How did ag drainage result in an environmental disaster?

By Raquel UyMarch 1, 2013 

The San Joaquin Valley is known as California's leading agricultural producer, and maintaining it is no easy task.

Even from the time cattlemen Henry Miller and Charles Lux began their development in this area in the late 19th century, agricultural drainage was a problem. When cases of two-headed coots and duck embryos with organs outside their bodies were discovered in the 1980s at Kesterson Reservoir about 20 miles north of Los Banos, federal wildlife officials were alarmed.

"We can classify this as an environmental disaster," said Gary Zahm, a one-time manager of the Kesterson National Wildlife Refuge and reservoir.

Farmers saw it as an economic disaster threatening their livelihood. Many interim fixes were tried, but the problem persists today, but to a lesser degree.

The culprit was agricultural drainage water laced with selenium, a heavy element that occurs naturally in the soil. It is essential to life in small quantities; in larger quantities, deformities or other problems may occur. The water was stored in Kesterson Reservoir until the problem was discovered and the reservoir drained.

Historically, many natural salts remained in the valley soil after being submerged in ocean water many years ago. The Westside does not receive much rain, so water from the east had to be transported in via canals for farmers to use, and this irrigated water picked up a lot of salt along the way. To add to the increasing salinity problem, the layers of clay beneath the soil prevented water from penetrating and draining properly.

Around the 1870s, Henry Miller began building canals to ensure proper irrigation and to control the accumulation of salts. Many years later, additional canals were built to pump water from Northern California through the Sacramento-San Joaquin Delta and Delta-Mendota Canal to the northern San Joaquin Valley.

With that, the U.S. Bureau of Reclamation began the construction of the San Luis Drain in 1968. Its goal was to carry irrigation drainage water from the valley and dispose of it into the delta. Many in the delta opposed the construction of the drain because they were apprehensive about the quality of water they would be receiving. In 1975, funding limitations caused the construction of the San Luis Drain to stop at Kesterson Reservoir.

Farmers expected water and salt problems as the drainage systems were being built. However, they didn't anticipate that the problem would be selenium. They thought it was just a salinity issue until they started discovering deformities in the wildlife that came in contact with the waters at Kesterson Reservoir.

When the drain ended at Kesterson, the water was left to evaporate and the problem intensified. After examining water samples, biologists and wildlife officials discovered the high concentration of selenium in the stagnant water.

Many feared that the animals they hunted were contaminated or that they may have eaten contaminated plants.

"Discovery of the selenium has really changed how farmers in the valley manage the irrigation of the croplands," Zahm said.

The San Joaquin Valley Drainage Program was established in 1984 to examine and solve further drainage problems. Unfortunately, this joint federal and state effort could not find efficient solutions, and the reservoir was eventually ordered to be drained and closed in 1986. However, the San Luis Drain was partially reopened in the 1990s as part of the Grassland Project, which was another attempt to take away the drainage water contaminated with selenium.

Selenium levels are not as high now. Dennis Falaschi, who manages the Panoche Water District and the Pacheco Water District, said selenium contamination remains an ongoing problem but progress is being made. More advanced equipment for water treatment is being used. There is a method called "reverse osmosis" that cleans half the water by making the water flow through a membrane trapping the harmful elements, including selenium; the other half contains the high concentration of those elements. He said the best way to improve agricultural drainage is to keep the water flowing.

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