Oil and water | An uneasy mix in farm fields of the Central Valley

Scott Smith, chief scientist at Water Defense, deploys foam sponges to absorb test water from a canal operated by the Cawelo Water District near Bakersfield. The canal moves oil-produced water mixed with fresh water for use by Kern County farms. (Brian van der Brug / Los Angeles Times)

April 21, 2015 11:48 AM PT

Chevron sells millions gallons of treated oil field wastewater each day to Kern County growers, who use it on some 45,000 acres of thirsty crops.

Oil-produced water in a polishing pond operated by the Cawelo Water District near Bakersfield. (Brian van der Brug / Los Angeles Times)

Water flows into a holding pond at a Kern County vineyard near Bakersfield. Water in the reservoir was tested last summer by Scott Smith, chief scientist at Water Defense. (Brian van der Brug / Los Angeles Times)

Scott Smith, chief scientist at Water Defense, right, and assistant Skye Wallin retrieve foam sponges which absorbed canal water for testing near Bakersfield. The canal moves oil-produced water mixed with fresh water for use by Kern County agriculture. (Brian van der Brug / Los Angeles Times)

A foam sponge to absorb test water from a canal operated by the Cawelo Water District near Bakersfield. The canal moves oil-produced water mixed with fresh water for use by Kern County farms. (Brian van der Brug / Los Angeles Times)

Scott Smith, chief scientist at Water Defense, left, and assistant Skye Wallin retrieve foam sponges which were deployed to absorb test water from a canal in the Cawelo Water District near Bakersfield. (Brian van der Brug / Los Angeles Times)