Multi-scale temporal variability in meltwater contributions in a tropical glacierized watershed
<p>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 a...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-01-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/23/405/2019/hess-23-405-2019.pdf |
| Summary: | <p>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.</p> |
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| ISSN: | 1027-5606 1607-7938 |