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

Monitoring of Inorganic Contaminants Associated with Irrigation Drainage
in Stillwater National Wildlife Refuge and Carson Lake, West-Central
Nevada, 1994-96

Tuttle, P.L.; Hoffman, R.J.; Wiemeyer, S.N.; Miesner, J.F.

ABSTRACT

In 1994, the U.S. Geological Survey and the US Fish and Wildlife Service
initiated a 3-year drain-water and wetland-monitoring program in
Lahontan Valley, Nevada, as part of the National Irrigation Water
Quality Program of the U.S. Department of the Interior. The purpose of
the monitoring was to (1) develop a long-term hydrologic and biologic
data base, (2) provide a baseline to evaluate the effects of Federal
activities on water quality, wetland quality, and biota in the area, and
(3) identify progress toward remediation of contaminant concerns in
Lahontan Valley wetlands. Specific data collected included drain-water
quantity and quality; trace-element concentrations in water, sediment,
and biological samples from wetlands; aquatic-invertebrate and fish
diversity and relative abundance in wetlands; fish condition; bird use
of wetlands; acreage of major wetland habitat types; and toxicity of
water to test organisms.

Consistent with previous National Irrigation Water Quality Program
investigations, some inorganic contaminants exceeded applicable
beneficial-use criteria or levels of biological concern during 1994-96.
Water flowing in some agricultural drains into the wetlands contained
concentrations of dissolved boron and molybdenum and total mercury that
frequently exceeded applicable beneficial-use criteria. Loads of
dissolved solids, boron, and mercury were greatest during the irrigation
season coincident with increased flow. In the wetlands of Stillwater
National Wildlife Refuge, aluminum, arsenic, boron, lead, mercury,
molybdenum, and zinc in unfiltered water samples exceeded State and (or)
Federal criteria for the protection of designated beneficial uses of
water; arsenic and mercury in sediment exceeded potentially toxic
levels; and aluminum, boron, mercury, and zinc in biological tissues
exceeded levels associated with lethal or sublethal effects on fish and
wildlife. Concentrations of selenium generally were below levels of
biological concern in all sample media.

Invertebrate-community species composition and community structure
varied among wetlands and among years. Dominant invertebrate taxa were
classified as moderately to highly tolerant of pollutants.
Concentrations of arsenic, boron, and molybdenum in unfiltered water and
arsenic, mercury, and possible selenium in sediment collected from
wetlands correlated with effects on aquatic invertebrate communities.
Fish species assemblages, which consisted of one native species and four
introduced species, also varied among years and among wetlands. Fish
species present were classified as moderately tolerant to tolerant of
pollutants. Measures of fish condition were inconsistent among species
and among wetlands. The presence of larval fish suggested successful
fish reproduction in Lahontan Valley wetlands. Bird use of wetlands also
varied among wetlands and among years.

Wetland-habitat acreage increased over the course of this investigation.
The increase was attributed to regional climatic patterns and the
increase of water flow to wetlands during the 1994-96 study.
Corresponding to increased water inflow, the areal extent of open water
and associated emergent-vegetation habitats also increased.

Specific conductance, a surrogate measure of dissolved-solids
concentration, appeared to be a useful variable to monitor the levels of
salinity and certain potentially toxic trace elements in drains and
wetlands of Lahontan Valley.