UC Project Seeks Reuse of Farms’ Wastewater

While government agencies at all levels battle about how to eliminate contamination by toxic farmland wastewater, scientists from the University of California are looking for a way to reuse the mineral- and salt-laden liquid.

The 10-year experiment in the San Joaquin Valley is headed by Dennis E. Rolston, professor of land, air and water resources at the University of California, Davis.

“We’ve known for years that the land in the San Joaquin Valley will contaminate irrigation water, making it unusable,” Rolston said. “What we hope to do is find a way to dilute and recycle the agricultural drainage water to slow the buildup of highly saline water tables in the valley and decrease the amount of drainage water which must be removed to evaporation ponds.”

Creating an Uproar

The water that is shipped to evaporation ponds, especially those in the Kesterson National Wildlife Refuge near Los Banos in Merced County, is causing the latest environmental uproar in the valley.

Scientists determined that trace minerals in the drainage water, especially selenium, are causing deaths and deformities among birds in and around the refuge. They also fear that selenium and other concentrations of toxic minerals are working their way through the soil at the refuge and into the ground-water table.

State water officials have ordered the federal Bureau of Reclamation to find a way to clean up the refuge or close it to farmland waste-water drainage.

“If we could find a way growers could reuse drainage water, they could decrease the volume of water requiring disposal,” Rolston said. “They would have to import less water for irrigation and pump less drainage water to evaporation ponds.”

10-Year Experiment

Rolston’s team of scientists and researchers has built a full-scale farm field in the Tulare Lake Drainage District near Corcoran in Kings County for the 10-year experiment to find out how diluted drainage water affects crops.

The experimental field is now in its second season of cotton cultivation, using drainage water diluted with fresh water in six different amounts for irrigation.

“The major objective is to determine the response and yield of crops when exposed to different salinity levels over a typical cropping rotation,” Rolston said.

He said researchers also will study how various salinity levels in the irrigation water affect the soil and how the effect correlates with crop productivity.

Rolston said that during the first growing season, virtually no change was noted in crop vigor or productivity with any of the six salinity-level irrigation waters used on the experimental farm.

“But as salinity builds up during the next few years, I think data will indicate just how much the drainage water will have to be diluted with fresh water to make it usable,” he said.