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

Field Screening of Water Quality, Bottom Sediment, and Biota Associated
with Irrigation Drainage, Wind River Indian Reservation, Wyoming,
1992-93

Dennis N. Grasso, U.S. Geological Survey\
Mary E. Jennings, U.S. Fish and Wildlife Service\
Wilfrid J. Sadler, U.S. Geological Survey

ABSTRACT

Physical, chemical, and biological data were collected in 1992 and 1993
from irrigation drainage areas and wetlands of the Wind River Federal
Irrigation Project, Wind River Indian Reservation, Wyoming. In this
semiarid area of Wyoming, the natural and irrigation-impacted wetlands
of the reservation are attractive to migratory and nesting aquatic
birds, several species of fish, and three federally listed endangered
species\--bald eagles, peregrine falcons, and whooping cranes\--that are
know to use these wetland habitats seasonally. In response to increasing
concern about the quality of irrigation drainwater and its potential
adverse effects on fish, wildlife, and human health, an interagency
field screening was conducted by the U.S. Geological Survey and the U.S.
Fish and Wildlife Service, in cooperation with the Shoshone Tribe and
Northern Arapahoe Tribe. This study was conducted under the guidance of
the U.S. Department of the Interior National Irrigation Water Quality
Program.

Most samples collected from irrigated sites in the Wind River Federal
Irrigation Project had concentrations of inorganic constituents and
organic compounds less than reported levels of concern in water, bottom
sediment, and biota. However, in the Little Wind Unit irrigation area
between Fort Washakie and Arapahoe, concentrations of Selenium and
mercury in water exceeded the U.S. Environmental Protection Agency\'s
aquatic-life criterion for selenium, 5 µg/L (micrograms per liter), and
the proposed 1985 mercury criterion for freshwater aquatic life
protection (0.012 µg/L, 4-day average, not to exceed 2.4 µg/L on an
hourly average.) Of the 14 water samples analyzed from the Little Wind
Unit in 1993, 6 samples had selenium concentrations that equaled or
exceeded 5 µg/L, and 1 sample from McCaskey Drain had a selenium
concentration of 17 µg/L. Mercury concentrations in water sampled in the
study area during 1992-93 were 0.1 µg/L or less, except at four sites.
One water sample collected in 1993 from Sharp Nose Draw in the Little
Wind Unit had a mercury concentration of 4.0 µg/L, and three samples
collected in 1992 from Little Wind Unit and Johnstown Unit had mercury
concentrations of 0.2 µg/L. Natural concentrations of mercury in rivers
and lakes have been reported to range from 0.01 to 0.05 µg/L, and
concentrations of 0.1 to 2.0 µg/L have been reported to be fatal to
sensitive aquatic species.

Bottom-sediment samples from Goose Pond and Sharp Nose Pond in the
Little Wind Unit had selenium concentrations of 7.5 and 0.4 µg/g
(micrograms per gram). Mercury concentrations in the study area were
less than 0.02 µg/g at all bottom-sediment sampling sites investigated,
except for Sharp Nose Pond in the Little Wind Unit where a mercury
concentration of 0.02 µg/g was measured.

Selenium concentrations in some aquatic vegetation and invertebrates,
fish, bird eggs, and bird livers collected from the Little Wind Unit
also were greater than established levels of concern. At Goose Pond and
Sharp nose Pond, for example, selenium concentration in bird livers
ranged from 13.9 to 22.9 µg/g and 6.93 to 14.0 µg/g, with five of the
six samples collected exceeding the 10.0 µg/g level associated with
reproductive failure in aquatic birds. Of the biota samples collected
from the Little Wind Unit in 1993, no samples had concentrations of
mercury greater than levels known to cause adverse effects to sensitive
aquatic species. Mercury concentrations of 3.60 to 5.10 µg/g in the
livers of birds sampled from Sharp Nose Pond were greater than reported
levels in dietary items for the protection of sensitive species of
mammals and birds that regularly consume fish and other aquatic
organisms.