Description:
The infuence of glaciers on seasonal distribution of river fow is strongly dependent on annual temperature and precipitation cycles, and the proportion of the catchment occupied by glacier ice. Figure 4 compares precipitation and river fow data for heavily and lightly glacierized catchments in the European Alps and Peru. In the European Alps, runoff is greater than precipitation in summer in both heavily and lightly glacierized catchments. This is because the Alps experience a large seasonal temperature cycle, and recipitation falls as snow in winter, providing a source of meltwater into the summer even where no glaciers are present. In Peru, on the other hand, temperature varies less throughout the year and there is less annual variation in snow cover. Thus, runoff is much greater than precipitation in the dry season (June–August) in heavily glacierized catchments, but not in lightly glacierized catchments. The implication is that the removal of glaciers from catchments will have a much larger impact on water resources in Peru than in the European Alps. Without a glacial source of meltwater, river discharges closely follow the precipitation cycle, with very little runoff in the dry season.