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

The difference in chloride values for the Gunnison
near Grand Junction site also is -0.1 mglL (table 4),
but the percent difference is only -1.4. The lowest
rounding unit difference for both pairs of samples
is -1. The practical variability (measure of difference
between environmental and split-replicate samples due
to sample process, handling, shipping, and analysis) is
equivalent for both sets of samples.

Pre-Processing Split Replicates

Pre-processing split-replicate sampling for
general chemical constituents, nutrients, and trace
elements involves the collection of twice the normal
volume of water that is needed for a typical water
sample. The water is split into two samples-a typical
water-quality sample (termed the environmental
sample) and a pre-processing split-replicate sample.
Pre-processing split-replicate sampling for dissolved
and suspended organic carbon involves collecting
two separate samples (the environmental and
pre-processing split-replicate sample). Each sample
is then 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 pre-processing split-replicate sample
is processed. The split-replicate sample is processed
using a new filter and clean equipment. Comparison
of results between the environmental samples and
the split-replicate samples provides an indication
of the variability associated with sample processing,
handling, shipment, and analysis. During water
years 1995-96, seven pairs of environmental and
split-replicate samples were collected. The distribution
of collection of the split-replicate samples by date and
site is shown in figure 2.

Comparison of General Chemical Constituents

Results of comparison of the environmental and
the pre-processing split-replicate samples for general
chemical constituents are listed in table 4. The differ-
ences between the environmental and split-replicate
values are given in the units of the constituent and in
units termed lowest rounding unit.

GUNNISON NEAR
GRAND JUNCTION

GORE

(f) UNCOMPAHGRE
W
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(f)
CJ
Z FRENCH
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c...
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<(
(f) DRY

DRY FORK

o

o

o

o

o

J F M A M J

SON D
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BAKER

FMAMJJA

1995

JASONDJ
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1996

Figure 2. Distribution of collection of pre-processing split-replicate samples, 1995-96.

DATE

6 Interim Results of Quality-Control Sampling of Surface Water for the Upper Colorado River National Water-Quality
Assessment Study Unit, Water Years 1995-96