8132

• UCREFRP Catalog Number: 8132
• Author: Lieberman, D. and T. Burke.
• Title: Limnology and Drift of Particulate Organic Matter Through the Lower Colorado River.
• USFW Year: 1991.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

the observed means for POM (table 10). The >505-
µm POM was least abundant at Parker Dam for all
sampling dates. Sampling of the >505-µm POM was
Table 9.-F-test results based on ANOVA
between all stations and >25-µm dry
weight (DW), and >25-µm POM for
phase 1 (Oct. 1986 through June 1987).
Mean Station
g/m3 Tukey
grouping
>25-µm Dry weight, DW
32.80 Imperial Dam A*
29.55 Yuma A
12.94 Cibola C B
3.95 Palo Verde Diversion Dam C
1.53 Park Moabi C
0.84 Headgate Rock Dam C
.10 Davis Dam C
.10 Parker Dam C
>25-µm POM
0.73 Yuma A
.72 Imperial Dam A
.46 Cibola B
.10 Palo Verde Diversion Dam C
.09 Park Moabi C
.08 Headgate Rock Dam C
.06 Davis Dam C
.05 Parker Dam C
* Means with the same grouping are not signif-
icantly different at the 0.05 confidence level.
Table 10.-F-test results based on ANOVA
between all stations and >505-µm dry
weight (DW), and >505-µm POM for
phase 1 (Oct. 1986 through June 1987).
Mean Station Tukey
g/m3 grouping
>505-µm Dry weight, DW
0.45 Cibola A*
.08 Imperial Dam B
.07 Headgate Rock Dam B
.03 Davis Dam B
.03 Palo Verde Diversion Dam B
.03 Park Moabi B
.03 Parker Dam B
.10 Yuma B
>505-µm POM
0.04 Imperial Dam A
.03 Headgate Rock Dam A
.03 Cibola A
.03 Davis Dam A
.03 Yuma A
.02 Park Moabi A
.01 Parker Dam A
.02 Palo Verde Diversion Dam A
* Means with the same grouping are not signif
icantly different at the 0.05 confidence level.
discontinued after phase 1 because its contribution
to total POM was minimal.
Finally, figure 4 shows that the two tailwater stations
(Davis and Parker Dams) had greater amounts of total
POM than stations downstream from them (Park
Moabi and Headgate Rock Dam). The figure also
shows that the >25-µm POM did not follow this
trend. In both cases, there was less POM in the >25-
µm size-fraction at the tailwater stations than at the
following respective downstream stations. Both
reservoirs were releasing more POM in the <25-
µm size-fraction which accounted for the majority
of the total POM in the tailwaters.
The material captured by sieving through the various
nets was both inorganic and organic material. As
shown in table 11, inorganic material often com-
prised the greatest proportion of the particulate
matter. Davis Dam was the only sampling station
to show greater than 50 percent of the total
particulate matter to be POM (organic matter). Parker
Dam had only 39 percent POW Both tailwaters also
had the highest percentage of the >25-µm size-
fraction as POM (Davis: 60 percent and Parker: 50
percent). The proportion of organic material in the
samples decreased from upstream to downstream
(table 11) and reached a low of only 7 percent at
Yuma. This trend was most apparent in the total dry-
weight category (inorganic and organic matter)
where all size-fractions were combined.
Table 12 presents the summary results for the total
particulate matter sampled during phase 1. The data
include range, mean, and standard deviation for the
total particulate matter as well as the inorganic (ash-
weight) and organic (POM) portions. Both total dry
weight (inorganic and organic) and total ash weight
(inorganic) showed generally increasing values
proceeding from Davis Dam downstream to Yuma.
Table 11.-Percentage of POM to dry weight, POM/DW,
for each size-fraction and total sample for phase 1
(Oct. 1986 to June 1987).
<25 µm >25 µm Total,
Station* POM/DW
Davis Dam 33 60 61
Park Moabi 38 6 29
Parker Dam 37 50 39
Headgate Rock Dam 27 9 23
Palo Verde Diversion
Dam 18 3 16
Cibola 24 4 12
Imperial Dam 14 2 8
Yuma 15 2 7
* Number of samples at all stations is 8.
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