Canal plans to bypass subsidence with 30-mile parallel path
Friant Water Authority proposes building parallel canal to Friant-Kern Canal along 30 miles in southern Tulare County
By John Lindt
Sierra2theSea News Service
TULARE COUNTY – As the old saying goes, if you can’t go through something, go around it. And at an estimated cost of $357 million, the Friant Water Authority (FWA) is contemplating a 30-mile parallel canal to circumvent the portion of the Friant Kern Canal (FKC) that has been negatively affected by subsidence.
Under the “Capacity Correction Project” the FWA is attempting to find a solution to the portion of the FKC that has lost 60% of it’s conveyance capacity, due to subsidence. That in turn has been caused by several years of vigorous groundwater pumping by nearby farms.
Subsidence is the removal of water from very fine clay-like pore space in the subsurface, which also removes its internal strength and over time compresses and the surface of the land. During the drought when surface water supplies were limited or unavailable, regional farmers, cities and others turned to groundwater. Tulare County was identified as one of the most overdrafted counties in the state in 2015.
While the FKC carrying capacity has been compromised by various factors, including subsidence, since it began operations in 1951, the scale of the problem driven by rapid and severe land subsidence in the Corcoran/Tulare Basin areas is another matter.
In 2015 and 2016 land elevations dropped by two feet near Corcoran and there was a problem moving water near Deer Creek. In 2017, according to a press release from the FWA the canal dropped five inches in five months near Avenue 96 between Terra Bella and Pixley. The results came from an initial survey in April 2017 to measure subsidence along the Friant-Kern Canal, they expected to see impacts from the recent drought. What they measured in some places was a nearly three-foot drop in the canal elevation. Friant Water Authority chief operating officer, Doug Deflitch, said that max capacity for the FKC is 9,000 cubic feet per second. Because of subsidence that has slowed down to 1,700 cubic feet per second.
Water managers say, “There is no way to operate the canal to eliminate impacts to water users caused by this amount of subsidence.“
Also in 2017, Jason Phillips, Chief Executive Officer for the Friant Water Authority added, “The continuing subsidence issue is why FWA is exploring possible funding mechanisms for bringing the Friant-Kern Canal back to its designed operational potential. A fully functioning canal will help achieve the groundwater/surface water balance the Friant-Kern Canal was designed to maintain, and lessen the impacts of subsidence.”
The water in the canal feeds not just farms but whole communities, many disadvantaged, and their drinking water. In wet years it is this canal that allows farms to replenish groundwater to help manage the subsidence problem.
After some serious study of alternatives, Friant is now focusing on the idea of building a parallel canal to the east of the existing Friant Kern near Porterville. Friant Water Authority’s Chief of External Affairs Johnny Amaral says the board has selected this 30-mile parallel canal as its “preferred alternative” to fix the problem. Amaral joined the organization in March.
This is a new development as previous approaches included pushing more water down the canal. In 2017 Deflitch said there are three phases to address the issue. The immediate phase was to look at the bridges that cross the canal. Because of subsidence water pools at the portions that have sunk into the ground which raises the water level. The FWA assessed the soundness of the bridges to determine if water can go over them, which would allow for additional conveyance and for customers to receive their water.
Deflitch says the median phase was to raise the bridges over the canal. The long-term phase was similar to what the Bureau of Reclamation did after a drought in 1979 which was to raise the liner of the canal which raises the embankment. The FWA chief operating officer admitted that replacing the canal liner is a project that would cost hundreds of millions of dollars.
South Valley water contractor Dan Vink, whose water districts represent 400,000 acres in this area, says the parallel option is considered superior to building new pumps to move water above the sinking structures rather than engineering a new canal that can withstand future sinking.
A solution won’t come cheap. Amaral says the official estimate for this 30-mile canal is $357 million.
How to fund it? Vink argues “multiple sources are the only way” noting the project is federal and can’t arguably be fixed with only state funds. “We need locals and farmers themselves” to help pay along with Federal dollars, he says.
Amaral says federal representatives like his old boss Devin Nunes and Kevin McCarthy who represent some of this region for the GOP and Diane Feinstein, a long term senate Democrat from California, are all on board and supportive.
“We are looking at cost sharing among all” agrees Amaral. Still state Senator Melissa Hurtado has authored a $400 million bill that may pay for part of the project.
The time table is short but doable expects Amaral.
“We want to be moving dirt by the summer of 2020.”
Vink says while all eyes are on repair of the Friant Kern water project, yesterdays big project Temperance Flat “has taken a back seat.” Vink is skeptical that Friant contractors will be able to afford Temperance Flat water in any case.