8250

• UCREFRP Catalog Number: 8250
• Author: Lamarra, V. A.
• Title: Longitudinal Variation in the Trophic Structure of the Upper Colorado River.
• USFW Year: 1999.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

COLORADO RIVER COLORADO RIVER
Mean Particle Diameter. D16 Mean Particle Diameter. D50
2ao
20
150 .......... ._ ___.......... 150 .......... ... . . ........ .........
_.. - ..... ... .. .....
s 100 -- .... ............. ..... ...... °100 ... _ - -
....
..... ..__.
....
. ....
50
?
..... _ ..
0
Spina 1991 FaN 798/
SWN 1995 F.11 1985 0 Spina 1851 FaN 1881 Spiny 1985 PoN 1885
PEPoOD PERIOD
Figure 4. The mean and 95% confidence interval of the D16 and D50 values calculated for the river-wide substrate samples
collected in 1994 and 1995 in the Colorado (above) and Gunnison (below) rivers.
COLORADO RIVER GUNNISON RIVER
Mean Depth to Embeddedness Mean Depth to Embeddedness
10 10

e ........... ....

.....
...
....

....

e
e
e

...................
la _._ ...... ---- --- -
............
...........

".___ ......
1 -
2 -- ......
_'..............

..... .........-

2
D _ ._........ .• ........
.
Spina 1991
Fall 1591 Sp.9 1885
FaN 1885
D
Spiny 1994 F.0 1991 Spxp 1885
FNI 1895 '
PERIOD PERIOD
Figure 5. The mean and 95% confidence interval of the depth to embeddedness values calculated for the river-wide
substrate samples collected in 1994 and 1995 in the Colorado (left) and Gunnison (right) rivers.
The PAE data followed the same pattern as the DTE data (Figure 6). The mean percent of
surface area embedded in spring 1994 was 25 percent and increased to 30 percent by fall
1994. This change was not significant. However, the increase to 36 percent in spring 1995
was significantly different from the 1994 results. The decrease in mean PAE to 28 percent
in fall 1995 was significantly different than results from the previous spring (1995), but was
not significantly different from the 1994 mean PAEs. A comparison between the Gunnison
River percent embedded data to the Colorado River indicates that embeddedness in spring
1994 was significantly greater in the Gunnison (51%) than in the Colorado River (25%). In
the fall of 1994 and 1995, embeddedness in the Gunnison River remained constant (25%)
and was not significantly different from the Colorado River.
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