ; Rivera, Acuña, Casassa, & Bown, ), the runoff response to climate and glacier changes is still poorly understood.…”

Understanding hydrological processes in glacierized catchments: Evidence and implications of highly variable isotopic and electrical conductivity data

“…This technique has been widely used to identify the contribution of event water, either identified as rainfall, snowmelt, or glacier melt. Whereas there are several studies quantifying the contribution of rain water to stream runoff since the late 1960s (Ladouche et al, ; Pinder & Jones, ; Sklash, Farvolden, & Fritz, ), few studies investigated the contribution of snowmelt (e.g., Beaulieu, Schreier, & Jost, ; Laudon, Hemond, Krouse, & Bishop, ; Penna, van Meerveld, Zuecco, Dalla Fontana, & Borga, ; Penna, Zuecco, et al, ) and glacier melt water (e.g., Cable, Ogle, & Williams, ; Engel et al, ; Maurya et al, ; Ohlanders, Rodriguez, & McPhee, ). The tracer‐based hydrograph separation relies on the end member mixing analysis (Christophersen & Hooper, ), a technique considering stream water as a mixture of water sources (end members) recognizable by their unique tracer signature.…”

The significance of mountain glaciers as sentinels of climate and environmental change

“…As climate conditions change, glacier mass responds accordingly, triggering modifications in the landscape and biogeochemistry of ecosystems at diverse spatial and temporal scales. However, those interpretations may well be shaped by imaginaries of spatial transformations (Watkins, 2015) implanted by changes observed elsewhere, without accounting for the particular nature of the landscapes analyzed, such as the importance of seasonal snow cover or high elevation wetlands on water availability (Buytaert et al, 2006;Ohlanders, Rodriguez, & McPhee, 2013). As mountain glaciers shrink, we may not only lose valuable archives of past climate and culturally relevant landscape features (Thompson, Mosley-Thompson, Davis, & Brecher, 2011) but we may also witness a transformation in the hydrological and biogeochemical cycles that geographers are uniquely poised to appreciate from a truly integrated perspective, using the many tools of observation and methods of tracing over many different scales.…”