MERCED — The ground is sinking under the Eastside Bypass and surrounding area because of groundwater pumping, according to the California Department of Water Resources.
Regional irrigation officials said if the problem is not addressed quickly, it could cause significant damage.
The banks of the bypass, a flood control channel used to manage flows on the San Joaquin River, have been sinking as much as five feet in some areas over the past two years.
The sinking has affected adjacent irrigation districts. The San Luis Canal Co. and the Central California Irrigation District have seen canals begin to sink.
"The major concern is the reduction in flood capacity in the bypass channel," said Chris White, general manager of CCID. "If we had a release like in 2006, it's possible you'd see some localized flooding."
Area farmers rely heavily on groundwater to irrigate their crops, which has depleted the aquifer, White said. In response, growers have drilled deeper and deeper wells, some as far down as 900 feet.
As a result, the ground underneath parts of the channel is dropping by about six inches a year, according to data from the Federal Bureau of Reclamation. The affected area runs diagonally from West Sandy Mush Road south under Highway 152 to Road 9 in Madera County.
Over recent months, local farmers and irrigation district officials have started a project to address the problem, White said. Now they're scrambling to complete it before the next wet season, which comes on average about once every three years.
"We're getting proactive," he said. "We're thoroughly behind helping these landowners solve this problem in a big hurry. I have a high level of optimism that this can be done."
The plan is to divert some of the water from the bypass into groundwater recharge basins, White said. At the same time, farmers would switch back to using shallower wells.
With only about 30 farmers in the affected area, correcting the problem won't be cheap.
To start, farmers in Madera County, a little more than half of them in the affected area, agreed to pay for an $80,000 technical study. The county Board of Supervisors and regional irrigation districts donated $20,000.
In Merced County, the cost of the study is about $45,000. Farmers have not committed to funding it. However, irrigation districts and the Merced County Board of Supervisors have put $25,000 toward the effort.
"I don't think it's something that the county of Merced should take on itself, but I fully believe we need to be a part of the solution," said Supervisor Jerry O'Banion, who represents the region.
This problem is new to the area, said Brian Smith, an engineer with the state Department of Water Resources who specializing in flooding. About 15 years ago, the banks of the channel had to be raised in an emergency project.
Sinking has been a problem in the valley since the beginning of groundwater pumping for irrigation, Smith said.
"Periodically we go through this during periods of drought," he said. "In some cases it's permanent, in some cases it's not."
Reporter Joshua Emerson Smith can be reached at (209) 385-2486 or firstname.lastname@example.org.