Writing on the wall for prime farmland. Years of irrigation have taken toll on San Joaquin Valley.

Carolyn Lochhead. March 24, 2014. Writing on the wall for prime farmland. Years of irrigation have taken toll on San Joaquin Valley. San Francisco Chronicle.

Decades of irrigation have leached salts and toxic minerals from the soil [in the San Joaquin valley] that have nowhere to go, threatening crops and wildlife.

Aquifers are being drained at an alarming pace.

More than 95% of the area’s native habitat has been destroyed by cultivation or urban expansion, leaving more endangered bird, mammal and other species in the southern San Joaquin than anywhere in the continental U.S.

Federal studies long ago concluded that the only sensible solution is to retire hundreds of thousands of acres of farmland.  The 600,000-acre Westlands Water District has already removed tens of thousands of acres from irrigation.   Many experts said if farmers don’t retire the land, nature eventually will do it for them.

More than a decade ago, Jack Mitchell, now 74, sold 3,000 acres of his irrigated land to federal officials trying to find out whether imperiled farmland could be restored. Mitchell’s farm was on the site of the old Tulare Lake, once the largest freshwater lake west of the Mississippi, covering 800 square miles and yielding 3-foot trout. It went dry in the early 20th century as farmers began diverting water.  In 2006, the U.S. Fish and Wildlife Service said that despite hundreds of millions of federal dollars spent over two decades, no technological solution had been found to dispose of drain water. Enormous amounts of salt and selenium – toxic to birds, other wildlife and humans at high concentrations – continue to accumulate each year.

The San Joaquin Valley is an ancient seabed arid enough to be classified as desert but irrigated by a huge complex of dams and canals. Large swaths of it have serious drainage problems, including more than 1.75 million acres of farmland, according to a 2005 federal report.

Much of the problem land lies on the valley’s west side, represented primarily by Westlands. More than half its acreage has been classified as drainage-impaired.

The Fish and Wildlife Service concluded that the best solution is to “remove the fundamental underlying source of the problem” by retiring 379,000 acres of land from irrigation.

In 2008, the U.S. Geological Survey warned that within 50 years, 20 million tons of contaminated salt will have to be disposed of. The agency said experimental technologies are “unprecedented and untested at the scale needed” and that the “potential release of selenium-contaminated drainage is massive.” The agency concluded that the best solution would be to retire 300,000 acres in the western San Joaquin Valley.

In some areas of the valley, salt has crystallized on the surface, covering fields with what is known as “California snow,” rendering the ground useless not just for crops but also for any vegetation at all.

Retiring lands before they reach that point “has just got to be the highest priority for California,” said Tom Stokely, a water policy analyst for California Water Impact Network, an environmental group. “We don’t have the water to be irrigating these poisoned lands. We’re having a hard enough time keeping the good lands in production.”

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