Laserfiche WebLink
Natural streamflows of the Colorado River and Gunnison River are affected by many dams and <br />diversions upstream. The dams in the upper Colorado River basin are not large in comparison to <br />dams such as Glen Canyon or Flaming Gorge- the total volume of water stored in reservoirs in the <br />upper basin is equal to only about half of the average annual streamflow at the Colorado-Utah state <br />line. However, the reservoirs in the upper Colorado River basin are near the source of runoff, and <br />they alter the annual hydrograph significantly (we pursue this point later; see also Liebermann et <br />al., 1989). The Colorado River and Gunnison River carry moderately high sediment loads of 105 <br />to 10' metric tons per year (Elliot and DeFeyter, 1986). Most of this sediment is deri ved from the <br />soft shale and sandstone formations that underlie much of western Colorado and eastern Utah <br />(Iorns et al., 1965; Liebermann et al., 1989). This area is drained by a handfull of relatively small, <br />mostly unregulated tributaries which join the main-stem channels downstream from the upper basin <br />reservoirs. The Colorado River and Gunnison River thus both have two separate sources of <br />runoff and sediment: most of the runoff is derived from high elevation basins underlain by resistant <br />crystalline rocks, and most of the sediment is derived from low elevation basins underlain by <br />erodible sedimentary rocks. In typical years the water and sediment are delivered out of phase, <br />resulting in higher suspended sediment concentrations on the rising limb of the hydrograph than on <br />the falling limb. This has probably always been the case, but streamflows are now regulated, <br />whereas sediment inputs are not (we pursue the implications of this in more detail later). <br />Our detailed studies of channel change and sediment transport focus on a 90-km reach of the upper <br />Colorado River between Palisade, CO and Westwater, UT (Fig. 2). This reach has been important <br />historically to the Colorado squawfish, and it marks the upstream limit of their range in the main <br />stem of the Colorado River. The study area is further subdivided into three contiguous subreaches: <br />The 15-mile reach extends from the eastern end of the Grand Valley, near Palisade, CO, to the <br />confluence with the Gunnison River in Grand Junction; the 18-mile reach covers the next 29 km of <br />river from the confluence with the Gunnison River to the western end of the Grand Valley, near <br />Loma, CO; and the Ruby-Horsethief Canyon reach extends another 39 km downstream from <br />Loma, CO to Westwater, UT (Fig. 2). <br />109°00' 108°30' <br />39°15 <br />39°00' <br /> DeBeque • <br /> <br />? a <br />g Grand Junction Study Area <br />a <br />5i9 70 <br />i U 9095500 <br /> 200 <br />i <br /> <br />140 Loma <br />• <br />1 <br /> <br />8°a Ru'6yCanyc)nS 190 <br />Palisade <br />9163500 <br /> <br />0°` <br />Westwater 13 7B <br /> <br />R <br />Grand <br />180 185 <br />1 W StudySitas ?h Junction Peace <br />70 <br />' <br />, o USGS Gauging Stations 170 ecd? <br />1 <br />P <br />0 <br />000 <br />0? 1 2s km <br />1 1 F 'i??l 175 <br />0` <br />eo o 1 20 m °n?o' 9152500 <br /> 9 9 <br />109°00' <br />108°30' <br />Figure 2. Detailed map showing study reaches near Grand Junction, Colorado. <br />3el5 <br />39°00' <br />5