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Hydrogeology of an alpine talus aquifer: Cordillera Blanca, Peru

May 21, 2019

The dramatic loss of glacial mass in low latitudes is causing shifts in downstream water availability and use during the driest months of the year. The world’s largest concentration of tropical glaciers lies in the Cordillera Blanca range of Peru, where glacial runoff is declining and regional stresses are emerging over water resources. Throughout the Cordillera Blanca, groundwater inputs from alpine meadow–talus complexes, locally known as pampas, supply proglacial streams with up to 80% of their flow during the region’s dry season. Structural knowledge of the pampa aquifers is needed to estimate their drainable groundwater storage capacity and residence time, to elucidate the role and importance of alpine groundwater storage in the regional water budget of the Cordillera Blanca. To understand the structure of these proglacial aquifers, multiple near-surface geophysical methods were implemented in a proglacial valley near dense networks of spring-fed tributaries. Geophysical results and borehole logs suggest groundwater is stored in a confined aquifer composed of buried talus deposits overlain by lacustrine clay, while deeper portions of the unit, 10–15 m in depth, are relatively clay-free and more hydraulically conductive. Based on these findings and assumptions of aquifer porosity, the pampas of the Callejon de Huaylas may store from 0.006 to 0.02 km3 of groundwater. Furthermore, these findings suggest that the talus aquifers of the Cordillera Blanca were formed in proglacial lakes, followed by infilling with fine lacustrine sediments that confine lower units and allow for groundwater discharge to springs via macropores and preferential flow.

Publication Year 2019
Title Hydrogeology of an alpine talus aquifer: Cordillera Blanca, Peru
DOI 10.1007/s10040-019-01982-5
Authors Robin Glas, Laura K. Lautz, Jeffrey M. McKenzie, Robert Moucha, Daniel Chavez, Bryan Mark, John W. Lane
Publication Type Article
Publication Subtype Journal Article
Series Title Hydrogeology Journal
Index ID 70215399
Record Source USGS Publications Warehouse
USGS Organization Dakota Water Science Center; WMA - Earth System Processes Division