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Introduction
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IRRIGATION
The
Kesterson Effect - from Rock to Duck |
The
most well known case of Se poisoning occurred in 1983 at Kesterson
National Wildlife Refuge in the San Joaquin Valley, California.
Widespread fish mortality and deformities in ducks, grebes, coots,
and shorebirds occurred in wetlands fed by agricultural irrigation
drainage. The types of deformities most frequently observed were
defects of eyes, feet or legs, beaks, brain, and abdomen. Further
south in Tulare Basin, a higher level of tetratogenicity (56.7%)
occurred in shorebirds inhabiting ponds where accelerated evaporation
was taking place. Drainage canals remain posted with human health
advisories against consumption of fish.
 
Photos Courtesy of U.S. Fish and Wildlife Service
Black-necked
stilt embryos from nests at Kesterson Reservoir: (S-9) Eyes missing,
severe exencephaly through orbits, lower beak curled, upper parts
of legs shortened and twisted, and only one toe on each foot.
(S-35) Eyes missing, encephalocele, upper beak elongated and eroded
at nostrils, lower beak missing, legs missing, and only one (small)
wing. (S-302) Eyes missing, upper beak curved, lower beck shortened
and tip of lower beak “hooked”, hydrocephaly, edema
in throat, legs twisted, and feet shortened with only one toe
on each foot. (S-313) Normal.
(Also see Press and Ohlendorf, 1987, Environmental
Management, 11 (6):805-821).
Click
on image to enlarge. |
The
geohydrologic balance of Se ultimately determines the degree of
contamination build-up in the San Joaquin Valley. The primary geologic
inventory of Se in the Coast Ranges is the source of influx. Drainage,
whether natural or accelerated by engineering, is the source of
efflux. Se concentration in agricultural drainage is not diluted
when flow increases, except in extreme precipitation events, (e.g.,
an El Nino year). Rather, increasing input of water results in increased
Se concentrations and loads, indicating a large internal reservoir
of Se that currently influences water quality.
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Western
United States
The
U.S. Department of the Interior manages approximately 200 wildlife areas
that receive water from more than 400 USDOI water projects in 17 western
states. With Kesterson National Wildlife Refuge as a prototype, reconnaissance
areas for study of Se contamination by the USDOI were generally selected
based on six factors being present:
1.
A basin of saline marine sedimentary origin that includes soils derived
from Cretaceous deposits (Note: See mining for updated source rock discussion);
2. Oxidized, alkaline soils
that promote the formation of selenate, the mobile form of Se;
3. An arid to semiarid climate
with evaporation much greater than precipitation, leading to salination
of soils;
4. Irrigated agriculture served
by USDOI-supported irrigation-drainage facilities to leach salts;
5. Saline groundwater aquifers
resulting mainly from alluvial clay layers that impede downward movement
of irrigation water and cause water logging of the crop root zone;
6. Drainage by natural gradient
or buried tile drain networks to USDOI managed migratory-bird refuges,
wetland areas, or other areas in receipt of USDOI waters.
Modified from Seiler et. al., 2003. (http://pubs.usgs.gov/pp/pp1655) |
Names
and locations of the 26 areas studied by the USDOI are shown in
the accompanying map. The illustrated sites encompass the areas
historically shown to support seleniferous open-range forage plants
associated with the Pierre and Niobrara Formations (or their equivalents).
Livestock deaths attributed to Se poisoning from these plants occurred
in Wyoming, Nebraska, and South Dakota in the 1930 and 1940s, leading
to land being withdrawn from use by livestock. Following this "open
range era" of Se contamination, the "aquatic era"
of Se contamination was marked by irrigation-drainage Se sources.
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Those
study areas where contaminated agricultural drainage caused harmful
accumulation of Se are the following:
1. Tulare
Basin, San Joaquin Valley, California
2. Salton Sea, California
3. Middle Green River
Basin, Utah
4. Stillwater Management
Area, Nevada
5. Kendrick Reclamation
Project, Wyoming
6. Gunnison-Grand Valley
Project, Colorado
7. San Juan River Area,
New Mexico
8. Sun River Area, Montana
9. Riverton Reclamation
Project, Wyoming
10. Belle Fourche Reclamation,
South Dakota
11. Dolores-Ute Mountain
Area, Colorado
12. Lower Colorado River
Valley, California-Arizona
13. Middle Arkansas Basin,
Colorado-Kansas
14. Pine River Area, Colorado |
Sibling
stilt embryos collected from a single nest on the same day from
a Tulare Basin evaporation pond in 2001. The overtly teratogenic
embryo on the left, exhibiting stunted growth, no eyes, deformed
bones (in right foot) contained 72 ppm Se (dw, whole egg), while
the overtly normal sibling, on the right, contained 16 ppm Se. (photo
courtesy of USFWS) |
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