**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 Pine River Project
Area, Southern Ute Indian Reservation, Southwestern Colorado and
Northwestern New Mexico, 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\
James J. Formea, Bureau of Indian Affairs\
Donald W. Wickman, Bureau of Indian Affairs

ABSTRACT

The U.S. Department of the Interior has completed 20 reconnaissance
investigations in the Western United States to determine if irrigation
drainage has the potential to affect human health, fish, and wildlife or
has adversely affected the suitability of water for other beneficial
uses. A reconnaissance investigation of the Pine River Project, which is
drained primarily by the Los Pinos River (also known as the Pine River)
in southwestern Colorado, was initiated in 1988. Water, bottom sediment,
and biota were sampled and analyzed during 1988-89 to determine if
selenium or other potentially harmful constituents were present in the
Pine River Project area. Soil and plant samples were collected from the
Oxford Tract in 1989 to determine the magnitude and variability of
selenium on the tract. The Oxford Tract is a block of Indian land where
problems concerning human health and livestock caused by selenium
poisoning have been documented.

Irrigation drainage does not seem to be a major source of dissolved
solids to streams in the Pine River Project area. The maximum
dissolved-solids concentration in the Los Pinos River was 156 milligrams
per liter; concentrations in tributaries and other streams receiving
irrigation drainage ranged from 89 to 1,090 milligrams per liter.
Concentrations of manganese in 25 samples and mercury in 1 sample
exceeded the maximum recommended level in the U.S. Environmental
Protection Agency drinking-water regulations. Ground water from
nonirrigation sources may be contributing manganese to streams. The
maximum concentration of mercury in a water sample was 2.3 micrograms
per liter from the reference site on the Los Pinos River. The
concentration of selenium exceeded the maximum-contaminant level (50
micrograms per liter) in only one surface-water sample. Concentrations
of selenium in 12 surface-water samples exceeded the U.S. Environmental
Protection Agency\'s chronic criterion for selenium for protection of
aquatic life (5 micrograms per liter). The maximum selenium
concentration in a surface-water sample was 94 micrograms per liter from
Rock Creek on the Oxford Tract, an area known to have large selenium
concentrations in ground water. Irrigation drainage probably is
contributing some of the selenium to Rock Creek and other streams in the
Pine River Project area. Selenium concentrations in the Los Pinos River
and in Navajo Reservoir were less than or equal to 1 microgram per
liter.

Selenium concentrations in 8 of 10 ground-water samples collected at 5
sites were much larger than 50 micrograms per liter. The maximum
concentration was 4,800 micrograms per liter in a sample from a well
located in a nonirrigated area west of the Pine River Project. Water
levels measured in two wells near irrigated areas indicate a definite
connection between irrigation application and shallow ground water in
parts of the Pine River Project area.

Trace-element concentrations in bottom sediment in the Pine River
Project area generally were within baselines for soils and within
concentration ranges reported for previous reconnaissance
investigations. All selenium concentrations determined in
bottom-sediment samples were less than 1 microgram per gram.

Results of analyses of soil samples from the Oxford Tract indicated that
areas previously or presently (1989) irrigated had significantly greater
concentrations of total selenium and extractable selenium in soil than
did areas that were never irrigated. Total selenium concentrations in 66
plant samples collected on the Oxford Tract were extremely variable; the
maximum concentration was 1,500 milligrams per kilogram in a snakeweed
sample. A number of forage plant samples, including alfalfa, had large
total selenium concentrations. One alfalfa sample had 180 milligrams per
kilogram of selenium.

Selenium is the trace element of greatest concern in biota in the Pine
River Project area. Most of the whole-body fish samples had selenium
concentrations that exceeded the National Contaminant Biomonitoring
Program 85th percentile; however, concentrations were less than the
selenium concentrations known to cause reproductive problems in fish.
There was no significant difference between selenium concentrations in
whole-body fish samples collected upstream and downstream from irrigated
areas. Selenium concentrations in aquatic plants, aquatic invertebrates,
and small mammals may be sufficiently large to be of concern because of
possible food-chain bioconcentration. Maximum concentrations of selenium
were 10.2 micrograms per gram dry weight in an aquatic insect sample and
23 micrograms per gram dry weight in a prairie dog sample.

Bird samples collected at two wetland sites on the Oxford Tract had
significantly larger selenium concentrations than bird samples collected
at two wetland sites along the Los Pinos River. Maximum selenium
concentrations in bird samples collected on the Oxford Tract were 50.0
micrograms per gram dry weight in a liver sample and 49.0 micrograms per
gram dry weight in a whole-body sample. Two samples of mallard breast
tissue collected on the Oxford Tract has selenium concentrations that
exceeded guidelines for human consumption. The primary source of
recharge to the wetlands on the Oxford Tract is irrigation water.

Cadmium concentrations in about 30 percent of whole-body fish samples
and copper concentrations in nearly one half of whole-body fish samples
exceeded the National Contaminant Biomonitoring Program 85th percentiles
of 0.05 and 1.0 microgram per gram wet weight, respectively. However,
these concentrations are considered too small to have toxic effects.
There was no significant difference between copper concentrations in
whole-body fish samples collected upstream and downstream from irrigated
areas. Two whole-body fish samples had lead concentrations that exceeded
the 85th percentile for lead (0.22 microgram per gram wet weight) and
also exceeded a guideline for lead in foods consumed by humans.

Concentrations of mercury in 16 whole-body fish samples collected in the
Pine River Project area during 1988-89 exceeded the 85th percentile for
mercury (0.17 microgram per gram wet weight). Ten of these samples were
collected from Navajo Reservoir. The maximum mercury concentration in
whole-body fish samples was 1.3 micrograms per gram dry weight in a
channel catfish from the Los Pinos River at La Boca and in a common carp
from the Piedra River arm of Navajo Reservoir. Nine whole-body fish
samples and one channel-catfish fillet sample had mercury concentrations
that equaled or exceeded 0.25 microgram per gram wet weight, which is a
guideline for consumption of fish by pregnant women. The only
organochlorine pesticides detected in fish and bird samples were
p,p\'-DDE and mirex. Organochlorine pesticide concentrations were less
than adverse-effect levels reported in the literature.