Sinking farmland snags San Joaquin River project

The Fresno BeeDecember 8, 2012 

The San Joaquin River restoration has hit a strange snag -- a vast area of swiftly sinking farmland. It means the much-heralded return of salmon runs to the state's second-longest river will wait a little longer.

Over the past two years, irrigation pumping near the river has caused a two-foot dip in the landscape across many square miles on the Valley's west side, federal engineers say.

Now, just months from the start of major construction in the restoration, the engineers must rethink the $25 million replacement of Sack Dam, which will have special features for salmon passage.

If the land keeps sinking, a new dam could be overrun and farmers would lose irrigation water. Also, salmon might die if they swim over the top of a screen that will be installed to keep them out of a large irrigation canal, called Arroyo Canal.

Options are being considered, including raising the height of the dam and the screen, said Alicia Forsythe, restoration program manager for the U.S. Bureau of Reclamation. She said it might be necessary for pumps to be installed to get river water into Arroyo Canal.

This is the latest and perhaps most unexpected hurdle for one of the nation's most complex river restorations, which has a price tag of nearly $900 million.

The program was scheduled this month to begin salmon migration from places near Fresno all the way to the Pacific Ocean. But there isn't a clear path around Sack Dam and the Mendota Pool for fish to move up and down the river yet.

Instead, biologists have been capturing adult salmon and hauling them to the river near Fresno for spawning -- part of the continuing experiments. Until Sack Dam and other projects are built, the full restoration of salmon won't happen.

Sack Dam, which captures water for 45,000 farmland acres, is in the most troubled stretch for the restoration. The stretch is about 60 river miles along the Valley's west side where the river dried up in the early 1950s after Friant Dam was built.

A new Sack Dam will be built with both a fish ladder and a system to raise and lower the dam so salmon can pass through. A new screen on Arroyo Canal will prevent salmon from accidentally straying into the irrigation system for farmers west of the San Joaquin.

A sinking landscape is too widespread and subtle to notice easily, experts say. The problem at the river was discovered this year when irrigation districts noticed they were having trouble getting as much irrigation water as they usually capture.

Federal engineering reports confirmed land subsidence, which lowers canals and reduces the amount of water that can be carried.

Farmers on the east side of the river in Madera County have been pumping more water from deep underground to support crop expansions and changes in the past several years. The farmers, who reportedly did not realize there was a problem, rely on groundwater.

Area water districts are working with the farmers on a plan to limit the deep-water pumping. It's a huge issue, says Chase Hurley, general manager of San Luis Canal Co., which relies on Sack Dam, the delivery canal and the river.

"That's my only turnout for water," Hurley said. "We're encouraged that everybody is working together on this."

The deep-water pumping goes down 300 to 800 feet, below ancient layers of clay soil. When the water is drained from these areas, the clay layers collapse, Hurley said.

He and another leader, Chris White, general manager of Central California Irrigation District, say it's important to replenish underground water at shallow depths so the deep-well pumping stops. They propose using excess water in wet years to form recharge ponds.

"The idea is to help them get water from shallower wells," White said. "You won't get this kind of subsidence if the pumping takes place above the clay at shallower depths."

The reporter can be reached at (559) 441-6316, or @markgrossi on Twitter.

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