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downstream of Razorback Island (RM 310.8) (Figure 35), with the following exceptions: continuous open leads, one-quarter to one-third of the river width, were observed within the Ouray National Wildlife Refuge (RM 251.3-254), along Hamacker Bottom (RM 270-276.4), near Collier Draw (RM 286.5-287.2), and near Bonanza Bridge (RM 288.8-289.8). In the remaining reaches, isolated, discontinuous leads were fairly common, but they accounted for only a small portion of the total ice-covered area. Between RM 310.8 and 314.5 the river made a gradual transition from a complete ice cover to open water (Figure 35). An ice jam 90-m long was observed on 24 January 1997 in the bend below Chew Bridge at RM 316.3. No ice was observed from the Chew Bridge to the confluence of the Yampa River and it is likely that the main channel of the Green River was open to Flaming Gorge Dam. No floating frazil was observed from Split Mountain Campground to Chew Bridge during 23-30 January. Air temperatures in the study reach moderated during 25-28 January 1997 and the snow and ice around the edges of open leads was wet. Shoreline cracks were also wet in places, indicating that melting of the ice cover was occurring. An aerial inspection on the afternoon of 28 January, approximately 3 days after the propagation waves associated with peaking operations at Flaming Gorge Dam had started passing through the study reach, revealed that the small ice jam below Chew Bridge had broken up and that the leading edge of the ice cover had moved from RM 310.8 to RM 309.8. Surveys of ice cover distribution from 29-30 January found that the stationary ice cover had retreated to RM 306 (Figure 36). Otherwise, ice conditions appeared similar to the conditions that existed on 25 January (Figure 35). Based on these observations, the movement of the location of the leading edge of the ice cover occurred in two stages: the first movement was from RM 310.8 to RM 309.8 by 1500 hours on 28 January 1997, and the second was movement of the leading edge from RM 309.8 to RM 306 early on 29 January. The ice motion detector at RM 308.2 indicated that the ice cover at that location broke up at 0600 hours on 29 January. A team arrived at this location five hours later to find an open channel with small ice pieces and floes floating past. The post-breakup water level was approximately 1.2 m lower (based upon examination of the location of the shear walls of ice remaining along the shoreline [White and Zufelt, 1994]) than the pre-breakup ice surface elevation, attributable to the increased conveyance of the river after removal of complete ice cover. One mile downstream, between RM 307.2 and RM 306.0, the river made a gradual transition from completely open to entirely ice covered. There was little ice debris at the leading edge location at RM 306.0, so ice pieces had either melted in transit or had been carried beneath the upstream edge of the ice cover. Within this transition reach, at 1140 hours on 29 January, a 100-ft-long ice jam spanned the open portion of the channel at RM 307.0. Floes colliding with the upstream edge of the jam, passed beneath the accumulation, and emerged at the downstream end. Downstream of the new leading edge location (RM 306.0) the condition of the ice cover appeared unchanged from conditions that existed during the steady flow observations made on 23-25 January. During a subsequent aerial inspection of the study reach on 20 February 1997, it was -18-