WSP02811

• File Number: 8200.766
• Description: Gunnison River General
• State: CO
• Basin: Gunnison
• Water Division: 4
• Date: 1/1/1991
• Author: USGS
• Title: Reconnaissance Investigation of Water Quality-Bottom Sediment-and Biota Associated with Irrigation Drainage - Gunnison and Uncompahgre River Basins and Sweitzer Lake - West Central Colorado
• Water Supply Pro - Doc Type: Report/Study

!JO~3~3

Table 3.--summary of selected water-quality data for samples collected
from alluvial aquifers and aquifers in the Dakota Sandstone
in the Uncompahgre River valley

[Analyses by U.S. Geological Survey; concentrations are in micrograms per
liter, except for dissolved solids and nitrate as nitrogen, which are
in milligrams per liter; all constituents are dissolved unless noted;
<, less than; not determined. Data-collection period is 1974-82]

Constituent Nll!Dber of Median Maximum Minimum
samples
Dissolved solids 14 1,080 12 , 400 347
Nitrate as nitrogen 14 .12 20 .00
Arsenic 7 1 270 <1
Arsenic, total 5 3 3 2
Boron 12 260 12,000 50
Cadmium 6 <2 0
Chromium 6 10 10 0
Copper 6 1 6 <1
Iron 14 120 1,800 <10
Lead 6 1 2 0
Manganese 14 21 1,300 <10
Mercury 6 <.1 0
Selenium 7 <I 21 0
Selenium, total 5 5 15 <I
Sil ver 6 <1 0
Zinc 6 20 300 5

In 1986, the U.S. Bureau of Reclamation sampled water flowing from an
abandoned gas well located along the banks of the Gunnison River a few miles
upstream from Delta. The volume of water flowing from the well was small and
fluctuated considerably. The water was a brine that had large concentrations
of arsenic, boron, lead, mercury, selenium, strontium, and vanadium. Source
of water from this well is unknown.

Soil and Bottom-Sediment Data

Geochemical data for soils in the Delta and Grand Junction areas were
available from the U.S. Geological Survey (T.F. Harms, U.S. Geological Survey,
written commun., 1988). Only certain elements were analyzed in those samples,
and selenium was not determined in the soil samples from the Delta area.
There were geochemical data for certain elements for 28 soil samples that were
collected from irrigated areas in the Grand Valley (Grand Junction area,
fig. 1). Soils and climate in the Grand Valley are similar to soils and
climate in the Delta area. A statistical summary of the geochemical data for
the soil samples is listed in table 5. Two rock samples from the Mancos
Shale (one near Delta and one near Grand Junction) had 3 and 2 ~g/g selenium

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