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STUDY AREA <br />These investigations took place in the lower 130 miles of the Green River (Figure 1). Our <br />sampling began where the river exits the Tavaputs Plateau and Book C1iffMountains (Gray <br />Canyon) and enters the Green River Valley. Further downstream the river has cut through the <br />Colorado Plateau and formed Labyrinth and Stillwater Canyons in present day Canyonlands <br />National Park. Through the Green River Valley river gradient is relatively steep, the channel <br />complex, and main channel habitats consist predominantly of runs and rifles over coarse <br />substrates with low velocity habitats developing during base flows. Tusher Diversion, located at <br />RM 128, spans most of the river diverting flows to an irrigation ditch and small hydropower <br />facility. Tusher Diversion does not likely act as a barrier to movements of adult native fish, but <br />may present a problem for the earlier life stages (further investigation has been warranted by the ,~ <br />Recovery Program). ~~~U1 <br />': tM'` <br />.r <br />As the river enters Labyrinth and Stillwater Canyons gradient decreases and substrates shift to <br />fine sediments, interspersed with alluvial hobble bars at the mouths of side canyons, eg. Millard <br />Canyon. : <br />Sampling was concentrated in three areas: near the town of Green River, Ut at RM 120, near the <br />confluence with the San Rafael (RM 97), and at Millard Canyon /Anderson Bottom (RM 33.5 / <br />31.0). <br />Flow in the Green River is characterized by great seasonal variability, typically on the order of <br />12:1, peak to baseflow. The two years of study were hydrologic extremes; 1994 a dry year and <br />1995 a wet year (Figure 2). The Green River, as measured by the USGS at the near Green <br />River, Ut gage, peaked at 11,700 cfs on May 22, 1994 and the following year at 29,300 cfs on <br />June 18. <br />DRAFT <br />