Linking Selenium Sources to Ecosystems: Irrigation

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Adverse effects of selenium (Se) on fish and waterfowl in wetlands receiving agricultural drainage occurred in the 1980s in the San Joaquin Valley of California. The identified mechanisms of Se enrichment helped resolve Se toxicity problems associated with irrigated agriculture in the arid West. Bioaccumulation of Se in ancient marine sediments is postulated as a primary pathway in source rocks.

The Kesterson Effect - from Rock to Duck

Graph showing selenium concentration vs. water flux.

Figure 1.  Selenium concentration vs. water flux.

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.

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.

Black-necked stilt embryos from nests at Kesterson Reservoir showing deformities.

Figure 2.  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).

Diagram showing the Kesterson Effect in Kesterson National Wildlife Refuge, San Joaquin Valley, CA.

Figure 3.  Selenium contamination of the Kesterson National Wildlife Refuge is traced through irrigation drainage to the source bedrock of the California Coast Ranges. This biogeochemical pathway of selenium is defined here as the "Kesterson effect." At the refuge ponds, this effect culminated in 1983 in a 64% rate of deformity and death of embryos and hatchlings of wild aquatic birds. Selenium, as selenate, was ultimately found weathered with sulfur from marine sources in soluble sodium and magnesium sulfate salts, which are concentrated by evaporation on farmland soils. The Se, mobilized by irrigation drainage, is bioaccumulated to toxic levels in refuge wetland ponds that are located mainly in hydrologically closed basins and thus act as concentrating disposal points. The depositional environment of the ponds may be similar to that of the nutrient-rich continental shelf edge and slope in which Cretaceous, Eocene, and Miocene sediments found to be seleniferous in the California Coast Ranges were deposited. Bioaccumulation may be, therefore, a primary mechanism of selenium enrichment in ancient sediments in addition to that of the formerly suggested Cretaceous volcanic pathway.


Western United States

Map showing location of National Irrigation Water Quality Program study areas.

Figure 4.  Location of several National Irrigation Water Quality Program study areas in the Western United States selected because of potential irrigation-drainage water-quality problems. Also shown are data-collection sites within study areas.  Modified from Seiler et. al., 2003.

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.

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.

Photo of Sibling stilt embryos with deformities.

Figure 5.  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)

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



Presser, T. S., and Ohlendorf, H. M., 1987, Biogeochemical cycling of selenium in the San Joaquin Valley, California: Environmental Management, v. 11, p. 805-821.

Skorupa, J.P. and Ohlendorf, H.M, 1991, Contaminants in drainage water and avian risk thresholds, in A. Dinar and D. Zilberman, eds., The Economics and Management of Water and Drainage in Agriculture, Kluwer Academic Publishers, Boston Massachusetts, p. 345-368.

Presser, T.S., 1994, The Kesterson Effect: Environmental Management, v. 18, no. 3, p. 437-454.

Presser, T.S., Sylvester, M.A., and Low, W.H., 1994, Bioaccumulation of selenium from natural geologic sources in the Western States and its potential consequences: Environmental Management, v. 18, no. 3, p. 423-436.

Skorupa, J.P., 1998, Selenium poisoning of fish and wildlife in nature: lessons from twelve real-world examples, in Frankenberger, W.T., Jr., and Engberg, R.A., eds., Environmental Chemistry of Selenium: Marcel Dekker Inc., New York, p. 315-354.

Presser, T.S. and Piper, D.Z., 1998, Mass balance approach to selenium cycling through the San Joaquin Valley, sources to river to bay, in Frankenberger, W.T., Jr., and Engberg, R.A., eds., Environmental Chemistry of Selenium: Marcel Dekker Inc., New York., p. 153-182.

Seiler, R.L., Skorupa, J.P., Naftz, D.L. and Nolan, B.T., 2003, Irrigation-induced contamination of water, sediment, and biota in the western United States-synthesis of data from the National Irrigation Water Quality Program: U. S. Geological Survey Professional Paper 1655, 123 p.

Presser, T.S., 2004, Agriculture in the Western United States.