8180

• UCREFRP Catalog Number: 8180
• Author: Hamilton, S. J.
• Title: Hypothesis of Historical Effects From Selenium on Endangered Fish in the Colorado River Basin.
• USFW Year: 1999.
• USFW - Doc Type: \
• Copyright Material: YES

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Human and Ecological Risk Assessment: Vol. 5, No.6, pp. 115~1l80 (1999)

Hypothesis of Historical Effects From Selenium
on Endangered Fish in the Colorado River Basin

Steven J. Hamilton
U.S. Geological Survey, Biological Resources Division, Yankton, South
Dakota 57078-6364*

ABSTRACT

Anthropogenic selenium contamination of aquatic ecosystems was first
associated with cooling reservoirs of coal-fired power plants in the late 1970s,
and later with drainage water from agricultural irrigation activities in the
1980s. In the 1990s, selenium contamination has been raised as a concern in
the recovery of currently endangered fish in the Colorado River system.
Widespread contamination from seleniferous drain waters from agriculture
has been documented in the upper and lower Colorado River basins. Histori-
cally, irrigation started in the upper Colorado River basin in the late 1880s. In
the 1930s, selenium concentrations in various drains, tributaries, and major
rivers in the upper and lower Colorado River basins were in the 100s and 1000s
of Ilg/L. Native fish inhabiting large rivers such as the Colorado pikeminnow
and razorback sucker were abundant before 1890, but became rare after 1910
to 1920, before the influence of mainstem reservoirs in the upper and lower
Colorado River. A hypothesis is presented that selenium contamination of the
tributaries and major rivers 'of the Colorado River basin in the 1890 to 1910
period caused the decline of the endangered fish and continues to inhibit
their recovery.

Key Words: Colorado River, Gunnison River, endangered fish, Colorado
pikeminnow, razorback sucker, bony tail , irrigation, drainage,
selenium

*

U.s. Geological Survey, Biological Resources Division. Columbia Environmental
Research Center, Ecotoxicology Research Station, 31247 436th Avenue, Yankton,
South Dakota 57078-6364; Tel: [phone]; Fax [phone]; E-mail:
steve [e-mail]

1080-7039/99/$.50
@ 1999 by ASP