Glaciers as a Proxy to Quantify the Spatial Distribution of Precipitation in the Hunza Basin

Accurate quantification of the spatial distribution of precipitation in mountain regions is crucial for assessments of water resources and for the understanding of high-altitude hydrology, yet it is one of the largest unknowns due to the lack of high-altitude observations. The Hunza basin in Pakista...

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Bibliographic Details
Published in:Mountain research and development 2012-02, Vol.32 (1), p.30-38
Main Authors: Immerzeel, Walter Willem, Pellicciotti, Francesca, Shrestha, Arun B
Format: Article
Language:English
Subjects:
Environment
Environmental aspects
Glacial ablation
Glacial accumulation
Glacial landforms
Glacial melting
Glacier mass balance
Glaciers
Hunza basin
Indus
Karakoram
Lapse rate
MountainResearch
Precipitation
Precipitation (Meteorology)
Remote sensing
Snow
Studies
Systems knowledge
Time series
Topographical elevation
vertical lapse rate
Watershed hydrology
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Summary:Accurate quantification of the spatial distribution of precipitation in mountain regions is crucial for assessments of water resources and for the understanding of high-altitude hydrology, yet it is one of the largest unknowns due to the lack of high-altitude observations. The Hunza basin in Pakistan contains very large glacier systems, which, given the melt, cannot persist unless precipitation (snow input) is much higher than what is observed at the meteorological stations, mostly located in mountain valleys. Several studies, therefore, suggest strong positive vertical precipitation lapse rates; in the present study, we quantify this lapse rate by using glaciers as a proxy. We assume a neutral mass balance for the glaciers for the period from 2001 to 2003, and we inversely model the precipitation lapse by balancing the total accumulation in the catchment area and the ablation over the glacier area for the 50 largest glacier systems in the Hunza basin in the Karakoram. Our results reveal a vertical precipitation lapse rate that equals 0.21 ± 0.12% m−1, with a maximum precipitation at an elevation of 5500 masl. We showed that the total annual basin precipitation (828 mm) is 260% higher than what is estimated based on interpolated observations (319 mm); this has major consequences for hydrological modeling and water resource assessments in general. Our results were validated by using previously published studies on individual glaciers as well as the water balance of the Hunza basin. The approach is more widely applicable in mountain ranges where precipitation measurements at high altitude are lacking.
ISSN:0276-4741
1994-7151
DOI:10.1659/MRD-JOURNAL-D-11-00097.1