Quantifying groundwater–surface water interactions in a proglacial valley, Cordillera Blanca, Peru

Abstract

A myriad of downstream communities and industries rely on streams fed by both groundwater discharge and glacier meltwater draining the Cordillera Blanca, Northern Peruvian Andes, which contains the highest density of glaciers in the tropics. During the dry season, approximately half the discharge in the region's proglacial streams comes from groundwater. However, because of the remote and difficult access to the region, there are few field methods that are effective at the reach scale to identify the spatial distribution of groundwater discharge. An energy balance model, Rhodamine WT dye tracing, and high‐definition kite‐borne imagery were used to determine gross and net groundwater inputs to a 4‐km reach of the Quilcay River in Huascaran National Park, Peru. The HFLUX computer programme (http://hydrology.syr.edu/hflux.html) was used to simulate the Quilcay River's energy balance using stream temperature observations, meteorological measurements, and kite‐borne areal photography. Inference from the model indicates 29% of stream discharge at the reach outlet was contributed by groundwater discharge over the study section. Rhodamine WT dye tracing results, coupled with the energy balance, show that approximately 49% of stream water is exchanged (no net gain) with the subsurface as gross gains and losses. The results suggest that gross gains from groundwater are largest in a moraine subreach but because of large gross losses, net gains are larger in the meadow subreaches. These insights into pathways of groundwater–surface water interaction can be applied to improve hydrological modelling in proglacial catchments throughout South America. Copyright © 2016 John Wiley & Sons, Ltd.

Influence of a rock glacier spring on the stream energy budget and cold‐water refuge in an alpine stream

“…Helen Creek is thus subject to a net cooling effect in the downstream direction over the 1.4 km length of stream over which temperatures were measured (from “upper creek” to “lower creek”). Conversely, solar radiation is the largest component of the distributed stream energy fluxes at the studied reach of Helen Creek, as has been observed in other alpine streams (Khamis, Brown, Milner, & Hannah, ; Magnusson et al, ; Somers et al, ). It is remarkable that the creek exhibits net longitudinal cooling over such a distance despite a positive distributed stream energy budget largely driven by solar radiation.…”

Rapid decline of snow and ice in the tropical Andes – Impacts, uncertainties and challenges ahead

“…In all four valleys they surveyed, the groundwater contribution to runoff was above 24% during the dry season, suggesting that groundwater provides a substantial contribution to river discharge from these glacierized catchments. Another study in a proglacial catchment of the Cordillera Blanca by Somers et al (2016) confirms these results. Their study indicates that river discharge during the dry season experiences a net gain of almost 30% from the underlying aquifer.…”

“…Their study indicates that river discharge during the dry season experiences a net gain of almost 30% from the underlying aquifer. Both Gordon et al (2015) and Somers et al (2016) stress, however, that groundwater itself is at least partially recharged through glacier meltwater. Hence it remains an unresolved question to what extent the hydrology of the underlying aquifer itself will be affected by continued glacier retreat and eventual complete disappearance.…”

Does hillslope trenching enhance groundwater recharge and baseflow in the Peruvian Andes?

“…In Peru, glaciological and hydrological research in the Cordillera Blanca has explored the rapid recession of glaciers (Georges, ; Mark & Seltzer, ; Schauwecker et al, ) and their threat to water resources (Baraer et al, ; Mark, Bury, McKenzie, French, & Baraer, ), as well as the mediating influence and importance of groundwater discharge to alpine streams (Baraer et al, ; Gordon et al, ; Somers et al, ).…”