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

Leila Saberi, Rachel T. McLaughlin, G. H. Crystal Ng, Jeff La Frenierre, Andrew D. Wickert, Michel Baraer, Wei Zhi, Li Li, Bryan G. Mark

Research output: Contribution to journalArticle

1 Citation (Scopus)

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.

Original languageEnglish (US)
Pages (from-to)405-425
Number of pages21
JournalHydrology and Earth System Sciences
Volume23
Issue number1
DOIs
StatePublished - Jan 24 2019

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meltwater
glacier
watershed
melt
timescale
streamflow
groundwater
time series analysis
subsurface flow
tropical region
hydrograph
climate modeling
infiltration
warming
water resource
runoff
rainfall

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Multi-scale temporal variability in meltwater contributions in a tropical glacierized watershed. / Saberi, Leila; McLaughlin, Rachel T.; Crystal Ng, G. H.; La Frenierre, Jeff; Wickert, Andrew D.; Baraer, Michel; Zhi, Wei; Li, Li; Mark, Bryan G.

In: Hydrology and Earth System Sciences, Vol. 23, No. 1, 24.01.2019, p. 405-425.

Research output: Contribution to journalArticle

Saberi, Leila ; McLaughlin, Rachel T. ; Crystal Ng, G. H. ; La Frenierre, Jeff ; Wickert, Andrew D. ; Baraer, Michel ; Zhi, Wei ; Li, Li ; Mark, Bryan G. / Multi-scale temporal variability in meltwater contributions in a tropical glacierized watershed. In: Hydrology and Earth System Sciences. 2019 ; Vol. 23, No. 1. pp. 405-425.
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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 Volc{\'a}n 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 Ni{\~n}o 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.",
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AU - McLaughlin, Rachel T.

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AU - Wickert, Andrew D.

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AU - Zhi, Wei

AU - Li, Li

AU - Mark, Bryan G.

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AB - 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.

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