**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 Columbia Basin Project,
Washington, 1991-92

S. S. Embrey, U.S. Geological Survey; E. K. Block

ABSTRACT

During a reconnaissance-level investigation in 1991-92, information was
collected to determine if irrigation drainage from the Columbia Basin
Project has caused or has potential to cause harmful effects on human
health or fish and wildlife, or might adversely affect the suitability
of water for beneficial uses. Results of the study generally indicated
no adverse effects on biota due to trace-element concentrations in
irrigation drainage. However, boron concentrations in aquatic plants
might affect water-fowl feeding on these plants. Also, arsenic
concentrations in coots were similar to those in mallards exhibiting
some abnormalities after being fed an arsenic-supplemented diet during
laboratory studies.

In surface water, concentrations of dissolved constituents were small
and with few exceptions did not exceed various standards or criteria
protecting humans, freshwater life, and beneficial uses of the water.
Dissolved solids, nitrate, boron, molybdenum, and vanadium
concentrations generally increased in a downstream directions
corresponding to water reuse throughout the Columbia Basin Project.
Concentrations also varied seasonally. During non-irrigation season
(November-March) when stream flows are sustained by return water from
tile drains and ground water, constituent concentrations tended to be
larger than during during irrigation season. During irrigation season
(April-October) concentrations are diluted by source water from the
Columbia River. During non-irrigation season dissolved solids exceeded
500 milligrams per liter and nitrate exceeded 10 milligrams per liter in
some wasteways in the southern part of the study area. Most of the types
of pesticides analyzed for in the 51 water samples were less than
analytical reporting limits. Of the pesticides detected, there were 18
detections of insecticides and 31 detections of herbicides, most of
which were observed in the July samples. The maximum observed dieldrin
concentration (0.014 micrograms per liter) exceeded the chronic
criterion for the protection of aquatic life. The herbicide 2,4-D was
detected in more samples than any other pesticide and in concentrations
as large as 1.0 microgram per liter.

In bottom sediment, many trace elements of interest were present only in
small concentrations near the analytical reporting limits. One selenium
concentration exceeded 4.0 micrograms per gram, a value of concern for
wildlife. Median concentrations of all trace elements of interest were
within the baseline range of concentrations for soils in the Western
United States. The maximum observed concentrations of selenium, uranium,
and manganese exceeded the upper value of the baseline range. Analyses
of bottom-sediment samples indicated that a variety of pesticides in
detectable concentrations are widespread throughout the study area; 19
of 21 samples had at least 1 detection of some insecticide. Dieldrin,
DDT, and DDE are still prevalent in much of the area. Methoxychlor,
which was applied for mosquito control, was found in samples from nine
of the sites in concentrations as large as 2.4 micrograms per kilogram.

In biota, particularly in a large percentage of fish, concentrations of
arsenic, boron, cadmium, chromium, and copper were elevated in some of
the samples compared with published standards, criteria, or baseline
values from other studies. In addition to fish, cadmium and copper
concentrations were elevated in some of the snail samples, and chromium
concentrations were elevated in pondweed. Elevated copper concentrations
in biota are probably due to copper sulfate used as an algicide in the
canals. Mercury and selenium were not elevated in biological tissues.
Organochlorine pesticides and related compounds were generally detected
in small concentrations. In fish samples collected from some wasteways,
concentrations of total chlordane, total DDT, and dieldrin exceeded
criteria for the protection of fish health and of fish-eating predators.
Compared with data collected in past years, total DDT concentrations in
carp and perch have shown little change with time. Concentrations of DDT
have declined little over the past 15 years, contrary to the significant
decline in concentrations of DDT compounds observed in nationwide
monitoring programs. Chlordane, detected only infrequently during past
years, was detected in about 70 percent of the 1992 samples. In
addition, chlordane concentrations observed in several fish samples were
about twice the historical maximum concentration of 0.07 micrograms per
gram. However, changes in laboratory methods and some differences in
sampling sites limit the accuracy in comparing these data sets over
time.

Other types of biological assessments used in this study indicated few
or no adverse effects to biota in the study area. Surface water was not
toxic to Daphnia magna and sediment bioassays showed moderate toxicity
to Chironomus tentans in 9 of 21 samples. External lesions in fish were
observed only infrequently; no abnormalities were observed in bird
embryos, and eggshell thicknesses of mallard and grebe eggs were similar
to those of the pre-DDT era.