**National Irrigation Water Quality Program**\
U.S. Department of the Interior

**Reconnaissance Investigation of Water Quality, Bottom Sediment, and
Biota Associated with Irrigation Drainage in the Gunnison and
Uncompahgre River Basins and at Sweitzer Lake, West-Central Colorado,
1988-89**

David L. Butler, U.S. Geological Survey\
Richard P. Krueger, U.S. Fish and Wildlife Service\
Barbara Campbell Osmundson, U.S. Fish and Wildlife Service\
Andrew L. Thompson, U.S. Fish and Wildlife Service\
Steven K. McCall, U.S. Bureau of Reclamation

ABSTRACT

During the last several years, there has been increasing concern about
the quality of irrigation drainage and its potential harmful effects on
human health, fish, and wildlife. This report describes the results of a
reconnaissance investigation done during 1988-89 of the Uncompahgre
Project, located in west-central Colorado. Water, bottom sediment, and
biota samples were collected in the Gunnison and Uncompahgre River
basins, and at Sweitzer Lake to identify potential water-quality
problems that could be associated with the Uncompahgre Project. The
Uncompahgre Project was selected for a reconnaissance investigation
because unusually large selenium concentrations have been reported in
the Gunnison River downstream from the project and in fish from Sweitzer
Lake.

Irrigation drainage from the Uncompahgre Project area contributes
dissolved solids, sodium, sulfate, nitrite plus nitrate, selenium,
boron, and uranium to the Gunnison and Uncompahgre Rivers. Selenium
concentrations in some of the water samples collected from both rivers
exceeded U.S. Environmental Protection Agency criteria for protection of
aquatic life and the concentrations may be of concern for fish and
waterfowl because of food-chain bioconcentration. The largest
concentration of selenium from the Gunnison River was 10 micrograms per
liter in a sample collected in July 1988 upstream from Escalante Creek.
The largest selenium concentrations in the Uncompahgre River were in
samples collected at Delta; concentrations were 33 micrograms per liter
in November 1987 and 34 micrograms per liter in January 1988. The
insecticide parathion was detected at concentrations exceeding the
criteria for protection of aquatic life in both the Gunnison and
Uncompahgre Rivers in samples collected in July 1988.

Irrigation-drainage water discharging into Sweitzer Lake contributes
dissolved solids, sodium, sulfate, nitrite plus nitrate, and\
selenium to the lake during the nonirrigation season. The maximum
concentrations of dissolved solids, sodium, sulfate, selenium, boron,
and uranium were in samples collected during January and March 1988 from
the Garnet Canal diversion at Sweitzer Lake; selected maximum
constituent concentrations were: 12,700 milligrams per liter of
dissolved solids, 320 micrograms per liter of selenium, 800 micrograms
per liter of boron, and 64 micrograms per liter of uranium. Water in the
Garnet Canal during the nonirrigation season probably is
irrigation-drainage water.

Concentrations of selenium in four sets of water samples collected in
Sweitzer Lake ranged from 10 to 25 micrograms per liter. The selenium
concentrations in all water samples collected at Sweitzer Lake exceeded
criteria for protection of aquatic life. Mercury was detected in water
samples collected from the lake and from inflow into the lake in July
1988.

Concentrations of selenium in bottom-sediment samples collected from the
Gunnison and Uncompahgre Rivers were slightly greater than baseline
concentrations for soils in the Western United States. There was
substantially more selenium in bottom sediments from Sweitzer Lake; the
selenium concentration was 41 micrograms per gram in a sample collected
in January\
1988.

Selenium concentrations in fish and avian food items at Sweitzer Lake
may be large enough for fish and wildlife to accumulate harmful amounts
of selenium through biomagnification of selenium in the food chain.
Selenium concentrations in all whole-body fish samples from Sweitzer
Lake exceeded the 85th-percentile concentration of the National
Contaminants Biomonitoring Program. The Maximum selenium concentration
was 50 micrograms per gram dry weight in a carp sample from Sweitzer
Lake. The maximum recommended daily intake of selenium for humans could
be exceeded by eating catfish from Sweitzer Lake; three ounces of
catfish fillet had about 502 micrograms of selenium.

Concentrations of selenium in many whole-body samples from the Gunnison
and Uncompahgre Rivers and three tributaries of the Uncompahgre River
exceeded the 85th-percentile concentration of the National Contaminants
Biomonitoring Program. The maximum selenium concentration in a fish
sample collected from streams was 10.5 micrograms per dry weight in a
carp collected from Dry Creek, a tributary of the Uncompahgre River.

Selenium concentrations in bird livers, whole-body birds, and eggs
collected at Sweitzer Lake and the Escalante State Wildlife Area were
equal, and some of the selenium concentrations indicate significant
exposure to selenium. The maximum selenium concentration in a bird
sample was about 84 micrograms per gram dry weight in the liver of a
western grebe collected at Sweitzer Lake.

Most other trace-element concentrations were less than baseline
concentrations or less than concentrations that might be harmful to fish
and wildlife. There were concentrations of cadmium, copper, mercury, and
zinc in some biota samples that exceeded background concentrations.
Large concentrations of mercury were reported in two common merganser
livers collected at the Escalante State Wildlife Area.

DDE was detected in all biota samples that were analyzed for organic
compounds. The maximum DDE concentration was 110 micrograms per gram wet
weight in a whole-body killdeer that probably accumulated the DDE in its
wintering areas outside of Colorado. Toxaphene was detected in 12 biota
samples. Concentrations of the herbicide dacthal in three fish samples
exceeded the maximum dacthal concentration reported by the National
Pesticide Monitoring Program.

The Colorado River downstream from the Gunnison River provides habitat
for endangered fish and birds. The Uncompahgre Project area is a major
source of selenium to the Gunnison River; the effects of the selenium on
the endangered fish and birds are not known.