Central Valley’s Sinking Land Threatens Vital Canals

The Russell Avenue bridge over the Delta-Mendota Canal in Firebaugh had subsided so much in July, 2015 that there was almost no space between the bottom of the bridge and the canal water.

The Russell Avenue bridge over the Delta-Mendota Canal in Firebaugh had subsided so much in July, 2015 that there was almost no space between the bottom of the bridge and the canal water. (Department of Water Resources)

FRESNO — Land in the Central Valley is sinking so much from over-pumping of groundwater during the drought that officials said Thursday they will press for new laws to limit drilling.

The sinking threatens to curtail as much as one-fifth of water deliveries through the vital California Aqueduct to San Joaquin Valley farms and millions of Southern California residents, state water managers said.

They cited NASA satellite images that show the land dropping in places by as much as a foot a year.

In 2014, lawmakers approved legislation ending a Gold Rush-era policy that generally let property owners pump as much water as they wanted. However, the law gave local agencies until 2040 to fully implement groundwater plans.

“Considering the damage we’ve seen now, we can’t wait until 2040,” said Jeanine Jones, a California Department of Water Resources manager.

The California Aqueduct stretches 444 miles from the San Joaquin-Sacramento River Delta east of San Francisco to Southern California, providing water to 25 million people and nearly a million acres of farmland.

Sections of the concrete canal have dropped more than two feet in some places, officials say.

The sinking Central Valley threatens to curtail as much as one-fifth of water deliveries through the vital California Aqueduct to San Joaquin Valley farms and millions of Southern California residents.
The sinking Central Valley threatens to curtail as much as one-fifth of water deliveries through the vital California Aqueduct to San Joaquin Valley farms and millions of Southern California residents. (Dan Brekke/KQED)

The NASA images also show the separate Delta-Mendota Canal in the valley has dropped 22 inches, threatening supplies to 2 million residents and 3 million acres of farmland, officials say.

Jones said the satellite images show thousands of existing wells within a few miles of low areas.

The state Department of Water Resources said it would like the Legislature to give it authority to establish zones where pumping is limited, she said.

Signs of the sinking land have been visible since the 1920s. In the current drought, farmers in the agriculturally rich San Joaquin Valley relied heavily on well water because little rain and snow had fallen to fill reservoirs.

Chris White, general manager of the Central California Irrigation District, said he would prefer a more targeted approach because each problem caused by over-pumping is unique. He said his district has spent $7 million to repair a buckling canal and a waterlogged bridge.

“A big part of this answer is not adopting legislation that handles this in a one-size shoe fits all feet,” said White, adding that he had not reviewed he state’s latest plan. “They will require understanding each of the specific problems and developing the solutions.”

Central Valley’s Sinking Land Threatens Vital Canals 9 February,2017David Marks
  • Hillary Clintub

    New Orleans and south Florida are also experiencing subsidence…but for slightly different reasons. All of them are affected by subsurface water levels, though.

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