9409

• UCREFRP Catalog Number: 9409
• Author: Spahr, N. E. and R. W. Boulger.
• Title: Interim Results of Quality-Control Sampling of Surface Water for the Upper Colorado River national Water-Quality Assessment Study Unit, Water Years 1995-96.
• USFW Year: 1997.
• USFW - Doc Type: 97-4227,
• Copyright Material: NO

STATE LINE
0 CONCURRENT REPLICATES
CAMEO !:::. SEQUENTIAL REPLICATES 0
DOTSERO !:::.
en GUNNISON 0
W AT 32 ROAD
I-
en
(!) EAST 0 0
z
::::i
a..
:2 0
<( GORE
en
REED !:::.
BAKER
J F M A M J J A S 0 N D J F M A M J J A S o N D
1995 I 1996 I
DATE

Figure 3. Distribution of collection of concurrent- and sequential-replicate samples, 1995-96.

Concurrent and Sequential Replicates

Concurrent and sequential replicates differ
from the split replicates in that two separate samples
are collected from the river. In the concurrent repli-
cate, one sample is collected concurrently with the
environmental sample using a second collection
team or second set of collection equipment. In the
sequential replicate, a replicate is collected as close
in time as possible to the environmental sample. Each
sample is processed through all the normal steps of a
typical water-quality sample. For each step of sample
processing, the environmental sample is processed
first, and then the replicate sample is processed. The
replicate samples are processed using a clean filter
and equipment. The concurrent and sequential repli-
cates include all the potential sources for variation
as with the pre-processing split replicates as well
as the variation due to sample-collection technique
and short-term environmental variations in the river.
The distribution of collection of the concurrent and
sequential replicates by site and date is shown in
figure 3.
Seven concurrent- and three sequential-
replicate samples were collected during water
years 1995-96. The comparison of environmental
and concurrent-replicate samples and environmental

and sequential-replicate samples for general chemical,
nutrient, and organic carbon constituents is presented
in the following sections. Concurrent- and sequential-
replicate data for trace elements are not presented
because only one concurrent and no sequential repli-
cates for trace elements were collected.

Comparison of General Chemical Constituents

Results of comparison between environmental
and concurrent-replicate samples and between envi-
ronmental and sequential-replicate samples for general
chemical constituents are listed in table 9. A summary
of the differences between the environmental and the
concurrent-replicate samples for the constituents listed
in table 9 is given in table 10. The sequential-replicate
comparisons are not summarized because only three
samples are available. The majority of the differences
agree within plus or minus 1 lowest rounding unit with
the exception of laboratory specific conductance and
residue on evaporation. The majority of the conduc-
tance differences agree within plus or minus 2 lowest
rounding units. One-half of the differences for residue
on evaporation are within plus or minus 2 lowest
rounding units and probably indicate the precision of
the laboratory method. Shaded cells in table 9 repre-
sent differences greater than plus or minus 1 lowest

QUALITY-CONTROL SAMPLING PROGRAM 15