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<br />
<br />Field Work
<br />
<br />An attempt was made to select reference backwaters at the Island Park,
<br />Jensen, Ouray, and Sand Wash sites that would exist at most or every
<br />flow chosen for study. The logistical nature of work on the river did
<br />not allow each site to be visited on the same day photography was
<br />acquired for that site. Consequently, the river flows during field
<br />visits did not correspond well with the flows present during
<br />photographing. However, most sites were visited during the same week
<br />that the photography was acquired, the flow for that day was noted, and
<br />field measurements were taken.
<br />
<br />Table 12 (Appendix A) presents the flow, identifier, river mile, depth
<br />(inches) at three locations at the mouth, mid, and end points of each
<br />backwater, and the length (feet), for each date a site was visited. No
<br />reference backwaters selected at the highest flow (approximately 5,260
<br />cfs) were still present at any lower flow.
<br />
<br />Island Park - Three reference backwaters were selected for study at
<br />Island Park. Reference backwaters A (river mile 329.8) and C (river
<br />mile 330.5) were present for six flows, from July 11, 1987 (2,365 cfs)
<br />until August 12, 1987 (1,031 cfs). Reference backwater B (river mile
<br />329.9) was present for five flows, from July 16, 1987 to August 12,
<br />1987. At 2,365 cfs, reference backwater A was 111 feet long, and the
<br />average depth was 7 inches. It reached it's maximum length and depth at
<br />1,895 cfs (186 feet and 11.3 inches, respectively). At the lowest flow
<br />measured, backwater A was only 51 feet in length with an average depth
<br />of 6 inches. Reference backwater C was initially 270 feet (maximum
<br />length) in length with an average depth of 9 inches at 2,365 cfs.
<br />Backwater C gradually declined in length and average depth, and at 1,031
<br />cfs was 40 feet in length with an average depth of 7 inches. Reference
<br />backwater B decreased from 169 feet in length at 1,895 cfs to 105 feet
<br />at 1,230 cfs, and then increased to 162 feet at 1,031 cfs. The average
<br />depth of backwater B ranged from 11 inches at 1,031 cfs to 7 inches at
<br />1,895 cfs.
<br />
<br />Jensen - Three reference backwaters were studied at the Jensen site.
<br />Reference backwater A (river mile 307.5) was present for six flows, from
<br />2,392 cfs to 1,028 cfs. Reference backwaters B (river mile 307) and C
<br />(river mile 309) were present for five flows from 1,978 cfs to 1,028
<br />cfs. Backwater A was initially 178 feet in length with an average depth
<br />of 22 inches and reached a maximum length of 540 feet (average depth 22
<br />inches) at 1,142 cfs and a maximum average depth of 23 inches (length
<br />531 feet) at 1,028 cfs. Backwater B was initially 161 feet in length
<br />with an average depth of 9 inches and increased to it's maximum length
<br />(509 feet) and average depth (17 inches) at 1,028 cfs. Backwater C
<br />ranged in length from 282 feet at 1,028 cfs to 224 feet at 1,687 cfs.
<br />Average depth of this backwater ranged from 15 inches at 1,383 cfs to 21
<br />inches at 1,978 cfs.
<br />
<br />Ouray - Two backwaters were studied at the Ouray site. Reference
<br />backwater A (river mile 251) was present for four flows, from 1,683 cfs
<br />to 1,031 cfs, and reference backwater B (river mile 261.5) was present
<br />for six flows, from 2,635 cfs to 1,031 cfs. Backwater A was a relatively
<br />long backwater, ranging from 423 feet at 1,374 cfs to 297 feet at 1,031
<br />
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