Spatially heterogeneous discharge of glacial meltwater to drainages surrounding the ablating Coropuna ice cap, Peruvian Andes

As tropical glaciers recede in response to global warming, glaciated watershed resilience is threatened by the loss of these important water reservoirs. In the Cordillera Occidental, Peru, we investigate the importance of glacial meltwater to mountain groundwater recharge and subsequent discharge to streams surrounding the rapidly retreating Coropuna ice cap. Using stable isotopes, solute concentrations, and radiocarbon activity, our results suggest that in remote ungauged systems, glacial input can be determined via geochemical analysis and a simple mixing model approach. We find that the proportion of glacial meltwater contribution to groundwater and surface waters is spatially heterogeneous. Differences between drainages are attributed to the degree of melting of headwater glaciers and the routing of waters through volcanic strata. These results provide evidence that glacial meltwater recharge is highly variable even within the same mountain block. Furthermore, the effects on streamflow will be disproportionate as the watersheds approach an ice-free state.