Setmire, J G; Schroeder, R A; Densmore, J N; Goodbred, S J; Audet, D J 



Detailed study of water quality, bottom sediment, and biota associated with 
irrigation drainage in the Salton Sea area, California, 1988-90



Water Resources Investigation Report: 93-4014.



Results of a detailed study by the National Irrigation Water-Quality Program 
(NIWQP), U.S. Department of the Interior, indicate that factors controlling 
contaminant concentrations in subsurface irrigation drainwater in the Imperial 
Valley are soil characteristics, hydrology, and agricultural practices. Higher 
contaminant concentrations commonly were associated with clayey soils, which 
retard the movement of irrigation water and thus increase the degree of 
evaporative concentration. Regression of hydrogen- and oxygen-isotope ratios 
in samples collected from sumps yields a linear drainwater evaporation line 
that extrapolates through the isotopic composition of Colorado River water, 
thus demonstrating that Colorado River water is the sole source of 
subsurface drainwater in the Imperial Valley. Ratios of selenium to chloride 
indicate that selenium present in subsurface drainwater throughout the 
Imperial Valley originates from the Colorado River. The selenium load 
discharged to the Salton Sea from the Alamo River, the largest contributor, is 
about 6.5 tons/yr. Biological sampling and analysis showed that drainwater 
contaminants, including selenium, boron, and DDE, are accumulating in 
tissues of migratory and resident birds that use food sources in the 
Imperial Valley and the Salton Sea. Selenium concentration in fish-eating 
birds, shorebirds, and the endangered Yuma clapper rail were at levels that 
could affect reproduction. Boron concentrations in migratory waterfowl and 
resident shorebirds were at levels that potentially could cause reduced growth 
in young. As a result of DDE contamination of food sources, waterfowl and 
fish-eating birds in the Imperial Valley may be experiencing reproductive 
impairment.



water pollution sources; fate of pollutants; pesticides; irrigation 
drainage; selenium; bioaccumulation; wildlife management; USA, California, 
Salton Sea; bottom sediments; subsurface drainage; nonpoint pollution; water 
quality; toxicity; wildlife; irrigation; drainage