It isn’t obvious to the naked eye, but the San Joaquin Valley is sinking, and it’s slowly destroying key parts of the agricultural infrastructure as it goes.
Each year, as farmers and ranchers pump water from the aquifer underlying the Valley to supply their crops, the water they remove leaves gaps in the miles-deep, sponge-like structure of soil that has built up there over millions of years. Soil is merely dirt and rock, and without the water that was imbued in it, it collapses and compactifies in a process known as “subsidence.”
Drought Speeding Invisible Sinking
Subsidence is not a new phenomenon. The floor of the Valley has been falling for decades, with some areas on the west side having fallen more than 28 feet from their original levels since the 1920s when farmers began tapping the water beneath their feet, according to a report by NASA Earth Observatory. The effect, however, is becoming far more pronounced as more and more independent agriculturalists, irrigation districts and cities depend on groundwater to meet their needs during the worst drought in California history.
The ground in some areas of the South Valley – centered in the middle of the former Tulare Lake Basin near Corcoran – is falling at a rate of up to a foot a year. In the stretch between Pixley and the Kern County line, the subsidence is so bad the Friant-Kern Canal has sunk to the point it now carries just a fraction of its original capacity.
“The canal is just going down into a hole,” Chris Hickernell, general superintendent for the Friant Water Authority, said during a recent interview with KPIX CBS SF Bay Area. “But it’s the whole region around here that’s kind of settling in, and a lot of people don’t look at it that way because the grapes aren’t any lower and the pistachios aren’t any lower.”
The Friant-Kern Canal, which flows from the Friant Dam at Millerton Lake on the San Joaquin River north of Fresno, is gravity fed, relying on a steady downhill slope to carry water to 15,000 family farms, irrigation districts and cities. The intent of the canal when first conceived in the 1940s was to alleviate groundwater pumping in the South Valley by moving water from the wetter northern regions.
But subsidence is slowly choking the canal. “To convey this water south through this section, we’ve lost 60% of the carrying capacity,” Hickernell said.
The process is likely to get much worse. Spring rains meant an increase from 15% to 20% for the Friant Division 1 water allocation from the Bureau of Reclamation this year, but what seems like a blessing isn’t.
“Although this is all good news compared to what we thought might happen, the previous three months of reduced Delta supply cost Friant Contractors more than 200,000 acre-feet of water, which will undoubtedly result in a similar volume of water being pumped from the Valley’s stressed aquifers,” Jason Phillips, CEO of the Friant Water Authority wrote in July. “This highlights the reality that the current water infrastructure and environmental regulations are failing the people of California, and both major investments and major reforms are needed.”
Subsidence Could Last Centuries
Reducing the volume of water pumped from the aquifer – even stopping altogether – won’t be enough to keep the Valley floor from falling into the hole groundwater users have dug. A recent study at Stanford University shows the ground will continue to sink here for hundreds of years because of the damage already done.
The study simulated 65 years of subsidence using data gathered in and around Hanford from remote sensors, pumping logs and input from water managers in the area. Researchers found without replacing the water, the problem will continue.
“If you don’t get these water levels to come back up, then the land is going to sink, potentially tens of centimeters per year, for decades,” said Matthew Lees, a geophysics PhD student and lead author of the study, which appeared June 2 in the journal Water Resources Research.
On the other hand, if a concerted effort is undertaken to replace the water removed over the last century, the subsidence should stop within a few years, the study found.
“But if they (groundwater levels) go up, you can get rewarded very quickly,” Lees said. “You almost immediately improve the situation.”
Going With the Flow
While the Stanford study did not mention the Friant-Kern Canal specifically, it follows that fixing the canal’s flow problem could potentially bring more water to regions where groundwater is the main source.
To address the falling canal, the Friant Water Authority is overseeing the construction of what is essentially a new 10-mile stretch of the Friant-Kern Canal in the area near Pixley where the dropping of the waterway is worst.
Construction of the Friant-Kern Canal began in 1949 and was completed by 1951, but within 25 years subsidence had dropped the canal far enough that portions of it had to be rebuilt during the mid-1970s. Concrete skirts that line the canal were raised by six feet, and the feed pipes that supply water from the canal were rerouted to accommodate bridges over the canal that had to be raised.
Since then, the reduction in the canal’s carrying capacity has continued to dwindle. Designed for a capacity of up to 5,000 cubic feet per second (cfs), the canal is now only able to deliver 1,600 cfs. If the problem wasn’t being addressed – and it is – another 10% loss of flow would be expected within the next three years.
No Simple Fix
This time, however, an upgrade isn’t enough, and the plan is to build a new 33-mile section of the canal between mileposts 88 and 121. The new section parallels the existing waterway, and as sections are completed, the canal’s flow will be rerouted. The new canal is also needed since the bed of the old one has degraded in the 75 or so years since its construction.
“There’s a lot of leaks,” said the construction manager interviewed by KPIX. “There’s a lot of squirrel holes and everything, so what happens if they hit one of those holes, it creates a leak, and that’s what we’re dealing with now.”
Phase 1 of the rebuilding project is now eight months along, with crews constructing a new 10-mile portion of the Friant-Kern near Pixley, downstream of the existing Avenue 136 bridge and downstream of a farm bridge south of Avenue 64. The first phase of construction will replace what the Bureau of Reclamation says is the “worst pinch point” along the canal’s route. When completed, flow in the canal will be returned to the 4,000 cfs it originally carried.
“You don’t really realize how big some of these waterways are until you are standing in it, and either they’re building them or they are empty,” Hickernell said.
Paying for the New Friant-Kern
The Friant-Kern Canal was built as part of the Central Valley Project (CVC) a series of dams, reservoirs and canals up and down the Valley intended to alleviate flooding, provide water to parched areas, generate energy and improve conservation. The CVC is still overseen by the US Department of the Interior’s Bureau of Reclamation, and it, along with the state’s Department of Water Resources, the Friant Water Authority and groundwater service agencies – local boards tasked with preserving the diminishing aquifer – will be paying the bill for rebuilding the canal’s sunken portions.
The Eastern Tule Groundwater Sustainability Agency (ETGSA), which caused much of the subsidence in the area by over-pumping, agreed in 2020 to pay for a large portion of the $500 million cost of the reconstruction. The ETGSA covers 162,000 acres, more than half of which depend on groundwater and lie outside an irrigation district.
The ETGSA could have agreed to pay a one-time lump sum of $125 million to cover the portion owed by its members. The proposal was put forth in December of last year, and this summer, the ETGSA membership voted to extend their payments over several decades, adding $75 million to what they owe.
The lump fee would have been covered by a $140-per-acre one-time assessment. Instead, water users in the ETGSA will see 92% of the water fees they pay transferred to the Friant Water Authority’s coffers.
Despite the cost, the project must be completed or the Valley will continue to lose precious water in an ever-building cycle or pumping and sinking. Further, the new canal’s design will prevent some of the problems the old one experienced.
“The design of this canal, the new one, is taking away all the bridges, and then siphons underneath the road, so we don’t have any obstructions through bridges or any of that stuff,” Hickernell said.
Keeping the Friant-Kern flow optimal will also be key to stopping the fall of the Valley floor.
“If we can repair this, get the capacity back to carry the water, all of these spreading grounds in these districts are investing money in, we can supply these things and we can recharge the ground tables,” Hickernell said.