9342

• UCREFRP Catalog Number: 9342
• Author: Wynn, K. H., N. J. Bauch and N. E. Driver.
• Title: Gore Creek Watershed, Colorado--Assessment of Historical and Current Water Quantitiy, Water Quality, and Aquatic Ecology, 1968-98.
• USFW Year: 2001.
• USFW - Doc Type: Denver.
• Copyright Material: NO

(SMCL), and proposed (PMCL) maximum contaminant
levels set for drinking water, and maximum contaminant
level goals (MCLG), drinking-water advisory (DWA),
and health advisory (RA) standards (U.S. Environmental
Protection Agency, 1996). The USEPA standards are
defined as the permissible level of a contaminant in
treated water delivered to users of a public water-supply
system, and as such, do not relate specifically to the
untreated water samples discussed in this report, except
as a point of reference. The lowest applicable stream-
quality standards are discussed, where applicable, in this
report; values were calculated for Gore Creek by Wynn
and Spahr (1998) using the methods of the Colorado
Department of Realth (1996). These standards are gener-
ally the chronic or acute aquatic-life standards for the
protection of aquatic life.
Data collection in the Gore Creek watershed
by the USGS since October 1995 has followed
published protocols for the USGS NAWQA Program.
The following information summarizes the sample-
collection protocols followed by the USGS for water,
sediment, and stream-biota data collection. Surface-
and ground-water samples were collected following
the protocols described by Shelton (1994) and Koterba
and others (1995), respectively. As part of the UCOL
NAWQA assessment of surface- and ground-water
quality, quality-assurance samples constituted no less
than 10 percent of the total number of environmental
samples. An interim report of surface-water quality-
control sample results is presented by Spahr and
Boulger (1997). Fish-community data for the mouth
of Gore Creek were collected by electroshocking
in a 450-ft stream reach near the mouth of Gore Creek,
using protocols described by Meador and others
(1993). Fish- and macroinvertebrate-tissue samples
were collected using the protocols described by
Crawford and Luoma (1994). Algae samples were
collected from rock surfaces in riffle areas using
the protocols described by Porter and others (1993).
Streambed-sediment samples were collected using
the protocols described by Shelton and Capel (1994).
Macroinvertebrate-community samples were collected
from riffle areas by using a 1-m2 hand screen equifped
with 425-1illl2 mesh material. Generally, 1 to 2 m
of substrate was sampled upstream from the hand
screen to collect a macroinvertebrate sample.
Macroinvertebrate-community abundance results
were normalized to the number of organisms per
square meter. Qualitative riparian and aquatic habitat
was scored using USEPA rapid bioassessment proto-
cols (RBP) described by Plafkin and others (1989).

Triplicate samples were collected at selected
sites for quality control of the algal-biomass and
algae- and macroinvertebrate-community sampling
in September 1997. Where triplicate samples were
collected, the values discussed and shown on graphs
represent the average value for that site. The standard
error of the mean (standard deviation divided by the
square root of the number of samples) was calculated
and included on graphs to show the variability of the
sample results. For example, in figure 25B, the error
bars overlain on the graphs represent the standard error
of the mean biovolume for nitrogen-autotroph diatom
for the two sites where triplicate algae samples were
taken for quality-control purposes. Short error bars
indicate less variability in sampling and processing
methods. For example, the biovolume at site 26 is
about 5.25x 107 1illl3tcm2 plus or minus the standard
error of 0.75x 107 1illl3tcm2. Because the standard
error at site 26 overlaps the measured algal biovolume
at site 18, one cannot say with confidence that algal
biovolume at site 26 is significantly lower than algal
biovolume at site 18.
Nutrient data for surface-water sites in the
Gore Creek watershed were identified and compiled
from several sources (table 1). Because the data were
collected by various groups for different purposes and
a variety of laboratory methods were used, nutrient
constituents were reported in numerous ways. The
available nutrient data included 24 nitrogen and phos-
phorus constituents that were collected at 30 sites
between February 21, 1968, and December 16, 1997
(fig. 7).
For the evaluation of nutrient conditions in
the Gore Creek watershed, nutrient constituents were
aggregated to reduce the number of constituents from
15 to 5. The procedures used to aggregate nutrient
constituents follow the method of Mueller and others
(1995) and are summarized in table 2. The data aggre-
gation resulted in the creation of a nutrient-analysis
data set that included the following constituents:

· ammonia nitrogen, as nitrogen (hereinafter referred
to as "ammonia");

· nitrate nitrogen, as nitrogen (hereinafter referred to
as "nitrate");

· total nitrogen, as nitrogen (hereinafter referred to as
"total nitrogen");

· orthophosphate, as phosphorus (hereinafter referred
to as "orthophosphate"); and

· total phosphorus, as phosphorus (hereinafter
referred to as "total phosphorus").

METHODS OF DATA REVIEW AND ANALYSIS 19