| Abstract: | Selenium in tile drain water from parts of the western San Joaquin Valley, California, has adversely affected fish and waterfowl where drain water was impounded. Soils in these drained areas were derived from Coast Range marine sedimentary formations, were naturally saline and probably contained abundant soluble selenium. Decades of irrigation have redistributed the most soluble forms of selenium from the soil into groundwater and have caused the water table to rise 1 to 4 ft/year. Selenium in shallow groundwater has been further concentrated because of evapotranspiration. The rising water table has caused a large area of farmland to require artificial drainage of groundwater that contains high concentrations of selenium. The present areal distribution of selenium in shallow groundwater reflects the natural distribution of saline soils. The depth distribution of selenium in groundwater reflects the history of irrigation. The highest concentrations of selenium in groundwater (50 to more than 1,000 micrograms/L) are in a zone of variable thickness located between 20 and 150 ft below the water table. The toxic water in this zone was recharged during the first few decades of irrigation. The large volume of high selenium groundwater makes it desirable to leave this water where it is, rather than bring it to the land surface or allow it to move into parts of the aquifer that may be used for water supply. Selenium concentrations in the San Joaquin River depend on the magnitude of the selenium load from drain water and dilution by water with low concentrations of selenium from all other sources of streamflow. The San Joaquin Valley is a regional-scale example of how manipulation of the hydrologic system can cause water quality problems if naturally occurring toxic substances are mobilized. (USGS) |
| Genre: | USGS Numbered Series |
| ProdID: | 27312 |
| Citation Author: | Gilliom, R. J. |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | x, 129 p. :ill., maps ;28 cm. |
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| Citation Publisher: | U.S. Geological Survey, |
| Citation Series: | Water-Resources Investigations Report |
| Citation Series Code: | WRI |
| Citation Series Number: | 88-4186 |
| Citation Search Results Text: | Preliminary assessment of sources, distribution, and mobility of selenium in the San Joaquin Valley, California; 1989; WRI; 88-4186; Gilliom, R. J. |
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| Citation Year: | 1989 |
| Type: | citation/reference |
| Text: | Preliminary assessment of sources, distribution, and mobility of selenium in the San Joaquin Valley, California; 1989; WRI; 88-4186; Gilliom, R. J. |
| URL (THUMBNAIL): | http://pubs.usgs.gov/wri/1988/4186/report-thumb.jpg |
| URL (DOCUMENT): | http://pubs.usgs.gov/wri/1988/4186/report.pdf |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
| Publisher: | U.S. Geological Survey, |
