**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 San Juan River Area,
San Juan County, Northwestern New Mexico, 1990-91

Paul J. Blanchard, U.S. Geological Survey\
Richard R. Roy, U.S. Fish and Wildlife Service\
Thomas F. O\'Brien, U.S. Fish and Wildlife Service

ABSTRACT

Selenium is the trace element of major concern in the San Juan River
area. Concentrations of selenium larger than established standards and
criteria were present in water, bottom sediment, and biota in four areas
on three irrigation projects: the middle and north ponds in Gallegos
Canyon on the Navajo Indian Irrigation Project (NIIP) (two sites), the
Ojo Amarillo Canyon drainage on the NIIP (two sites), a pond receiving
irrigation drainage water on the West Hammond Irrigation Project (one
site). Ground-water return flow from irrigated areas contributes
substantially to surface water at these sites.

Selenium concentrations in nine surface-water samples collected from
these sites exceeded the U.S. Environmental Protection Agency Primary
Drinking Water Standard Maximum. Contaminant Level of 50 µg/L
(micrograms per liter). One additional sample concentration also
exceeded the State of New Mexico standard of 5 µg/L designated for the
protection of fisheries.

Selenium concentrations in five bottom-sediment samples from the middle
pond in Gallegos Canyon, Ojo Amarillo Canyon, and the Hogback Project
ranged from 4.5 to 37 µg/g (micrograms per gram). The geometric mean
concentration of selenium in soils of the Western Untied States is 0.23
µg/g.

Selenium concentrations in biota at six sites in Gallegos and Ojo
Amarillo Canyons, the West Hammond Pond, and the Hogback east drain
ranged from 3.0 to 32.3 µg/g in eight invertebrate samples, 4.22 to 51.3
µg/g in five amphibian samples, and 13.6 to 41.7 µg/g in six fish
samples. Selenium concentrations in 18 of these 19 samples were within
or larger than the 4- to 8-µg/g dry-weight waterfowl food-item
criterion. Six fish samples from these sites also had concentrations
larger than the 12-µg/g whole-body concentration above which
reproductive failure can occur.

The largest median concentrations of selenium in bird liver and kidney
tissue were in six bird samples from the Gallegos Canyon ponds (31.2
µg/g) and four bird samples from Ojo Amarillo Canyon ponds (20.5 µg/g).
Embryo deformities usually occur when the median selenium concentration
in a population is larger than 30 µg/g; however, the potential for
embryo deformities exists when the concentration of selenium is between
10 and 30 µg/g. Due to lack of availability, however, only one embryo
from the Gallegos and Ojo Amarillo Canyons was examined for
teratogenesis. The results of embryo examinations conducted during this
study, therefore, are inadequate to accurately determine conditions
throughout the San Juan River area.

Eleven of 15 plant samples, 6 of 15 invertebrate samples, and 4 of 14
fish samples collected from irrigation project sites had concentrations
of lead larger than the criterion for predator protection of about 1
µg/g dry weight. Four of 13 common carp and flannelmouthed sucker
samples had mercury concentrations larger than the respective 85th
percentile concentrations in these species collected for the National
Contaminant Biomonitoring Program (NCBP).

Concentrations of DDE were larger than laboratory reporting levels in 8
of 10 bottom-sediment samples, 6 of 6 flannelmouthed sucker samples, and
31 of 35 bird samples. In 8 of 16 killdeer samples, concentrations of
DDE were equal to or larger than the 1.0-µg/g wet-weight criterion for
the protection of predators. No concentration in any of the 22
organochlorine compound analyses in the six fish samples was as large as
the respective NCBP geometric mean concentration.