Course: Science Subtest I
Lesson: Earth's Resources
Topic: California's Fresh Water      Page 37 of 39  

In California, the buildup of some specific salts came to the public’s attention in the early 1980s, when migratory waterfowl and fish in Kesterson Reservoir in the San Joaquin Valley began to sicken, die, or disappear. Farmers were also reporting the deformity or death of livestock. An investigation by state and federal researchers revealed that agricultural drainage water directed into the reservoir was very high in selenium salts, which occur naturally in the soil on the western side of the valley. Although selenium in low doses is vital to life, at sufficiently high levels, selenium is toxic to wildlife and humans.

Remediation of the Kesterson Reservoir area began immediately, and environmental agencies and academic researchers began studying the newly named Kesterson effect to see how it can be avoided. The U.S. Bureau of Reclamation is studying options to address drainage issues in the San Joaquin Valley and keep selenium out of the food chain. State officials now see the problem as one of preserving the sustainability of agriculture in the Central Valley; the California Health and Safety Code declares that “the buildup of salt and selenium in agricultural soil is an unsustainable practice that degrades soil, harms an irreplaceable natural resource, reduces crop yields and farm income, and poses threats to wildlife.”