**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 Owyhee and Vale
Projects, Oregon and Idaho, 1990-91

Frank A. Rinella, U.S. Geological Survey\
William H. Mullins, U.S. Fish and Wildlife Service\
Carol A. Schuler, U. S. Fish and Wildlife Service

ABSTRACT

A reconnaissance investigation was conducted during 1990-91 in the
Owyhee and Vale projects in eastern Oregon and southwestern Idaho, as
well as at a number of sites in the Snake River and tributaries to the
Snake River in the area of study. The objective of the study was to
determine if agricultural drainwater entering the study area was
causing, or had the potential to cause, significant harmful effects to
human health, fish and wildlife, or may adversely affect the suitability
of water for beneficial uses.

Approximately 153,000 acres of land are irrigated annually within the
areas of the Owyhee and Vale projects. Large quantities of water are
required because of the semiarid climate and relatively high evaporation
rates. Several reservoirs in the area are filled annually during the
wet, nonirrigation season to sustain irrigation during the dry summer
months. During the irrigation season, this impounded water, along with
direct diversions from the Malheur, Owyhee, and Snake Rivers, is
transported to the irrigated areas through a series of diversion
tunnels, siphons, canals, aqueducts, ditches, and drains. Major crops
grown in the area include sugar beets, alfalfa hay and other hay crops,
onions, and winter wheat. Minor crops include corn, potatoes, mint,
various seed crops, and fruit. In 1987, it was estimated that the
following amounts of pesticides were used in the project areas: 2,4-D
(21,000 lbs \[pounds\]), chlorpyrifos (1,000 lbs), dacthal (40,000 lbs),
dicamba (320 lbs), endosulfan (2,500 lbs), ethion (11,000 lbs),
malathion (24,000 lbs), parathion (5,000 lbs), and phorate (11,000 lbs).

Median concentrations and values for total dissolved solids, alkalinity,
sodium adsorption ratio, and hardness in the Vale project area were
greater than 1.5 times those values observed in the Owyhee project area
or at other Snake River locations. During irrigation (August 1990),
total dissolved solids, alkalinity, sodium adsorption ratio, and
hardness values increased in a downstream manner. Constituent values at
drainwater sites generally were comparable to concentrations below the
irrigated areas in the Owyhee and Vale project areas.

The trace elements arsenic, boron, copper, molybdenum, vanadium, and
zinc were detected in most water samples; cadmium, chromium, lead, and
selenium were detected in some samples at concentrations generally near
the analytical reporting limit; mercury was not detected in any samples.
In some water samples, concentrations of arsenic, boron, cadmium,
copper, and lead exceeded State or Federal water-quality standards or
criteria.

Most trace elements in bottom sediment were detected at concentrations
within the expected 95-percent baseline range for soils from the Western
United States. Concentrations that exceeded the 95-percent baseline
range for study area soils were: (1) arsenic and lead in one sample from
a site in the Vale project area; (2) mercury, lead, and tin in one
sample from a site in the Snake River system; (3) manganese in two
samples from two sites in the Snake River system; and (4) manganese from
one sample from a site in the Vale project area.

Fifteen pesticides and metabolites were detected in whole-water samples
collected from 11 sites in the study area. DDT, plus its metabolites
(DDE and DDD), dieldrin, endrin, 2,4-D, dicamba, and dacthal were
detected in samples collected from seven or more sites. Other pesticides
detected included chlorpyrifos, endosulfan, ethion, malathion,
parathion, phorate, and lindane. Most of the detected pesticide
concentrations generally were largest in drainwater and at the most
downstream sampling locations in the Owyhee and Vale project areas.
Concentrations exceeded water-quality criteria established for the
protection of freshwater aquatic life in 86 percent of the whole-water
samples analyzed for DDT plus its metabolites, 71 percent of the
dieldrin samples, 14 percent of the endrin samples, and 10 percent of
the parathion samples.

Eight pesticides and metabolites were detected in bottom-sediment
samples collected from 14 sites in the study area. Chlordane, DDT plus
its metabolites, and dieldrin were detected at 11 or more of the sites.
Other pesticides or metabolites detected included aldrin, endosulfan,
and heptachlor epoxide. When normalized for organic-carbon
concentrations, concentrations for most of the eight compounds were
largest in drainwater and at the most downstream locations in the Owyhee
and Vale project areas. All bottom-sediment samples analyzed for
chlordane, DDT plus its metabolites, and heptachlor epoxide; about 50
percent of the endosulfan samples; and about 8 percent of the aldrin
plus dieldrin samples contained interstitial-water concentrations that
exceeded the \"no effect\" (safe) criteria proposed for the protection
of benthic fauna from chronic toxicity.

Concentrations of boron, mercury, selenium, cadmium, copper, lead, zinc,
and some organochlorine pesticides (DDT and its metabolites, dieldrin,
and toxaphene) in some biological tissues exceeded recommended
guidelines or criteria for the protection of the health of humans, fish,
or wildlife. However, these elevated concentrations were not
consistently found in all sample media or at all sampling sites.

Chemical and biological data collected during this reconnaissance
investigation were not conclusive as to whether irrigation\
drainage from the Owyhee and Vale project areas has caused or has the
potential to cause harmful effects on human health, fish, and wildlife.
Concentrations of total dissolved solids, major ions, nitrate plus
nitrite, arsenic, boron, and selenium increased during the irrigation
period. These increases were detected from above to below the irrigated
areas in the Owyhee and Vale project areas, and may be the result of
irrigation of the agricultural areas. Elevated pesticide concentrations
detected in surface water and bottom sediment within agricultural drains
and below the irrigated areas, in the project areas, further indicate
that these concentrations result from current and (or) historical
application of pesticides to the irrigated agricultural areas. However,
results of the biological data collected during this investigation do
not support the findings of the water-chemistry or bottom-sediment data.
Contaminants in some of the biological tissues were sufficiently
elevated to exceed recommended guidelines for the protection of human
health, fish, and wildlife; however, these elevated concentrations were
not consistently found in all sample media or at all sites.