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Thus, the hydrograph has been modified the most for the largest water years, which typically are the years that cause the most channel change and during which woody riparian plant species (such as cottonwoods) reproduce. Third, the differences are particularly large between the June regressions; June 1946-1962 has the highest regression line, while June 1963-1993 the lowest. As shown in Figure 1, average to large water years have total annual flows of 3 to 4 million acre feet. Using the regressions shown in Figure 6 it can be determined that the maximum June flows pre- and post-Flaming Gorge are different by 7,000 to 9,000 cfs. For example, a runoff year producing 3 million acre feet would have had a peak discharge of approximately 20,000 cfs pre-Flaming Gorge, but a peak neaxer 13,000 cfs post-Flaming Gorge. A runoff year producing 4 million acre feet would have had a peak discharge of approximately 26,000 cfs pre-Flaming Gorge, while today a peak of 17,000 is predicted. These difference are. significant when considering the potential for using controlled releases from Flaming Gorge Reservoir to create the types of flows required to create flooding conditions in the Escalante region, and to provide the types of environments conducive to native fishes and plant species. Mean daily flows for the spring runoff period of 1993 are shown in Figure 7 (data courtesy G. R. Smith, U.S.F.W.S.). The Yampa River had a sharp increase in flow volume in mid-May followed by a short period of sustained high flow; approximately 2 weeks. A cold period in early June reduced the melt rate of mountain snow and flows decreased from early to mid-June. Flows peaked again in late June. Figure 7 illustrates the fact that flow periodicity at Jensen is derived from Yampa River flows. The approximately 4,300 cfs discharged from Flaming Gorge increased the duration of high water, but the peak discharges are still significantly below what might have been expected on the Green River prior to dam closing. The 1993 water year was the largest since 1986, yet the period of high water was quite short, and the peak flow was not particularly high (see Figure 2). Only one day had flows exceeding 20,000 cfs, but prior to 1953 a water year such as this may have produced flows greater than 20,000 cfs for up to 2 to 4 weeks duration. Overbank flows (>15,000 cfs) occurred for approximately.3 weeks this year, but prior to the Dam may have occurred for 4 to 7 weeks. This extensive period of inundation would have been long enough for larval fishes to move into floodplain wetlands and grow for more than 1 month and still have sufficient flaws to return to the river. 13