MODULATION OF THE DIURNAL STREAMFLOW RESPONSE BY THE SEASONAL SNOWCOVER OF AN ALPINE BASIN

A 10 year record of streamflow from the 8 ha Martinelli Basin in the Colorado Front Range is dominated by snowmelt-produced flows. During the main part of the May-September flow season, the flows develop a marked 24-h cycle which often accounts for more than 50% of their variance, after removal of the seasonal trend. The amplitude and phase of this cycle vary in a similar fashion each year, showing a reduced amplitude and a forward phase shift as the summer progresses. These changes are explained by the reduction in the area of snow cover and its depth during the season. The phase shift may be used to estimate a catchment-scale hydraulic conductivity for a melting snow cover, yielding values in the range 40-80 cm h-1. These are consistent with other estimates based upon plot and laboratory studies.