To understand at a process level how changes in snowmelt rate will alter hydrologic partitioning of snowmelt between evaporative processes and streamflow, I use observations of evapotranspiration and snowmelt rate (ablation slope). We hypothesize that years with larger snowpacks that melt more rapidly are more efficient at driving infiltration below the root zone and contributing to later subsurface flow, which then becomes streamflow (Figure 1). There is a clear relationship between evaporative efficiency (ET/P) and snowmelt rate suggesting that years with more rapid snowmelt partition proportionally less water to evaporative processes than slow years (Figure 2). To explore the direct effects of snowmelt rate and the timing of snowmelt independently I use the Regional Hydo-Ecology Simulation System (RHESSys) in conjunction with a set of snowmelt scenarios that alter the timing and rate of snowmelt to examine the affect these two parameters have on hydrologic partitioning. It is clear that more water is partitioned to streamflow during the ablation season as snowmelt rate increases (Figure 3). The secondary pattern in the data cloud is that slow snowmelt can also generate proportionally high streamflow if it occurs early in the year when vegetation is unable to use the water (Figure 3). These relationships suggest that snowmelt rate exercises an important control on how water is portioned between hydrologic partitioning during the snowmelt season.