WSP05652

• File Number: 8273.300
• Description: Colorado River Basin Salinity Control - Federal Agency Reports - USGS
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1997
• Author: USGS
• 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
• Water Supply Pro - Doc Type: Report/Study

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 -t. 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 nonnal
volume of waler that is needed for a typical water
sample. The water is split into IWO 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 s;unples (the environmental and
pre-processing split-replicate sample). Each sample
is then processed through all the nomlal steps of a

typical water-quality sample. For each step of sample
processing. the environmenJaI sample is processed
first. and then the pre-processing split-replicate sample
is processed. The split-replicate sample is processed
using a new tllter 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 Ihe 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-replica Ie samples for general
chemical constiwents are listed in table 4. The differ-
ences between the environmental and split-replicate
values are given in the units of the constiwent and in
units termed lowesl rounding unit.

GUNNISON NEAR
GRAND JUNCTION
GORE 0
<fJ UNCOMPAHGRE 0
w
f--
Cii
C!J
Z FRENCH 0
::;
0..
::E
<{
<fJ DRY 0
DRY FORK 0

BAKER

JFMAMJ

I I () I
FMAMJJA

1-1
SON D
I

1995

JASONQJ
I

1996

Figure 2. Distribution of collection of pre-processing split-replicale 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