Working Around Salty Residue in Nation’s Breadbasket
Salt buildup in America's most productive farming area could idle thousands of acres. But there are, ahem, solutions …
While California’s farmers grapple with a record-setting drought, an ancient enemy lurks beneath a layer of topsoil in an area that’s been dubbed “the most productive unnatural environment on Earth.”
Just below the surface of 2.5 million acres of California’s most fertile and productive farmlands lie pockets of residual brine. Perched, shallow groundwater infused with boron, sodium sulfate, selenium and other minerals common to seawater points to the submarine origins of the state’s fertile Central Valley, which by dollar value produces as much as a quarter of the nation’s agricultural value.
Jose Faria, manager of agricultural drainage for California’s Department of Water Resources, said the region’s farmers have customarily met the challenge of saline, perched groundwater through specialized irrigation practices, designed to wash salts away before seeding, to keep them from infiltrating the root zone and endangering crops.
That, he said, creates highly saline runoff that presents a thorny disposal problem of its own.
A Job for a Plumber
The U.S. Bureau of Reclamation, in an effort to solve the problem, in the 1960s proposed taking salt- and mineral-laden runoff from farm to sea over a 300-mile drainage network. However, as the project started, strange things began happening in areas receiving the farm drainage.
Public outcry arose when nightmarish deformities were observed in birds nesting near Kesterson Reservoir, a lake that had served as a temporary storage basin for farm runoff until the drain project was completed. Investigators traced the deformities to selenium — a nutrient in tiny doses but toxic in larger ones — that washed from farms and concentrated in the lake.
In 1983, after the completion of only two miles of the proposed drain, the scheme was abandoned. The lake’s waters were deemed hazardous, the surrounding park was shut down and birds were discouraged from roosting in the area.
(Furthermore, as a result of Kesterson, the U.S. Department of the Interior started looking at other sites in the federally irrigated West and, in 1985, founded the National Irrigation Water Quality Program to identify and possibly fix similar problem sites. Funding for the program, however, essentially dried up in 2005, with remediation having occurred at only two places, Utah’s Middle Green River and Colorado’s Gunnison/Grand Valley.)
After that, farming became more difficult as California regulators, responding to environmental concerns, clamped down on irrigation discharges. According to Baryohay Davidoff, chief of agricultural water management for the California Department of Water Resources, San Joaquin Valley growers have since been required to virtually “eliminate all discharges of agricultural drainage in the areas affected by selenium.”
Farmers along the western San Joaquin Valley were left to watch helplessly as salts and minerals accumulated on their fields, with no better prospect than an appeal for government compensation, as they retired ever-widening swaths of formerly productive farmlands.
But in the current era of tightening budgets and looming food crises, Faria said the land retirement solution has become “unsustainable.” And equally important, in order to prevent encroaching desertification — similar to what, he says, in ancient times “happened in Mesopotamia” — the drainage issue will have to be addressed, and soon.
In the few short decades since Kesterson, Faria said growers in the Westlands Water District alone have been forced to retire 100,000 acres of farmland, as a consequence of salt damage and selenium contamination — one-sixth of the massive district’s arable acreage.
The economic consequences, he said, are staggering, with lost farm productivity estimated at $200 million per year in the district — not to mention the cost of compensation paid to farmers and the loss of opportunities for the region’s farmworkers and their families.
Taking the minerals out of the drainage is wildly expensive. According to Heather Cooley of the nonpartisan think tank Pacific Institute, desalination can cost up to thousands of dollars per acre-foot, far beyond the reach of agricultural water users. Plus, Faria noted, the most-promising drainage-water desalination systems are still in various stages of development, not yet ready for widespread application.
Furthermore, constructing drainage basins to retain briny water on farm property, the traditional solution to saline runoff, requires taking valuable acreage out of production — something small-scale farmers are loath to do.
Faria said official estimates of the cost of providing a comprehensive drainage system for the affected croplands hover around $2.7 billion. And, he said, none of the agencies involved “have that kind of money lying around.”
However, Faria believes one readily available solution — a practice called Integrated on-Farm Drainage Management — can preserve farmland while protecting the environment. And farmers adopting it out of necessity, he said, are realizing its virtues.
IFDM rests on two pillars: source control and drainage reuse.
Source control simply means limiting the amount of water used in irrigation (which obviously limits drainage). Davidoff said the state provides irrigation districts with several resources to help farmers accomplish this, including a network of 260 weather stations, as well as irrigation specialists equipped with mobile laboratories to test soil characteristics and advise farmers on improved irrigation practices.
Upgrading from traditional flood and furrow watering to sprinkler or drip irrigation, recommendations endorsed by Faria, allows growers to target their watering can where it’s needed most.
But it’s IFDM’s recommendations for drainage reuse that get agriculturalists’ creative juices flowing.
For example, in a typical IFDM scenario, Faria said, high-value water-intensive crops, such as iceberg lettuce or cantaloupes, are grown in the center of the fields; water applied to these crops is allowed to drain into a surrounding buffer zone of salt-tolerant crops, such as alfalfa. Each successive ring of vegetation takes up its share of water, leaving behind an ever-more-concentrated saline effluent. Along the perimeter of the fields, practitioners grow a ring of even-more-salt-tolerant trees, such as pistachios, or halophytes, such as salt grass, which, as its name implies, thrives in saline conditions.
Finally, any water not taken up by the plants themselves is channeled to a solar evaporator, which captures the dry salt residue.
IFDM “saved the farm,” said Michael Andrews, whose AndrewsAg Inc. farms 2,000 acres in the Bakersfield area.
“We had a mini Kesterson right here on the farm,” he said. In an effort to comply with mandated drainage restrictions, Andrews said, between 1995 and 1998, farm runoff had been collected and stored in a 100-acre, traditional farm drainage basin on the property. Over a period of just a few years, the pond had accumulated near-toxic levels of selenium.
“We even had the deformed birds,” Andrews added.
A low-value cotton crop was the only thing, he said, that could be grown in the saline soil. And the combination of marginal productivity and regulatory liability had driven the appraised value of the property to zero.
According to Andrews, after learning about IFDM at a conference several years ago, he “shut down the ranch for a year, let the basin dry out, converted the plumbing and reconfigured the drainage system” for reuse.
Now, with less than 10 percent of his acreage dedicated to salt-tolerant crops and halophytes, Andrews said, he grows “12 different items,” Including highly marketable fruits and vegetables. “The salt-tolerant crops and halophytes are up-taking almost all of the drainage.”
As a bonus, he said, the salt grasses volatilize selenium as they grow, removing the element from the drainage and rendering it harmless.
He also said switching to IFDM has reduced overall drainage volumes on the farm by 90 percent, and selenium levels by 80 percent, well below the toxicity threshold. In addition to a new harvest of alfalfa and salt grass, Andrews has entertained inquiries concerning an unusual farm crop — the salt crystallizing in the ranch’s solar evaporators.
Andrews offers advice to farmers considering making the transition to IFDM, through his Web site.
While he conceded “it’s not easy. It takes capital, regulatory cooperation and patience,” the approach transformed “marginal farmland into exceptional farmland. … We converted an environmental liability into an asset valued at $10 million. Converting to IFDM is well worth it.”
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