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

Detailed Study of Water Quality, Bottom Sediment, and Biota Associated
with Irrigation Drainage in the Klamath Basin, California and Oregon,
1990-92

Peter D. Dileanis, U.S. Geological Survey\
Steven E. Schwarzbach, U.S. Fish and Wildlife Service\
Jewel Bennett, U.S. Fish and Wildlife Service\
and others

ABSTRACT

The effect of irrigation drainage on the water quality and wildlife of
the Klamath Basin in California and Oregon was evaluated during 1990-92
as part of the National Irrigation Water Quality Program of the U.S.
Department of the Interior. The study focused on land serviced by the
Bureau of Reclamation Klamath Project, which supplies irrigation water
to agricultural land in the Klamath Basin and the Lost River Basin. The
Tule Lake and Lower Klamath National Wildlife Refuges, managed by the
U.S. Fish and Wildlife Service, are in the study area. These refuges
provide a critical resting and breeding habitat for waterfowl on the
Pacific flyway and are dependent on irrigation drainwater from upstream
agriculture for most of their water supply.

Water-quality characteristics throughout the study area were typical of
highly eutrophic systems during the summer months of 1991 and 1992.
Dissolved-oxygen concentrations and pH tended to fluctuate each day in
response to diurnal patterns of photosynthesis, and frequently exceeded
criteria for protection of aquatic organisms.

Nitrogen and phosphorus concentrations were generally at or above
threshold levels characteristic of eutrophic lakes and streams. At most
sites the bulk of dissolved nitrogen was organically bound. Elevated
ammonia concentrations were common in the study area, especially
downstream of irrigated land. Concentrations of ammonia in samples from
small drains on the Tule Lake refuge leaseland were higher than those
measured in the larger, integrating drains at primary monitoring sites.
The mean ammonia concentration in leaseland drains \[1.21 milligrams per
liter (mg/L)\] was significantly higher than the mean concentration in
canals delivering water to the leaseland fields (0.065 mg/L) and higher
than concentrations reported to be lethal to Daphnia magna (median
lethal concentration of 0.66 mg/L). Dissolved-oxygen concentrations also
were lower, and Daphnia survivability measured during in situ bioassays
was correspondingly lower in the leaseland drains than in water delivery
canals.

In static laboratory bioassays, water samples collected at the primary
monitoring sites cause toxicity in up to 78 percent of Lemna minor
tests, in up to 49 percent of Xenopus laevis tests, in 17 percent and 8
percent of Hyalella azteca and Pimephales promelas tests, respectively,
and 0 percent in Daphnia magna tests. In situ exposure at the sites
caused mortality in more than 83 percent of Pimephales tests and in more
than 41 percent of Daphnia and Hyalella tests. Much of the observed
toxicity appears to have been caused by low dissolved oxygen, high pH,
and ammonia. Although water in the study area was toxic to a variety of
organisms, no statistically significant differences in the degree of
toxicity between sites were observed above or below irrigated
agricultural land in any of the bioassays.

Pesticides were frequently detected in water samples collected at the
monitoring sites during the 1991 and 1992 irrigation seasons. Among the
most frequently detected compounds were the herbicides simazine,
metribuzin, EPTC, and metolachlor and the insecticide terbufos. All the
insecticides detected were at concentrations substantially below acute
toxicity values reported for aquatic organisms.

The herbicide acrolein has been used extensively in the basin to manage
aquatic plant growth in irrigation canals and drains. The concentration
of acrolein was monitored in a canal near Tule Lake after an application
in order to evaluate the potential for the pesticide to be transported
to refuge waters. Although acrolein concentrations were toxic to fish in
the channels adjacent to Tule Lake, very little of the canal water
entered the refuge during the monitoring period.

Organochlorine pesticide concentrations in 25 surficial sediment samples
collected in 1990 were below baseline levels commonly found in soils and
sediment. Seventeen sediment samples were analyzed for chlorophenoxy
acid herbicides and two samples were analyzed for organophosphorus and
carbamate insecticides in 1992. No pesticides were detected in any of
these samples.

Residues of the trace elements selenium, mercury, and arsenic in algae,
invertebrates, fish, and avian eggs revealed no bioaccumulation
problems. Concentrations of organochlorine compounds, especially of
p,p\' DDE, were associated with a mean 11-percent eggshell thinning in
white-faced ibis. However, ibis populations appear to be increasing, and
some eggs of ibis were relatively low in DDE concentration. DDE
concentrations in eggs of western grebes were not as high as in the eggs
of ibis. Concentrations and types of organochlorine compounds detected
in grebe and ibis eggs were highly variable, indicating that the birds
were exposed to these compounds outside the basin.

Fish and invertebrates inhabiting drainwater were representative of
pollution-tolerant species assemblages. The aquatic communities retained
little of their historic ecological structure. Extensive hydrologic
modifications and hyper-eutrophic conditions in Klamath Basin waterways
have degraded the quality of aquatic habitat and altered aquatic
communities.