8270 - Laserfiche WebLink

Home Browse Search

Stationary ice covers were observed in the Green River immediately following the appearance of frazil ice. The bridging location of the stationary ice cover was not reported, but the downstream limit of the stationary ice was consistently reported as the Ouray Bridge or further downstream. The upstream extent and periods of time the stationary ice cover was in place varied from year to year. In 1986-1987 the maximum upstream extent of the stationary ice was the Jensen Bridge (RM 302), observed on 28 January 1987 (Figure 30). The next day the ice cover retreated downstream. The ice cover was observed to stay in place from RM 270 downstream past Ouray Bridge (RM 250) for the next three weeks (Figure 31). The following year stationary ice was in place from early January through late February of 1988 and the upstream extent of the ice reached Chew Bridge (RM 316) (Figure 32). Short, disconnected areas of stationary ice were also seen upstream of the study area in Rainbow Park and Echo Park. The leading edge of the ice cover retreated to Jensen Bridge (RM 302) on 19 February, and to RM 294 by 27 February. In the winter of 1993-1994, the stationary ice reached Jensen Bridge (RM 302) on 2 February 1994 and extended upstream of the Jensen Bridge for an unreported distance. The stationary ice extent was not reported for the winter of 1994-1995, although it was reported that an "ice jam" occurred below Chew Bridge in the middle of December. The appearance of the ice cover was described as "smooth" downstream of Bonanza Bridge (RM 290) and having a "highly fractured and irregular surface" upstream of Bonanza Bridge (probably referring to ice formed as a result of static ice formation and juxtaposition of frazil pans, respectively). In February 1988 the ice cover thickness was measured to be 30-50 cm downstream of Bonanza Bridge with 30 cm of snow cover. In the winter of 1987-1988, frazil ice was observed to be deposited under the ice cover within an 11-mile reach, from RM 305 to RM 316. The layer of frazil ice deposited beneath the cover was measured as 60 to 90 cm thick in parts of the main channel. After the ice cover had retreated from this reach, accumulations of frazil ice were observed along the river banks that were 0.3 to 3 in thick beneath solid ice. At RM 310.3, 45 cm of solid ice was measured. 3.1.3.3 Winter of 1996-97 Field Survey Surveys of the ice cover conditions on the Green River were conducted during the winter of 1996-1997 as part of the field work for this study. The observations of the first survey, conducted on 18-19 December, indicated that a stationary ice cover was present from the Ouray Bridge to approximately RM 266 and that moving frazil pans were present upstream of that point (Table 3; Figure 33). Additional observations made on 28 December 1996 showed that the leading edge of the ice cover had progressed approximately 10 river miles further upstream (Figure 34; personal observation made by Bryan Cowdell, BIOMEST, Inc.). The next survey of ice conditions was conducted from 23-25 January 1997, just prior to initiation of fluctuating flows from Flaming Gorge Dam. During this period, a complete ice cover existed on the Green River from the Ouray Bridge (RM 248.2) to a location just -17-