Spatial and temporal variation in physical habitat conditions of low-gradient reaches of Rocky Mountain streams during fall and winter

Physical habitat features of low-gradient (channel slope < 2 %) stream reac hes during fall and winter varied with elevation and drainage area as well as between years in the Medicine Bow Mountains, southern Wyoming. The exten t of snow cover increased and surface ice decreased during winter with incr easing elevation and declining drainage area. At high-elevation (> 3,200 m above mean sea level), the streams were small and entirely bridged by snow and had no surface ice, and flows were a small proportion of the average an nual flow (Q(AA)) Moderate-sized, middle-elevation (2,444 - 3,149 m) stream s were not bridged by snow and had patches of surface ice and snow as well as open water on pools and riffles, and flows were an intermediate proporti on of Q(AA). Larger streams at the foot of the mountains (2,242 - 2,374 m) had no snow cover, pools were entirely covered by surface ice, and flows we re a relatively high proportion of Q(AA). Variation in discharge and physic al habitat features occurred between the two years, especially at middle an d low elevations.