Runoff Processes during Snowmelt

During the snowmelt period of 1967, snowmelt runoff from three pastured plots was measured as it moved to the stream channel over the ground surface, through the topsoil, and through the phreatic zone. Because of the presence of a thin layer of concrete frost in the normally porous topsoil, the infiltration capacity of the soil was reduced to a very low value. Almost one half of the meltwater left the plots as overland flow. Discharge rates, total volumes, and timing of this portion of the runoff were strongly controlled by incoming shortwave radiation. The response of subsurface flow to melting was heavily damped by storage and transmission of water in the soil. Combined daily hydrographs of runoff were dominated by overland flow. Comparison of the timing of such hydrographs with concurrent stream channel hydrographs from basins of the Sleepers River Experimental Watershed suggests that overland flow was a major control of the diurnal fluctuations of streamflow. Previous studies in the same area have demonstrated that much of the overland flow contributing to the responsive stream hydrographs of these basins originates on saturated areas of the watershed.