**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 Middle Arkansas River
Basin, Colorado and Kansas, 1988-89

David K. Mueller, U.S. Geological Survey\
Lawrence R. DeWeese, U.S. Fish and Wildlife Service\
A. Jack Garner, U.S. Bureau of Reclamation\
Timothy B. Spruill, U.S. Geological Survey

ABSTRACT

During the last several years, concern by the U.S. Department of the
Interior has been increasing about the potential effects of irrigation
drainage on the health of humans, fish, and wildlife. During 1988, a
reconnaissance investigation was made of irrigation-drainage quality in
the middle Arkansas River basin in southeastern Colorado and
southwestern Kansas. This area was selected because high concentrations
of selenium previously had been detected at several sites on the
Arkansas River and its tributaries. This investigation was part of a
program initiated in 1985 by the U.S. Department of the Interior to
evaluate the effects of irrigation drainage on water quality, bottom
sediment, and biota in the Western United States.

Water, bottom-sediment, and biota samples were collected at 14
surface-water sites\--7 sites on the Arkansas River, 2 sites on the
tributary streams, and 5 sites on reservoirs. Ground-water samples were
collected from five municipal wells completed in the Arkansas River
valley alluvial aquifer.

Drainage from irrigated land underlain by marine shale affects the
Arkansas River between La Junta, Co., and Deerfield, KS.; two tributary
streams in the vicinity of Pueblo, Co.; and several off-channel
reservoirs. Selenium was the only trace constituent associated with
irrigation drainage that was detected at elevated concentrations in
water, bottom sediment, and biota.

Selenium concentrations in surface water ranged from 1 microgram per
liter, in Pueblo Reservoir near the upstream end of the study area in
Colorado, to 52 micrograms per liter in the St. Charles River near
Vineland, Co. The maximum concentration detected in alluvial ground
water was 29 micrograms per liter at Las Animas, Co. State
drinking-water standards and the U.S. Environmental Protection Agency
maximum contaminant level for selenium (10 micrograms per liter) were
exceeded at three stream sites and three ground-water sites. State
aquatic-life standards and the U.S. Environmental Protection Agency
criterion for acute exposure to selenium were not exceeded at any sites
on the Arkansas River or in any reservoirs. However, the Colorado
standard for chronic exposure and the U.S. Environmental Protection
Agency criterion for chronic and acute exposure were exceeded in two
tributary streams. The U.S. Environmental Protection Agency criterion
for chronic exposure was exceeded at four sites on the Arkansas River
and in three reservoirs.

Elevated concentrations of selenium in bottom sediment occurred at four
of five reservoir sites and at one tributary site. The maximum
concentration was 5.4 micrograms per gram in Lake Meredith near Ordway,
Co.

Geometric mean selenium concentrations in livers from bird species
collected at reservoirs during the spring were highest in killdeer (9.9
to 42 micrograms per gram dry weight), intermediate in mallards (9.7 to
24 micrograms per gram), and lowest in American coots (12 to 15
micrograms per gram). The maximum selenium concentration (56 micrograms
per gram) was detected in the liver of a black-necked stilt from Lake
Meredith in Colorado.

Five species of fish from the Arkansas River had selenium concentrations
ranging from 2.1 to 18.5 micrograms per gram dry weight, and three
species from the tributaries had selenium concentrations ranging from
3.6 to 16.9 micrograms per gram. Thirteen species of fish in the
reservoirs had selenium concentrations ranging from 2.2 to 20 micrograms
per gram. Selenium concentrations in invertebrates from the Arkansas
River, tributaries, and reservoirs ranged from 2.7 to 8.7 micrograms per
gram. The maximum concentration of selenium detected in plants was 14
micrograms per gram in a sample of algae from Lake Meredith in Colorado.
Eight organochlorine pesticides were detected in some samples of bird
livers and eggs and in fish from the reservoirs, but all concentrations
were within the ranges of reported background concentrations. No
evidence of deformity or reproductive failure was observed for any bird
or fish species; however, the study was not designed to assess
reproduction or to determine the extent of embryonic deformities.

Selenium concentrations in some samples of food organisms (small fish,
invertebrates, and aquatic plants) exceeded the dietary concentration of
10 micrograms per gram wet weight demonstrated to alter reproduction in
mallards. Nearly all fish samples had selenium concentrations exceeding
the 85th percentile established by a national survey. Nearly all fish
samples from three reservoirs and almost none from two other reservoirs
had whole-fish concentrations of selenium exceeding the concentration
that correlated with reproductive impairment in bluegills.

Selenium concentrations in fish collected from reservoir sites were
positively correlated to selenium concentrations in the reservoir water.
No other relations between abiotic and biotic matrices were identified.

Elevated concentrations of aluminum, arsenic, copper, lead, mercury, and
zinc also were determined in at least one matrix (water, sediment, or
biota) at one or more sites. The source of lead, mercury, and zinc may
be mine drainage upstream from the study area.