Estimating runoff from a glacierized catchment using natural tracers in the semi‐arid Andes cordillera

Abstract

This paper presents a methodology for hydrograph separation in mountain watersheds, which aims at identifying flow sources among ungauged headwater sub-catchments through a combination of observed streamflow and data on natural tracers including isotope and dissolved solids. Daily summer and bi-daily spring season water samples obtained at the outlet of the Juncal River Basin in the Andes of Central Chile were analysed for all major ions as well as stable water isotopes, O-18 and D. Additionally, various samples from rain, snow, surface streams and exfiltrating subsurface water (springs) were sampled throughout the catchment. A principal component analysis was performed in order to address cross-correlation in the tracer dataset, reduce the dimensionality of the problem and uncover patterns of variability. Potential sources were identified in a two-component U-space that explains 94% of the observed tracer variability at the catchment outlet. Hydrograph separation was performed through an Informative-Bayesian model. Our results indicate that the Juncal Norte Glacier headwater sub-catchment contributed at least 50% of summer flows at the Juncal River Basin outlet during the 2011-2012 water year (a hydrologically dry period in the Region), even though it accounts for only 27% of the basin area. Our study confirms the value of combining solute and isotope information for estimating source contributions in complex hydrologic systems, and provides insights regarding experimental design in high-elevation semi-arid catchments. The findings of this study can be useful for evaluating modelling studies of the hydrological consequences of the rapid decrease in glacier cover observed in this region, by providing insights into the origin of river water in basins with little hydrometeorological information. Copyright (c) 2016 John Wiley & Sons, Ltd

Assessing glacier melt contribution to streamflow at Universidad Glacier, central Andes of Chile

“…in the outer tropics in Peru, the groundwater contribution to outflow is greater than 24 % in all of the analysed valleys by Baraer et al (2014). In central Chile, Rodriguez et al (2016) estimated that the contribution associated with subsurface storage in winter and fall is 60 % in Juncal Norte Basin. However, it is difficult to estimate this contribution at Universidad Glacier without direct measurements.…”

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

“…Future research should aim at testing this hypothesis. Based on these results, future research in similar glacierized catchments should consider the following: The application of end member mixing analysis should account for the high spatial and temporal variability in the tracer signature of the water sources. Furthermore, some assumptions, such as the use of spring water as an end member (and proxy for groundwater) and the significant relation between elevation and isotopic composition of snow or glacier melt water, should be carefully checked. An isotope‐based two‐component hydrograph separation could be used to quantify the rain water fraction to stream runoff and to investigate the main hydrological mechanisms during rainfall–runoff events (Dahlke et al, ). Stream water EC dynamics could be analysed at the seasonal scale and during melt‐induced runoff events to assess temporal changes in glacier melt water contribution to stream runoff and to identify any hysteretic relations between streamflow and stream water EC (Engel et al, ; Zuecco, Penna, & Borga, ; Zuecco, Penna, Borga, & van Meerveld, ). Other tracers, such as major ions and trace elements, could be used to quantify the contribution of subglacial flow to stream runoff and perform a geographical source analysis (Rodriguez et al, ), or DNA injections could be applied to infer the main glacier flow pathways (Dahlke et al, ). …”

“…Despite the increasing number of studies focused on snow and snowmelt, we found few investigations in glacierized catchments. In these cases, the isotopic composition was usually determined for glacier melt water, snowmelt, and snow at few locations close to the glacier snout (e.g., Chiogna et al, 2014;Engel et al, 2016;Maurya et al, 2011;Pu et al, 2017;Rodriguez, Ohlanders, Pellicciotti, Williams, & McPhee, 2016;Vaughn & Fountain, 2005) or for ice cores at different elevations and few glacier melt water samples (e.g., Schmieder, Garvelmann, Marke, & Strasser, 2018;Stichler, Baker, Oerter, & Trimborn, 1982;Stichler & Schotterer, 2000;Zhou, Wang, & Joswiak, 2014). The difficulties and dangers in accessing glacial environments prevented more numerous studies and the collection of samples from several spatially distributed locations on the glacier surface.…”

Spatio‐temporal tracer variability in the glacier melt end‐member — How does it affect hydrograph separation results?

“…due to isotopic fractionation or chemical reaction of solutes with geology) except due to mixing of different waters (Baraer, McKenzie, Mark, Bury, & Knox, ; Mark, McKenzie, & Gómez, ). Environmental tracers, such as electrical conductivity (EC), and stable isotopes of water, such as oxygen‐18 (δ 18 O), have been used in tracer‐based hydrologic studies of glacierized catchments (e.g., Engel et al, ; Rodriguez, Ohlanders, Pellicciotti, Williams, & McPhee, ; Williams, Wilson, Tshering, Thapa, & Kayastha, ). The spatio‐temporal variability in end‐members violates the assumption of uniqueness and can be a limiting factor in applying mixing models.…”