Glacier retreat changes diurnal variation intensity and frequency of hydrologic variables in Alpine and Andean streams

The impacts of glacier mass and area loss are assumed to affect stream hydrology and related ecosystems. We applied wavelet analysis to high frequency time series of discharge, conductivity, turbidity, air and water temperature in mountain streams influenced by a gradient of diverse glacier catchment coverages from 0 to 28%. All parameters were recorded during 200–250 day period in 24 mountain streams in Switzerland and Ecuador. We interpreted the range of glacier coverage as a proxy of glacier melt effect linked to modification in glacier cover based on a space-for-time substitution approach. We used the diurnal variation power and frequency as hydrological parameters to quantify the intensity and occurrence of significant diurnal variations in the different mountain catchments. Our results show that the reduction in glacier cover would reduce the intensity and occurrence of diurnal variations in discharge, turbidity and conductivity, and the intensity of diurnal variations in water temperature. Discharge and conductivity were affected in a similar way, while the impact on turbidity was less significant. Furthermore, due to their different climatic regimes, the diurnal discharge in the tropical Andes was more impacted than in the Alps, indicating that the impacts of global change on glacier streams would be stronger in the tropical Andes than in the Alps.