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

These relationships follow Lambert-Beers law with the expression:
Where IG is surface light intensity, I. is intensity at
Ix = e-kr depth x, k is the extinction coefficient and x is
water depth.
Utilizing water quality data
(turbidity) collected at the same time
as light profiles, a comparison was
made between the calculated
extinction coefficient k and water
turbidity. This relationship, with an r2
= 0.75, is presented in Figure 9. It is
clearly apparent that the rate of light
extinction in the Colorado and
Gunnison rivers is related to the
suspended particles within the water
column.
COLORADO AND GUNNISON RIVERS
LIGHT PROFILES
100
W
so
U) s0
LL
O 40
X 20
J
0
0 5 10 15 20 25 30
WATER DEPTH (cm)
?- COLORADO SP 940- COLORADO SP 9SX7 GUNNISON SP 9Lg GUNNISON SP 9
Figure 8. The average light profiles for the Colorado and Gunnison
rivers during the spring of 1994 and 1995
At the conclusion of each sampling
period, a river-wide synoptic water
quality survey was conducted. Water
quality samples were collected from
each river reach and the entire 11
strata were sampled within two days.
Grab samples of micro-nutrients
nitrogen and phosphorus, as well as
turbidity, were preserved in the field
and later analyzed in the laboratory.
The river-wide mean concentrations
of these water quality parameters are
presented in Figure 10.
Figure 9. The linear relationship between the calculated extinction
coefficient (k) and water turbidity in the spring of 1995 in the
Colorado River
The concentrations of total phosphorus and total inorganic nitrogen (NH3+NO2+NO3)
demonstrated the same temporal trends, with the highest average concentration occurring in
fall 1994 and the lowest in fall 1995. Although there were no significant differences in total
phosphorus concentrations by time period, there were significant differences in
concentrations over time for total inorganic nitrogen. The data indicate that all periods were
significantly different except the spring of 1994 and 1995 which were similar.
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