|
<br />14
<br />
<br />The average size of all backwaters at the 9uray site was much larg1r than at
<br />Island Park and Jensen, ranging from 417 m at 1,381 ft3/s to 831 m at
<br />1,773 ft3/s. Backwaters per mile ranged from 3.9 it 5,260 ft3/s to 6.6 at
<br />1,381 ft3/s, somewhat less than Island Park and Jensen. Backwater area Prr
<br />mile at Ouray was the most of any site, ranging from 1,678 m2 at 5,260 ft /s
<br />to 4,697 m2 at 1,687 ft3/s.
<br />
<br />Sand Wash
<br />
<br />The area for interpreted classes for each flow at Sand Wash are presented in
<br />table 10. The lowest backwater area at the Sand Wash site occurred at
<br />5,260 ft3/s (4,962 m2) (table 11). Backwater area increased 71 percent to
<br />8,466 m2 at 2,423 ft3/s, and increased again (32 percent) at 1,773 ft3/s
<br />where it was maximized at 11,147 m2. Backwater area decreased somewhat at
<br />1,687 ft3/s, decreased substantially at \,430 ft3/s to 5,713 m2, and then
<br />increased again (92 percent) at 1,381 ft Is. The low backwater area at
<br />1,430 ft3/s was an anomaly and examination of flow data indicated that
<br />riverflow was actually lower at this time than at any other flow. The
<br />1,430 ft3/s flow was maintained for one day at the Jensen gauge and had not
<br />reached the Sand Wash site when the photogra~hY was acquired. The actual
<br />flow was probably less than that at 1,101 ft Is. Backwater formation at
<br />1,430 ft3/s was further complicated by the chronology of flows as previously
<br />discussed.
<br />
<br />The flow at Sand Wash was difficult to determine because the White and
<br />Duchesne Rivers enter the Green River between Sand Wash and the Jensen
<br />gauge. Furthermore, the Price River enters the Green River between the Sand
<br />Wash site and the Green River gauge which would cause the Green River gauge
<br />readings to be higher than the flow at Sand Wash. Despite these facts, it
<br />was still apparent that backwater area at the Sand Wash site was maximized
<br />at flows below 2,423 ft3/s as measured at the Jensen gauge.
<br />
<br />The total number of backwaters ranged from 11, at 1,430 and 1,101 ft3/s, to
<br />22 at 5,260 ft3/s (table 10). Sand Wash site was unique because backwater
<br />number was maximized at the highest flow. Furthermore, backwater numbers
<br />were much more evenly distributed among the various size classes than at the
<br />upper sites. Backwaters per mile ranged from 2.9 at 1,430 and 1,101 ft3/s
<br />to 5.8 at 5,260 ft3/s, the lowest of the upper four sites. Backwater area
<br />per mile ranged from 1,306 m2 at 5,260 ft3/s to 2,933 m2 at 1,773 ft3/s.
<br />Average backwater size ranged from 226 m2 at 5,260 ft3/s to 906 m2 at
<br />1,381 ft3/s. Generally, the Sand Wash site had substantially fewer
<br />backwaters and less backwater area per mile than the three upper sites.
<br />There were usually more bank than channel backwaters, and backwaters were
<br />relatively evenly distributed among size classes.
<br />
<br />Mineral Bottom
<br />
<br />The area for interpreted classes at each flow for Mineral Bottom are
<br />presented in table 12. Backwater area at Mineral Bottom was maximized at
<br />3,261 ft3/s at the USGS Green River gauge (Jensen gauge was 2,423 ft3/s)
<br />with 3,224 m2 (table 13). Backwater numbers were also maximized at
<br />
|