FLOOD06374

• County: Gunnison
• Community: Uncompahgre Valley
• Basin: Gunnison
• Title: Uncompahgre Valley Water Users Association
• Date: 1/1/1984
• Prepared By: CWCB
• Floodplain - Doc Type: Data ‎(general)‎

Chern-Nuclear Geotech in Grand Junction, Colorado,
for X .ray diffraction analyses and mineralogic analyses
of solid-phase samples. The authors also thank Roger
Fujii of the U.S. Geological Survey in Sacramento,
California, for the selenium-speciation analyses and for
his valuable technical support to this study.

SAMPLE COLLECTION AND ANALYSIS

Sampling Sites

Surface-water-sampling sites are listed in
tables I and 2. The types of samples collected (water,
bottom sediment, and biota) at each site are listed in
tables I and 2. Ground-water sites where chemical
samples were collected are listed in table 3. Tables 1-3
are in the "Hydrologic and Biological Data" section at
the back of this report. All sampling sites in the
Uncompahgre Project area are shown on plate I, and
sampling sites in the Grand Valley are shown on plate
2. Sites on the Gunnison River upstream from Escal-
ante Creek are shown on plate 1, and the lower site on
the Gunnison River at Whitewater is shown on plate 2.
Site ESC3 (table 2), not shown on plate 2, is located
about 3.4 mi north-northeast of site ESC2 (pI. 2).
The sites listed in tables 1 and 2 are ordered by
drainage basins or by geographical areas relative to the
irrigated areas. Much of the irrigation drainage from
the Uncompahgre Project discharges into the
Uncompahgre River or its tributaries; therefore, sites
on the Uncompahgre River are listed first in table 1.
The next group of sites listed in table 1 (sites WST
through CC2) are in tributary basins west of the
Uncompahgre River, followed by sites in tributary
basins east of the river (sites sac through GTP). The
next group of sites in table 1 are on the Gunnison River.
Sites CR through FRP in table 1 are in tributary basins
of the Gunnison River that are outside the irrigated area
of the Uncompahgre Project shown on plate 1. The
remainder of the sites in table I are in basins tributary
to the Gunnison River that drain irrigated areas of the
Uncompahgre Project.
In the Grand Valley, the largest extent of irrigated
area is in the western part of the valley west of Grand
Junction (pI. 2). Therefore, sites north of the Colorado
River and west of the Gunnison River confluence (sites
SC through LC2) are listed first in table 2. Sites RED
and LKG are located south of the Colorado River and
west of the Gunnison River confluence. The next
group of sites in table 2 (sites IW through CF2) are
north of the Colorado River and upstream from the
Gunnison River confluence. The next group of sites
listed in table 2 (sites OMD through OM4) are on
Orchard Mesa, which is south of the Colorado River

and upstream from the Gunnison River confluence.
The last group of sites in table 2 are data-collection
sites on the Colorado River, Plateau Creek, and on the
Gunnison River downstream from Escalante Creek.

Sampling Methods

Onsite measurements at surface-water-sampling
sites included stream discharge, specific conductance,
pH, water temperature, and dissolved oxygen. Water-
quality measurements were made using methods simi-
larto those described by Knapton (1985). Where sam-
ples were collected at USGS surface-water stations,
stream discharge was determined from the stage record
and the stage-discharge rating table. Otherwise, stream
discharge was measured using methods described by
Rantz and others (1982).
Water samples from streams and washes were
collected using depth-integrating samplers and the
equal-width method (Ward and Harr, 1990). At sites
that had insufficient depth or discharge, water samples
were collected from the centroid of flow or at several
verticals in a cross section using l-L plastic or glass
bottles. Surface-water samples were composited in a
churn splitter. Water samples for insecticide analyses
were collected using bottles supplied by the USGS
National Water Quality Laboratory (NWQL) in
Arvada, Colorado. Water samples from ponds and wet-
lands were collected by wading into shallow areas and
collecting samples in a l-L bottle; the samples were
composited in a churn splitter.
Many of the wells used for ground-water sam-
pling were installed by the BOR as part of salinity
investigations (U.S. Bureau of Reclamation, 1986).
Five shallow observation wells were installed by the
USGS that were drilled using the hollow.stem auger
method. The wells were installed with 2-in. flush-
threaded PVC casings that had 5-ft screens and were
developed by purging approximately 30 well volumes.
Prior to collection of water samples, three to six well
volumes of water were purged using a centrifugal
pump. Water samples were collected from wells using
a Teflon bailer. Water in the bailer was carefully
decanted into clean, 4-L polyethylene bottles using a
bottom.emptying device to prevent sample agitation
and loss of volatile components (Barcelona and others,
1984). Onsite measurements at wells included water
level, specific conductance, pH, oxidation-reduction
potential (Eh), water temperature, dissolved oxygen,
and alkalinity. The Eh was measured using a platinum,
silver/silver-chloride reference electrode that was cali-
brated at least once daily using ZoBell's solution main-
tained at the ambient ground.watertemperature (Wood,
1976). Other meters were calibrated at least once daily,

4 Physlcol, Chemlcol, ond Blologlcol Dolo for Dolollod Study of IrrIgotlon Ilfolnoge In the Uncompahgre Project Areo ond
In the Grond Volley, W.ot..conlrol CoIorodo, 1991-82