Water Contamination Problems at Kesterson Reservoir
In 1983 the Fish and Wildlife Service noticed that something had gone terribly wrong at the Kesterson Reservoir in central California's San Joaquin Valley: some of Kesterson's newly hatched waterfowl had crippling deformities. Beaks were grotesquely shaped, wings were missing, legs were twisted, and skulls were unformed; many birds died soon after hatching. The reservoir--ironically, part of the Kesterson National Wildlife Refuge--had become hostile to its inhabitants, and the name "Kesterson" soon became synonymous with environmental disaster.
The cause of this ruin was eventually diagnosed as selenium, a naturally occurring nonmetallic trace element. Selenium was being leached from the soil underlying some portions of the Westlands Water District by agricultural irrigation water. Subsurface drains collected this water and then carried it to the reservoir through the San Luis Drain. Once in Kesterson, the mineral became concentrated in vegetation and small animal life, and the concentrations increased dramatically as selenium moved up the food chain. Selenium in very small amounts is regarded as beneficial to humans, but at higher levels it almost certainly is dangerous. For bird life, the verdict is clear: high concentrations of selenium are fatal.____________________