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

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

By Norman E. Spahr and Robert W. Boulger

Abstract

Quality-control samples provide part
of the information needed to estimate the bias
and variability that result from sample collection,
processing, and analysis. Quality-control samples
of surface water collected for the Upper Colorado
River National Water-Quality Assessment study
unit for water years 1995-96 are presented and
analyzed in this report. The types of quality-
control samples collected include pre-processing
split replicates, concurrent replicates, sequential
replicates, post-processing split replicates, and
field blanks.
Ana]ysis of the pre-processing split repli-
cates, concurrent replicates, sequential replicates,
and post-processing split replicates is based on
differences between analytical results of the envi-
ronmental samples and analytical results of the
quality-control samples. Results of Ihese compari-
sons indicate that variability introduced by
sample collection, processing, and handling is
low and will not affect interpretation of the envi-
ronmental data. The differences for most water-
quality constituents is on the order of plus or
minus I or 2 lowest rounding units. A lowest
rounding unit is equivalent to the magnitude of
the least significant figure reported for analytical
results. The use of lowest rounding units avoids
some of the difficulty in comparing differences
between pairs of samples when concentrations
span orders of magnitude and provides a measure
of the practical significance of the effecI of
variability.

Analysis of field-blank quality-control
samples indicates that with the exception of chlo-
ride and silica, no systematic contamination of
samples is apparent. Chloride contamination
probably was the result of incomplete rinsing of
the dilute cleaning solution from the outlet ports
of the decaport sample splitter. Silica contamina-
tion seems to have been introduced by the blank
water. Sampling and processing procedures for
water year 1997 have been modified as a result
of these analyses.

INTRODUCTION

The Upper Colorado River study unit (UeOL)
is I of 59 National Water-Quality Assessment
(NA WQA) study units. The long-tenn goals of
the NA WQA program are to (I) describe current
water-quality conditions for a large part of the
Nation's freshwater streams. rivers, and aquifers;
(2) describe how water quality is changing over time;
and (3) improve understanding of the primary natural
and human factors that affect water-quality conditions
(leahy and others, 1990). Hydrologic and water-
quality assessments of the UCOL slUdy unit began in
1994. The VeOl study unit is described by Driver
(1994) and Apodaca and others (\996). A network of
14 surface-water-quality sampling stations has been
established in the UeOl study unit (Spahr and others,
1996). Sampling for water-quality constituents began
at three of these sites in water year 1995, and full
implementation of sampling began in water year 1996.
Site locations are shown in ligure J. Site names and
station numbers are listed in ~1ble l. The NA WQA

Abstract