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Discussion papers | Copyright
https://doi.org/10.5194/hess-2018-260
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 31 May 2018

Research article | 31 May 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).

Multi-scale temporal variability in meltwater contributions in a tropical glacierized watershed

Leila Saberi1, Rachel T. McLaughlin1, G.-H. Crystal Ng1,2, Jeff La Frenierre3, Andrew D. Wickert1,2, Michel Baraer4, Wei Zhi5, Li Li5, and Bryan G. Mark6 Leila Saberi et al.
  • 1Department of Earth Sciences, University of Minnesota - Twin Cities, Minneapolis, MN 55455, USA
  • 2Saint Anthony Falls Laboratory, University of Minnesota - Twin Cities, Minneapolis, MN 55455, USA
  • 3Department of Geography, Gustavus Adolphus College, St. Peter, MN 56082, USA
  • 4Construction Engineering, École de Technologie Supérieure, Université du Quebec, Montreal, Canada H3C 1K3
  • 5Department of Civil & Environmental Engineering, Pennsylvania State University, University Park, PA 16802-1294, USA
  • 6Department of Geography, The Ohio State University, Columbus, OH 43210-1361, USA

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 sub-humid watershed on Volcán Chimborazo, Ecuador, meltwater 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 melt contributions to discharge at timescales that complement melt generation, 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 meltwater contributions in tropical glacierized systems can change substantially at hourly to interannual timescales, due to climatic variability and surface to subsurface flow processes.

Leila Saberi et al.
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Leila Saberi et al.
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Short summary
The relationship among glacier melt, groundwater, and streamflow remains highly uncertain, especially in tropical glacierized watersheds in response to climate. We implemented a multi-method approach and found that melt contribution varies considerably and may drive streamflow variability at hourly to multi-year timescales, rather than buffer it, as commonly thought. Some of the melt contribution occurs through groundwater pathways, resulting in longer timescale interactions with streamflow.
The relationship among glacier melt, groundwater, and streamflow remains highly uncertain,...
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