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

The mean river-wide depth to embeddedness (DTE) value was greater in riffles than in runs.
Significant differences between habitats were found for each sample date (Figure 19). On
each date, the DTE values were about 5 cm greater in riffles than in runs. A similar pattern
was found in the Gunnison River with riffle DTEs averaging 4-5 cm greater than run DTEs.
The same temporal pattern was found for both riffles and runs with a slight increase
(although not significant) between the spring and fall of 1994 followed by a significant drop
in DTE values in the spring of 1995. After spring runoff, the fall 1995 DTE levels showed
significant increases and were comparable to the 1994 samples in both habitat types. The
comparison between the Colorado River and the single stratum of the Gunnison River
showed that only the run habitats in spring of 1994 and fall of 1994 were significantly
different between rivers. The Colorado River runs had deeper DTE values than the Gunnison
River.
COLORADO RIVER-RIFFLES COLORADO RIVER-RUNS
Mean Depth to Embeddedness Mean Depth to Embeddedness
1e 10

14 ...... ?_____ _{ ._ .................. 14 .......... !
12
? 12 .... ..... ...
91 10
0 ?...... _
_ u

c 77
--
S 8 ..
._ _. - .. ,?
...
4 ............_.. ........... ._....... __.., ___-_ 4
2 2 .........
0 _....._.......
0
Spring 1994 Fall 1994 Spring 1995 Fall 1995 Spring 1994 Fall 1994 Spring 1995 Fall 1995
PERIOD PERIOD
GUNNISON RIVER-RIFFLES GUNNISON RIVER-RUNS
Mean Depth to Embeddedness Mean Depth to Embeddedness
1 16

14 14 ......... _._._ .,-_ __. _._._............
'

12
..._......... .. ..._..:........ .... .... .
_............
...
_._ .............

12 ..... _..
... .........
.__._ ..
`_. ___ __... _....... _.
'910 .. 610 .... .. ....
0 8 _ _. 0 8 ....
..

4 4-
2 .... 2 ..
_.

0 ___. __ - ___
0 .....
....
Spring 1994 Fall 1994 Spring 1995 Fall 1995 Spring 1994 Fall 1994 Spring 1995 Fall 1995
PERIOD PERIOD
Figure 19. The seasonal distribution of depth to embeddedness for riffles and runs in the Colorado River (above) and the
Gunnison River (below).
The mean percent surface area embedded for riffles and runs (Figure 20) indicated that riffles
were always less than 20 percent embedded while runs were always greater than 35 percent
embedded. These differences were significant for all sample dates. The seasonal patterns
within each habitat types were similar except for during fall 1994. During that period, riffle
PAE values decreased relative to the spring 1994 levels while run values increased. This
change from the spring levels was significant for both habitats. By spring 1995, riffle PAE
levels had increased again while the run PAE levels did not significantly change.
19